DIY LED driver for reef lighting

[kcress]

kcress, Where are you getting the 9.87 volts from? So you think that by chance I all the 'high resistance' LEDs made it to the same string and I am just seeing tolerances i the LEDs?

Sorry Fish! 19.87V. I dropped the "1", and after adding them up several times to make sure. :sad2:


And, Yes! You have a rogue string there. ;)

[TheFishMan65]

Well it just happens that I got an order of 24 Royal blue LEDs in today (actually a lot more, but that was my share). I will find a low one and switc it out.

[TheFishMan65]

I replaced the 3.48 and 3.43 with 3.16s and the current went upto 0.80 amps.

So IMHO if we intend to turn down the voltage supply to be 1/2 volt over the voltage string it would be wise to bin the LEDs. Worst case I would have had 6 at 3.6 volts (18.96 volts) and 6 at 3.48 (20.88 volts) almost 2 volts difference. And that was only at 0.3 amps.

[kcress]

Yes, you'd want to voltage bin if you wanted the very least supply voltage to successfully supply multiple drivers.

I'd swap with the other chain though - not use the new ones. Otherwise your other chain will always be way lower perhaps, than any other chains.

Seems you now have an understanding of your original issue. :thumbsup:


Just to reiterate: To make any of these binning decisions you need to drive ALL the chains at exactly the same current. Otherwise your LED to LED Vf measurements don't mean a thing. As the current changes the Vfs all change. When you originally swapped around strings across a fixed voltage source, instead of a fixed current source, all the Vfs of the string having aggregate-sum Vf issues hid itself by distributing the available supply voltage across all its LEDs. That shows very similar Vfs between a low string and a high string. Which is confusing.

[Dejavu]

This thread has been nominated for December's thread of the month! You may vote here (http://www.reefcentral.com/forums/showthread.php?t=1941578). Good luck:beer:

[der_wille_zur_macht]

Wow, I am honored. Thatnks evefyone who has contributed so far and made it a great thread.

[shackscs]

I just voted!!! I have learned waaaay too much from DWZM and everyone else on these LED/Driver/controllerthreads to not let my vote count!

[Obi-dad]

Got my vote - the cat4101 drivers rock! Thanks to dwizum and the other contributors

[S&KGray]

I just voted!!! I have learned waaaay too much from DWZM and everyone else on these LED/Driver/controllerthreads to not let my vote count!

+1

My CAT4101 drivers are assembled, still working on my prototype fixture and need to get started on the controller.

:cool:

[der_wille_zur_macht]

People interested in DIY drivers (or LEDs in general) should check out this magazine from Digi-key:

http://reference.digikey.com/TZ/lighting/2010/WebProject.asp?BookCode=dtz10flx&from=2#

There's an article on page 56 that talks about cap selection for switching regulators used to drive HP LEDs. While the CAT4101 design is not a switching reg, it's still an interesting read.

The article on page 54 discusses analog vs PWM dimming but is pretty short and doesn't go into a lot of detail.

[SpacedCowboy]

Got my vote - the cat4101 drivers rock! Thanks to dwizum and the other contributors

(steps out on stage, takes a bow, blushes, steps back into the shadows :) )

This thread got my vote too, unsurprisingly, but I thought the other two were interesting...

Simon

[der_wille_zur_macht]

(steps out on stage, takes a bow, blushes, steps back into the shadows :) )


And you deserve it! Without real EEs like you, kcress, and stugray to keep me on track early on, this thread would have probably fizzled and died.

I'm starting to think about drivers for very large tanks, i.e. making a DIY version of the Meanwell HLG series. What features would be important in a driver like that? I'm guessing we want it to drive lots of LEDs, provide for dimming, and operate efficiently. Theatrus contributed a design a bunch of pages ago for a driver like this (and I hope he gives us an update) but I think there may be a gap in terms of a design that's simpler than his (and I mean that as a compliment).

The main thing I'm struggling with in envisioning this design is the DC power source. In very large arrays, power factor correction seems to become important. Do we really want to design an exact copy of the HLG, which has an integrated PFC-corrected DC supply and can be plugged right into a wall outlet? Or, do we continue the trend here of designing a simple DC-DC regulator that requires an external power supply? The catch here seems to be that while you can occasionally grab as PFC-corrected 24v supply for a reasonable price on eBay, that's a pretty low voltage to run a large array with, and finding larger PFC-corrected supplies is harder and very very expensive. Meanwhile if we ignore the PFC feature, there seems to have been a load of 48v, 350w Meanwell supplies on eBay lately for around $40 - $50, which is actually cheaper-per-watt than the beloved bargain-bin 24v 6.5A supplies so many people use.

Decisions, decisions...

[TheFishMan65]

I have been following the coral growth one and some of it gets beyond me, but very informative for what I follow.. I found it very interesting that two responses in November got the refugium tips on listed as thread of the month (anybody know how they get nominated). I am in the process of reading and find it very interesting.

But you got my vote too.

[SpacedCowboy]

And you deserve it! Without real EEs like you, kcress, and stugray to keep me on track early on, this thread would have probably fizzled and died.



Oh, I wouldn't claim to be an EE. I'm just an aging physicist :)

I'm starting to think about drivers for very large tanks, i.e. making a DIY version of the Meanwell HLG series. What features would be important in a driver like that? I'm guessing we want it to drive lots of LEDs, provide for dimming, and operate efficiently. Theatrus contributed a design a bunch of pages ago for a driver like this (and I hope he gives us an update) but I think there may be a gap in terms of a design that's simpler than his (and I mean that as a compliment).

The main thing I'm struggling with in envisioning this design is the DC power source. In very large arrays, power factor correction seems to become important. Do we really want to design an exact copy of the HLG, which has an integrated PFC-corrected DC supply and can be plugged right into a wall outlet? Or, do we continue the trend here of designing a simple DC-DC regulator that requires an external power supply? The catch here seems to be that while you can occasionally grab as PFC-corrected 24v supply for a reasonable price on eBay, that's a pretty low voltage to run a large array with, and finding larger PFC-corrected supplies is harder and very very expensive. Meanwhile if we ignore the PFC feature, there seems to have been a load of 48v, 350w Meanwell supplies on eBay lately for around $40 - $50, which is actually cheaper-per-watt than the beloved bargain-bin 24v 6.5A supplies so many people use.

Decisions, decisions...

Ok, so let me play devil's advocate a little here: the only real advantage I see to this is to have a smaller (possibly even a single) driver; this leads to less circuitry, and it's possibly cheaper to do. I suppose if you're using a single PSU, it may edge the efficiency too.

On the other hand, there are several drawbacks:

Dimming controls are less precise
I really don't like the idea of getting involved with line-level power. It's perfectly safe when it's perfect. It's potentially lethal otherwise, and my track record is *ahem* not exactly 100% perfect first time...
The larger single PSU means you need to think about power-factor correction, compared to just soft-starting the individual PSUs using a controller{*}
The single PSU is a single point of failure for the entire system
The voltages involved with longer strings make the circuit design more complex, AFAIK the simpler drivers won't go that high. Admittedly, it's not significantly more complex :)


... just off the top of my head. I guess I'm not sure it's worth it (to me), but I guess everyone has their own preferences... Example: I want to do things like sunrise/sunset-across-the-tank (purely for aesthetic reasons, I realise :) ) by varying the intensity of the strips at lights-on / lights-off.


{*} It bugs me that power-factor-corrected PSUs are so expensive. As far as I know they just put an inrush-current limiter (http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=656273&k=cl-50) immediately after the bridge rectifier and Bob's your Auntie's live-in-lover. Total cost: about $3. A technical-sounding name makes for great marketing... [sigh] It's a pity it has to be done within the PSU circuit...

Simon

[kcress]

Willie; I can assure you you do NOT want to go anywhere near building a DIY Meanwell. Hideously dangerous and actually very hard. They also require equipment no typical DIYers would possess. They land you in the same place DIYing a 55gal aquarium does - that is, you will pay more for it than if you just bought it, never mind the hundreds of hours you'd spend doing it.

If you wanted to step it up, I'd suggest a multi-channel board with Boost converters. Feed it 24Vdc from a PFC 24V supply, (just standardize on that input voltage), and have it drive many more LEDs - like 12 or 15 to improve on Meanwells. That way you can use a junker 24V supply if someone only wants to run a smaller rig.

Stick with single strings to avoid the balancing requirements.

Include a 0.1 ohm resistor, on board, to end the tyranny of series current meter hook up. Design it with actual test points across the resistor for easy clip-on.

If you want to add nice features, you could add a local supply for dimming, to end the wallwart nuisance. You could also add a fan driver to ditch yet another wallwart. You could consider a temperature monitoring option too. It could control the fan or throttle back the string in a fan failure situation.


SpacedCowboy; Physics.. My favorite subject. I even minored in it. The PFC stuff is not inrush limiting stuff. It can limit inrush if designed to. It is much more than that. Often another active controller is even involved - hence the higher cost.

[der_wille_zur_macht]

Ouch! I've been shot down! :lol: Honestly I appreciate the honest feedback. It strikes me that there's a void in the sense of driving large arrays "conveniently," but maybe it's not worth the effort anyways. I guess I feel like with the CAT4101 design "done" and so widely used, I'm looking for the next logical step in terms of our DIY driver efforts.

kcress, I like the idea of some of the functionality you're describing. I have to admit I'm hitting another wall in terms of my understanding of switching regulator topologies. You may recall that the NCP3066 design I started this thread with was a boost topology. I had a major complaint with that design, which was that the dimming performance sucked. It basically acted like it could only dim down to a power level equal to Vin, if that makes sense. When the dimming signal was full off, the array still remained brightly lit. Thing is, I don't know which of the following caused that:

1) Was this simply a problem with my implementation or use of the chip? i.e. did I have some stupid flaw in my design?
2) Was this a problem unique to this particular IC? i.e. does it just have terrible dimming performance when used in a boost topology? I actually tried the same IC in a buck mode and it worked just fine, and would dim to true zero (the LEDs would turn off with a zero duty cycle PWM signal).
3) Is this problem going to be present in any boost design? Can a properly designed boost regulator being controlled with a PWM signal actually dim in a nice smooth linear fashion all the way down to zero?

Regarding the other features you suggested, maybe I'm taking a unique approach to this, but I'm completely used to having some form of an Arduino on any tank I'm working on, so stuff like fan control I'd just do there. I do like the idea about actually generating the voltage to drive the fan on the LED driver board though, for just the reason you said - it eliminates the nuisance of having yet another wall wart on every single tank. What do other people think about these functional ideas? Which of them would be ideal to have incorporated with the driver(s) vs. built into some separate control unit?

[Foosinho]

Oh, I wouldn't claim to be an EE. I'm just an aging physicist :)
I'm an EE! Computer design specialization, to boot.

No education in power, tho. I had to do some research to understand how to build my own power supplies for LV DC circuits. (And those are really pretty simple circuits.)

I really don't like the idea of getting involved with line-level power. It's perfectly safe when it's perfect. It's potentially lethal otherwise, and my track record is *ahem* not exactly 100% perfect first time...
Bawwwwwwwwk bawkbawkbawkbawk!

Just kidding. :bounce3:

I've done some line-level design as a part of my homebrewing stuff. It was pretty straightforward stuff, tho, since it's basically just controlling SSRs. I would be willing to look at this idea, despite not having a lot of experience, except for the fact that I'm broke right now AND moving to a new house (and selling my condo) this winter. What can I say - I love DIY. The journey is as important as the destination. :)

[kcress]

Willie; Probably the issue with dimming your boost driver was that there are buck, boost, and buck-boost drivers. In some cases the topology completely bars the driver from ever shutting the supply off entirely. The whole point is dedicated to elevating the output 'above'.

It may be you need a buck-boost controller because, by definition, they have to be able to shut it off entirely (the buck aspect).

You should do another driver chip survey as many more have appeared since you did that last one.

[der_wille_zur_macht]

Keith, are you referencing the so-called SEPIC (i.e. two inductors) topology? The NCP3066 could be configured like that but I hadn't taken that route in my earlier effort. theatrus took that route with his microcontroller-brained LM3404 design and that particular chip is looking really appealing right now.

Surveying chips right now. And still scratching my head over functionality. I like to keep things modular/expandable so I'm trying to decide if it makes sense to put fan control and/or moonlight control on an LED driver, or if they should be a separate PCB. I'm wondering if we'd want something you may only want one of (fan/moonlight control) on a PCB with something you may want different amounts of (LED control).

[der_wille_zur_macht]

I'm thinking about a slightly different tangent. I'd like to put an I2C "front end" on one of these drivers for dimming control. I'd like to do it in the simplest way possible (i.e. I don't want to embed a microcontroller on the board!). Anyone have any thoughts?

One possibility that I'm not QUITE sure about would be to borrow fishman's concept of putting a pot on the Rset pin, but use a digital pot with an I2C interface. I'm thinking of this because I'm coming up with very little in terms of a simple I2C PWM chip to dim via the EN pin, meanwhile it looks like there are I2C digital pots out there that are dirt dirt simple and cheap. One thing I'm not sure about is the current rating required for this sort of purpose - most digital pots have a very very low current limit on their "wiper" pin.

[kcress]

Yes a SEPIC will do it or I believe some B-B controllers have full dimming.

As for I2C I think your only option is a local micro if you can't use a digital pot. Wait.. You could use an I2C DAC too.

Yes, put the other options on the boards too. You don't actually have to stuff them! But they're there if someone needs them. 24V will already be on the board so certainly the 10V dimming and 12V fan supplies should be carved out of that 24V.

[der_wille_zur_macht]

I found what I was looking for. The DS1050 from Maxim is an I2C chip with one PWM output and it even has hardware address pins so you can have several on the same network. Perfect - one of these can be slapped in front of a CAT4101 (or any other PWM LED driver) to turn it into an I2C-dimmable driver.

I don't think I'm going to follow through with the new switching reg design after all, at least not right now. theatrus's design is probably about what I would have come up with so it seems like the "gap" I thought there was isn't actually there. I've got a few other projects I want to work on right now anyways. Stay tuned. :)

[DustinB]

Nice find DWZM! This should prove useful even beyond the LED driver. Unfortunately, it doesn't look like they provide it in a PDIP package.

[Foosinho]

Nice find DWZM! This should prove useful even beyond the LED driver. Unfortunately, it doesn't look like they provide it in a PDIP package.
That is a seriously useful chip. +1 on that "nice find" sentiment!

[TheFishMan65]

For those the have it working what wil dawn and dusk look like with only 31 steps (instead of 255). The DS1050 only has 5 bits of resolution for the PWM.

[DustinB]

Good catch. How well can you see below a 3% increase/decrease?


13. The DS1050 is a 5-bit PWM. The output duty cycles of the device range from 0% to 100% in step
sizes of 3.125%. The “Set PWM Duty Cycle 100%” allows the PWM output to be set to full-on.

[der_wille_zur_macht]

FWIW I'm currently dimming with a Typhon, which I've dumbed-down to step in 100 increments - so I'm already below a standard Arduino's 8 bit resolution, and it looks fine. If you're watching when a step happens you can certainly see it, but it's not a huge jump. I agree that the 5-bit resolution on this part is not ideal but for my intended application (which is NOT dimming "main" lights on a fish tank to simulate sunrise/sunset in this particular case) it will actually be higher resolution than I need.

The package for this part is indeed TINY but certainly not unmanageable IMHO.

[DustinB]

I take it you have probably seen this before? http://www.nxp.com/#/pip/pip=[pip=PCA9685]|pp=[t=pip,i=PCA9685]

It's fairly cheap but no one seems to stock it.

[der_wille_zur_macht]

Yeah, I've seen that - if I needed 16 channels I'd probably use one of those, but that's an even more insane package. Same pin pitch but eleventybillion more pins so it's easier to mess up (IME). Plus like you said they're hard to get.

[Foosinho]

Good catch. How well can you see below a 3% increase/decrease?
You can increase the (effective) resolution by staggering the PWM increases. IE, if you have 5 LED chains, instead of incrementing the PWM by one on all of them simultaneously, you round-robin and increase just one (just do it more frequently). That would give you 155 (5*31) steps in your ramp, instead of 31.

EDIT - and you'd only be using something like this if you had more PWMs than the Arduino (or whatever other controller you were using) had. In which case the software "fix" is almost zero cost.

[TheFishMan65]

Just wondering. There are probably a millions ways around this.
- have multiple CAT4101s driving the same chain and alternately turn them up.
- have a small step and a big step. Every time the small step is about to wrap increase the big step by one.
- Maybe you could have the controller alternate a value for a while. Write X% then write X=Y % then X, then X=Y for a second or 2.
Not sure any of it is needed though.

[kcress]

Remember we can only see a 50% change in brightness so 31 steps is probably adequate.

[TheFishMan65]

kcress, I beleive that is a yes and no. You won't notice if you close your eyes and some adjusts it and then open them, But I bileive (and DWZM confirms above) that if you are starting at it you will notice a 1 partin 100. Unless the arduino does not make a smoth step from one level to th next and that is what he is seeing.

[kcress]

Interesting... I bet you're correct. I believe it's if someone continually turns down a light you'll say, "I see a change" once a 50% change occurs. But I guess a step change IS noticeable.

[der_wille_zur_macht]

I will concur. If I'm watching when it makes a discrete 1/100 change, I can see it. If I look away, I bet it would take many steps at that resolution.

At any rate, as I mentioned above, for my individual project, it's kind of a moot point, since I only need 27 steps. :)

I *am* interested in the general application of this concept though - putting an I2C front end on one or more of these drivers. The other approach I thought of was to put an I2C digital potentiometer in series with Rset (yes, despite all my comments about how I think it's a bad idea to put a pot in series with Rset) but I can't find a digital pot that even comes close to the current capacity. I'm guessing there are other ways you could do this (standard issue DtoA converter? op amp on a digital pot?) but I'm left scratching my head...

[inky]

I could be wrong DWZM, but isn't the voltage for RSet at 1.2V, therefore the current is minimal.

I have been thinking about using a digital pot instead of PWM, just never got very far with it........ Is efficiency better to change the current instead of varying the mark:space ratio of PWM. Plus, would the lifespan of the LED be lengthened by not switching high currents, but more of a constant current.....

Ian

[DustinB]

Yeah, unless I'm reading the datasheet wrong, there is a 400 to 1 ratio for LED/RSET. That should put the current around 2.5mA when the LED current is a full 1A. Voltage should never exceed 1.23v.

[der_wille_zur_macht]

Dustin, some of the digital pots I've looked at have separate Vcc and GND connections, discrete from the two or three "pot" connections, so the operating voltage for the IC is supplied separately from the voltage through the potentiometer. So you'd supply the IC with GND, 5v, SDA, and SCL and then connect two of the three potentiometer terminals into the Rset trace.

The devices I've looked at have current limits in the 1mA - 2mA range, so despite the low current we'd be at or near the limit. I may just go ahead and try it anyways, to see how it works.

Part of my frustration here is that Analog Devices seems like the best manufacturer for digital pots, but Mouser doesn't carry Analog Devices products. :mad: Mouser has good prices on everything else I need so I don't want to go make a digi-key order for one 50 cent part...

[der_wille_zur_macht]

Also, not that I want to shill, but the Thread of the Month poll that Dejavu mentioned back a page closes tonight. So go tell all your friends to vote for their favorite thread! :D

[DustinB]

Some of the maxim-ic ones I saw on mouser appeared to be rated at up to 25mA. They were only single output and, unless I'm mistaken, showed they wouldn't vary a great deal from their rated resistance. ie: 60-100%, not 0-100%

If someone can locate a good option, most of these seemed to have a 128 step range, give or take.

[TheFishMan65]

I looked at digital pots and got lost too. It looked to me that they acted more like a D/A and set the voltage between the supply and ground. Which is why I went with the analog pot and PWM dimming.

[der_wille_zur_macht]

Dustin, can you post product numbers? I should add that I'm trying to stick with reasonable packages. SMT is fine but I want pitch at least .65mm.

Fishman, it looks like there are a few different topologies for digital pots. Looks like most have a resistor network inside, and switches that control which of the resistors are connected to a "wiper" pot. Some only expose one end of the resistor network and hence would act a lot like a DA I suppose. Others expose both ends of the resistor network and hence truly emulate a "real" passive pot with three terminals - there is no voltage or signal present on the "wiper" unless you connect something to one or both ends of the resistor network. This is my first attempt at learning about/using digital pots though so I'm definitely not an expert.

[TheFishMan65]

I guess I did not look into enough of them. Thanks for the information.

[DustinB]

This one just meets your size: MCP4018T (http://www.mouser.com/ProductDetail/Microchip-Technology/MCP4018T-502E-LT/?qs=sGAEpiMZZMuD%2f7PTYBwKqbA3OlZty8IBbO7z%252bclmjF0%3d)

You are correct on the currents, I was confused. The ones I looked at only had a 2.5mA rating on the resistor circuits, 25mA on any output pins. The one listed above does have 128 steps and is a full range 0-100% pot. It may be acceptable for current settings up to 700mA or so. RSET should be around 1.75mA at 700mA LED current, but hits the max 2.5mA at 1A LED current.

You'd really think it would be easier to find something like this with a higher current rating...

[der_wille_zur_macht]

This one just meets your size: MCP4018T (http://www.mouser.com/ProductDetail/Microchip-Technology/MCP4018T-502E-LT/?qs=sGAEpiMZZMuD%2f7PTYBwKqbA3OlZty8IBbO7z%252bclmjF0%3d)

That's one I looked at. It would work for the application of dimming the CAT4101 but I have another application where I want a digital pot with both ends exposed - that chip only exposes one end and the wiper, it connects the other end to ground or leaves it unconnected depending on which variant you order.

[bluebayou]

My planned tank: 180gal or 200DD, both are 1,728" area coverage.
LED Qty: Not totally sure but well over 100. 144+?
I plan on controlling with a Typhon

I would need to solder 24+ 4101 boards. How many power supplies would be required? I am a beginner at all this but I am imagining a big stack of ps's.

Does the new Mean Well HLG drivers make more sense for my build? I'm trying to figure out what makes the most sense. The granularity of the 4101s may or may not be worth it, I don't think I understand all of the ramifications of either solution.

My idea is to have the LEDs on individual heatsinks and sitting on opposing rows of L channels forming slots then making a big panel of slots such as this:
____________________________
|____________________________|
|____________________________|
|____________________________|
|____________________________|
|____________________________|
|____________________________|

Using this method I can slide the individual LCDs all over the place creating concentrations or gradients if necessary as well as individually tilting LCDs to prevent overspill ect. The best thing is that it is completely adjustable with the push of a finger not to mention easy to replace burned out LCDs ect.

What do you all think?

[TheFishMan65]

If you can find a 24 amp 24 volt supply (OK a little larger current 28) one would do it. Or if you run at less than 1 amp. You will probably need 2-3 supplies. I am guessing 3-4 HLG
IIRC HLG are close to $100 so $3-400 that way
A Cat4101 circuit runs $3-4 so $72 to 96 here. If you can find power supplies on ebay maybe $40. If not new probably $100.
So I would guess costs are about even.

[der_wille_zur_macht]

For 144 LEDs you'd need 24 CAT4101 circuits. No one's putting a single CAT4101 on a board (that I know of). For instance, my design uses 3 of them per PCB, so you'd need only 8 boards. If you stick with LEDs that are on the lower-end of the Vf spectrum, which should be easy-ish to do, you can probably sneak 7 LEDs on each CAT4101 (sum of Vf basically needs to be 24.5 or lower). In that case, you'd need 21 circuits, or 7 3-up boards.

Regarding power supplies, FishMan is about right - you need to budget your LED current plus about 20 - 30 percent. If you target 700mA drive current, you're talking about needing roughly 20A. You'll likely end up with multiple supplies as one single supply that large will be hard to find and/or insanely expensive. You need to decide if you care about power factor correction, as well.

I agree with FishMan on cost as well. The HLG drivers are very good in terms of cost per watt of output, so they're hard to beat in that respect on a large tank. If you go with HLG drivers, the biggest "issue" will be dealing with parallel strings and the fact that you'll only have a few discrete groups of LEDs for dimming. If you go with the CAT4101 design, you'll have much greater resolution for control (smaller groups of LEDs) and won't have to deal with parallel strings, but you WILL have to deal with having lots more "things" involved with driving your LEDs. It's a tradeoff based on your preferences, I don't think there's a clear one size fits all answer.

Back a few posts I was pondering the concept of trying to generate a DIY design that was equivalent to an HLG. I think this would be easy to achieve with one of the high-capacity switching chips from National (LM3409HV for instance).

[RCBrooke]

On the 24 volt power supplies, how are you protecting them from salt water drips, splashes etc.? I've been wondering if a meanwell set for constant voltage might make a good option (from a safety point of view not dollars) for driving the CAT4101 boards.

[bluebayou]

For 144 LEDs you'd need 24 CAT4101 circuits. No one's putting a single CAT4101 on a board (that I know of). For instance, my design uses 3 of them per PCB, so you'd need only 8 boards. If you stick with LEDs that are on the lower-end of the Vf spectrum, which should be easy-ish to do, you can probably sneak 7 LEDs on each CAT4101 (sum of Vf basically needs to be 24.5 or lower). In that case, you'd need 21 circuits, or 7 3-up boards.

Regarding power supplies, FishMan is about right - you need to budget your LED current plus about 20 - 30 percent. If you target 700mA drive current, you're talking about needing roughly 20A. You'll likely end up with multiple supplies as one single supply that large will be hard to find and/or insanely expensive. You need to decide if you care about power factor correction, as well.

I agree with FishMan on cost as well. The HLG drivers are very good in terms of cost per watt of output, so they're hard to beat in that respect on a large tank. If you go with HLG drivers, the biggest "issue" will be dealing with parallel strings and the fact that you'll only have a few discrete groups of LEDs for dimming. If you go with the CAT4101 design, you'll have much greater resolution for control (smaller groups of LEDs) and won't have to deal with parallel strings, but you WILL have to deal with having lots more "things" involved with driving your LEDs. It's a tradeoff based on your preferences, I don't think there's a clear one size fits all answer.

Back a few posts I was pondering the concept of trying to generate a DIY design that was equivalent to an HLG. I think this would be easy to achieve with one of the high-capacity switching chips from National (LM3409HV for instance).

I did mean circuits, I know there are 3 to each physical board. I'm thinking the same in regards to the HLG's only giving me 2 or 3 large groups of resolution instead of 24 smaller groups. I think I will probably go with the 4101's for many reasons not the least of which is to learn more about EE. Some of the benefits that I can think of for having the greater resolution would be:

Nightlight
Cloud Effects
Color change via ratio's of RB and CW as well as dimming/

I would love to try to come up with a LM3409 solution but know that I simply don't have the background necessary yet. Has anyone tried to create a system that has each LED independently adjustable?

Re: my independent slot mounting setup: What do you think of this idea? One issue I've thought of is that the heatsink is 28mm and the star is 20mm leaving me with ~4mm on either side as a lip to set inside the channel. The most obvious concern with this is shorting, the connections are millimeters away from aluminum channel. Not a good thing. I've thought about a connector solution but don't know enough about what is available to know if this is feasible.

[der_wille_zur_macht]

On the 24 volt power supplies, how are you protecting them from salt water drips, splashes etc.? I've been wondering if a meanwell set for constant voltage might make a good option (from a safety point of view not dollars) for driving the CAT4101 boards.

I'm protecting mine by keeping them AWAY from water! :) On tanks where it's not feasible to literally locate them far away from water, I put them in a large box or cabinet with ventilation, or provide obvious and foolproof shielding from wet areas. You certainly don't want the power supplies OR the driver boards getting wet. You COULD use a sealed power supply, but you've got to protect the CAT4101 boards themselves as well...

I would love to try to come up with a LM3409 solution but know that I simply don't have the background necessary yet.

User theatrus came up with a driver based on the LM3404 a few pages back. The 3409 is similar but has more capacity, iirc. I started playing with it in Eagle a few days ago but don't think I am going to pursue the design at all - I have too much else going on and no immediate need for a driver that "large" and I don't have enough LEDs laying around to test one anyways!

Has anyone tried to create a system that has each LED independently adjustable?

This would not be challenging but it would be expensive in many ways. Firstly, you'd be building/buying circuitry for EACH LED instead of for a group of LEDs. Secondly, regardless of if you're using a switching or a linear driver, there's pretty much always a static efficiency loss per driver circuit. If you have a driver that's 90% efficient with 6 LEDs, you may only hit 70% efficiency designing with the same IC for one LED. So you're spending a lot more up front, AND taking an efficiency hit which translates into dollars lost longterm as well.

Re: my independent slot mounting setup: What do you think of this idea?

I think it sounds interesting but I don't know if I'm following your description well enough to critique it. One comment though - typically I like to experiment flexibly then design solidly. By that I mean that I build experimental builds to be flexible in as many ways as possible - repositioning LEDs, changing their height and angle, and so on. Then when I build something "final" that I want longterm, I often find it's simpler and cheaper to design in a fixed format, instead of designing with the same level of flexibility. It's hard to get flexibility, low cost, and long term reliability at the same time, IMHO. You want the flexibility when experimenting so you can determine what you want, but then once you know what you want, you don't need the same flexibility. Just something to think about.

[RCBrooke]

Thanks For the reply, yup don't mix water and electricity - Check, been there done that.

I was planning to mount the CAT4101 boards in one of the aluminium boxes attached/near the heat sinks, so unless I drop the whole thing in the water I should be OK (It only happened once I swear!

I was under the impression the, oh say potrans (sp?) needed to be left out of a box - that is to say well ventilated. Unfortunately I'm going to have to keep the power supply in the 24" space I left behind the tank so I was thinking I might be best served using one the water resistant meanwells (IP67 ?) to run for example 2 meanwells each 21.5v at 2.1a for the 6 CAT4101's (6 LED's each).

Thought I'd run it by ya'll to see if there's aspect I overlooked. I think to get a quick start, I'll use 3 ELN-60-48D's and convert to the CAT4101's after I can get the parts/boards.

[TheFishMan65]

IMHO the CAT4101 can't be placed in a box. Maybe it is just my design, but they get very warm.

[RCBrooke]

In Eagle is there a way to turn on visible rule / measurements. For example If I wanted to change the CAT4101 board to something other the 2"x2".

This probably should be posted as a separate post but I was looking at the CAT4101 board. Great job and thanks for all the help you give!

[RCBrooke]

Good thing I asked. Fishman65 how did you mount / place yours?

[der_wille_zur_macht]

You can turn on a grid of dots or lines. Click the little icon in the upper left that shows dots in a grid and you can specify a main grid and a secondary grid, as well as toggle the dots or lines on or off.

That said, that's only going to give you a visual representation of the grid, which is active even when it's not visible. Secondly, you can click the info tool (the little i) and then click on any object and view or edit it's position relative to the origin. So, for instance, you could click on the board outline and change it's position that way, instead of using the move tool and lining up with a grid.

It's also worth noting that if you're changing the board outline to a larger size, you'll probably want to move other components, make the ground layers larger, and so on...

[RCBrooke]

Smacking self upside of head. The info button of course! I used it to reposition the via's, don't know why it didn't occur to me to use it for the board's size. Eagle takes some getting used to! kept giving me "can't back annotate" error until if figured out it was trying to use the wrong tool.

Switched to a double CAT4101 and added a LM317 & pot to hit that +0.5v sweet spot with mix LED's better (thinking of the soon to be out XM-L's with XP-E's). Mostly just practice - I used spice (p_spice?) about 20 years ago.

Thanks.

[TheFishMan65]

I will be mounting mt driver with the LEDs about 2 feet above the tank. I hope this is above the 'splash zone' as I am planning no special protections. They are mounted such that I have good convection current and I am hoping that will be enough.

[RCBrooke]

I thought 2' up sounded like the perfect distance as well, with 40 deg optics.

I had thought to mount a aluminium box to the heat sink with the drivers inside, along the lines of soundwave's (around post 295) only two independent from each other (no L channel frame). As for the heat from the CAT4101's, I wonder if C-channel thermal epoxied across the chips then to the housing could be arranged so as to provide a heat sink for the CAT4101's.

I was also thinking of buying the tank mount stand for the Ecoxotic Panorama but read a review that that the upper arms come with the light fixture not the stand.

Well off to work!

[DustinB]

I haven't seen a need for a heatsink on the drivers at 700mA. I have mine in a small currentusa t5 fixture with my led heatsink. I have 2 fans blowing through the fixture and that is plenty to keep the drivers fairly cool.

[TheFishMan65]

RC L channel would help. I had some extra material from my build (check my album) and it did wonders. Remember anything you can do to keep the electronics cool will make them last longer.

[der_wille_zur_macht]

Switched to a double CAT4101 and added a LM317 & pot to hit that +0.5v sweet spot with mix LED's better (thinking of the soon to be out XM-L's with XP-E's). Mostly just practice - I used spice (p_spice?) about 20 years ago.

Thanks.

You're probably well aware of this but putting an LM317 in front of a CAT4101 is just transferring load from one linear to another - you're going to be taking an efficiency hit either way, the only advantage is dissipating heat from two packages instead of one. Also the LM317 has a pretty big minimum dropout specification, so in order to run a circuit with one of them inline you're going to need a big overall voltage drop anyways which means a pretty big efficiency hit (At 50c and 1A the minimum dropout is something like 2v). You're probably going to be near the thermal limit of the LM317 in order to meet it's minimum voltage drop at the current you'll be running your LEDs at.

If you want to be able to run a bunch of CAT4101's at different voltages off the same power supply and don't care about the efficiency hit of dissipating the extra power in a linear device, you might as well just experimentally determine an appropriate value of power resistor and put that inline with the circuit. That way you're able to get the exact voltage drop you need, instead of having to hit a minimum drop in the LM317. This approach is actually what's recommended in the CAT4101 datasheet for voltage drops greater than what the IC can handle.

Of course another option is to just get multiple DC power supplies and "dedicate" a supply to each Vf you need.

Regarding heatsinks and mounting the driver boards - I haven't had to put a heatsink on one yet, but most of mine are running at low dropouts and all of them are essentially in free air (the most "constrained" I've had one is in a 2' x 1' x 1' plywood box with a large vent in the top.) If I were to mount one in an enclosed space I would absolutely provide some air movement and/or heatsinks. The good news is you can determine this experimentally. Build your setup, and run it, and see if they get hot enough to trip the thermal protection feature. If they do, add more air movement and/or heatsinking. If they don't, you're good to go.

[TheFishMan65]

dwzm, Can you leave your hand on it? IIRC I could barely leave my finger on the CAT4101. I ran for a couple hours and never hit the thermal protection.

[der_wille_zur_macht]

I can touch all of mine and not get burned. Those that have higher drops are not comfortable to touch for more than a few seconds. I know this is highly subjective but I'm guessing this indicates it is well below the maximum junction temperature of 150c.

[TheFishMan65]

"not comfortable to touch for more than a few seconds" that is what I am remembering. I think when I tested one I did not have a problem. When I ran several with different Vf from the LEDs is when I noticed the heat. Since heat is the killer of electronics I would recommend some sort of cooling, but I also agree that we are probably below the 150C point.

[DustinB]

Have you guys adjusted your power supplies til you just get the 700mA or so(based on whatever your RSET resistor is)? When doing this I can hold my finger on the drivers indefinitely with the fans blowing through the fixture. It's pretty warm, but not to the point of having to remove my finger.

I'm running my LEDs all at 700mA with 6 per string on each driver FYI...

[TheFishMan65]

How many strings? What is the voltage of the power supply and the voltage of each string, please and thank you.

[der_wille_zur_macht]

Yeah, pretty much Dustin. It's kind of a six-of-one situation. You can EITHER adjust the Vin upwards until you see the target current on your LED string, OR adjust Vin upwards until you see the drop across the CAT4101 start to increase (it'll stick at .5v when you're below this point). These two events should happen at the same time, and at that very point, the chip will be regulating in a true constant current mode with the lowest possible drop. At this point the IC will be dissipating the smallest possible amount of power and will be as cool as possible given your drive current.

[kcress]

Barely touchable(metal) is about 108F, painful is about 110F, which is well below the typical 158F limit.

[artemm]

I am sorry, but i just can't read all 53 page. just cannot. i tried and i miserably failed :(
Maybe it was somewhere along these pages?

Why not do the following:
1) Power supply - buy a well build 100-150W notebook power supply or convert a more
powerful ATX power supply to be a standalone ps.
2) Make strings of leds. For example, for 12V and leds with 4V Vf the strings will have 3 leds.
3) For each stings put a MOSFET with ultra low resistance (there are plenty cheap ones on ebay)
4) Connects gates of all mosfets all together and route to a PWM output or your preferred MCU (powered by a separate voltage regulator)

Positives: no hassle with power supply, no led drivers in common sense, very cheap
schematic, high efficacy (no wasted current on heating extra components like Rs), no
Rs for strings because V fall 100% on the leds.

Negatives: any?

I did not do it for aquarium, but i did it for fun lights with this summer for my wedding :) It works :)
http://www.youtube.com/watch?v=xZQBRB3fuP0
Since i powered the whole thing with 3.3V li-ion battery i could put only one high power led there (in the video it is the white led) and many piranha leds (greens) - it works w/o any problems.

[der_wille_zur_macht]

Negatives: any?


I can think of one major and obvious negative. You're not actually regulating or limiting the current through the LED! You're driving it in a highly imprecise and unstable manner. When the MOSFET is on, the LED is exposed to the power supply with nothing to limit the current. Because of the unnatural V/I relationship of the LED, it basically looks like a dead short to the power supply, which is trying to regulate output voltage, NOT output current. Hence current can and will vary significantly, and if you try to provide enough current to light the LED near it's limits, you will get a runaway situation and something will break.

This might work if you're targeting a very low current and don't care about precision, intensity, or lifetime of the LED, but in a fishtank, I care about ALL of those things.

A better solution would be to put a current limiting resistor inline with the LEDs in addition to the MOSTFET. Then you'd have control over the current, but it would be static control - if things changed temperature, or your LEDs' Vf was different than you expected when you calculated the resistor's value, your current wouldn't be what you thought it was.

[der_wille_zur_macht]

Since i powered the whole thing with 3.3V li-ion battery

Keep in mind that a li-ion battery will respond very differently from a DC power supply. The internal resistance of the battery effectively acts like a current limiting resistor. Try to run the same LED on a 3.3v DC wall wart and you may blow the LED and/or pop the wall wart.

[RCBrooke]

I was thinking that the per board voltage adjust would be a good thing but the point about just transferring the load from one device to another makes sense. No point in extra components.

Another point you could clear up for me DWZM if you would, on your design the three caps (C4, C5, C6) are all tied to the 24v trace which then goes to each of the L1+, L2+, L3+ headers, are all three necessary or a product of replicating the schematic? (also the C1, C2, C3 on the 5v line). Are they there for ripple?

Thanks much - you guys rock.

[der_wille_zur_macht]

The CAT4101 datasheet specifies a capacitor across the LED string. Of course, the datasheet doesn't go into details about putting multiple such drivers on the same DC supply, much less on the same PCB, so I extrapolated a bit and put one such capacitor on each LED string. I'm sure they could be combined since they're essentially in parallel across 24v and GND but I don't know enough about the properties of capacitors to know exactly how to go about doing that (i.e. I don't know if it would be as straightforward as using a single 3uF cap instead of three 1uF caps).

[SpacedCowboy]

I am sorry, but i just can't read all 53 page. just cannot. i tried and i miserably failed :(
Maybe it was somewhere along these pages?


It may have been useful to read the first page, however... I don't see any current limiting in the circuit you describe, and that'll cause problems. The whole point of the driver chip is to control the current, otherwise we might as well link the LEDs directly to the PSU...

Simon

[der_wille_zur_macht]

I was thinking that the per board voltage adjust would be a good thing but the point about just transferring the load from one device to another makes sense. No point in extra components.


The most efficient way to do that would be to put a switching regulator on the board. But at that point, you might as well run the switcher in a constant current mode and do away with the CAT4101!

[SpacedCowboy]

The CAT4101 datasheet specifies a capacitor across the LED string. Of course, the datasheet doesn't go into details about putting multiple such drivers on the same DC supply, much less on the same PCB, so I extrapolated a bit and put one such capacitor on each LED string. I'm sure they could be combined since they're essentially in parallel across 24v and GND but I don't know enough about the properties of capacitors to know exactly how to go about doing that (i.e. I don't know if it would be as straightforward as using a single 3uF cap instead of three 1uF caps).

I'm reasonably confident that the 1uF cap is just there to help the PSU cope. I've not had any problems running without any (equivalent, because it's in my own circuit), when using a well-regulated PSU.

The caps on the input 5v line are needed "in noisy environments", and I would guess are just there for decoupling purposes. It's pretty standard practice to decouple Vin on digital electronics. I'd keep them because I'd reckon there's enough digital noise going on that there's no harm in having them.

Simon.

[RCBrooke]

SpacedCowboy, just for curiosity's sake, if the caps on the 24v line were to be changed, does it stay at 1uF or does its value change?

Thank you.

[SpacedCowboy]

SpacedCowboy, just for curiosity's sake, if the caps on the 24v line were to be changed, does it stay at 1uF or does its value change?

Thank you.

I'm not sure I understand the question... If it changes, then it obviously has to change [grin]

If you mean, can you replace them with a single 3uF cap as DWZM posited, I don't think it's too critical - a regulated PSU will already have that capacitor on its output, sized according to the PSU. Use any combination (1x3uF, 3x1uF, 1x1uF or none) IMHO :)

Simon

[SpacedCowboy]

Is it my imagination, or has this thread just gone sticky ? If so, congrats to DWZM :)

Simon

[Dejavu]

Congrats on being voted December's Thread of the Month:celeb3::celeb2::celeb1:

[Misled]

Top of the Hill!!!! Congrats DWIZUM!!!!! :thumbsup:

[TheFishMan65]

Congrats!!

I did the combined capacitor. One large one I think it was 10-25uF on the 34V.

[artemm]

yes, i guess you are all 100% right about current limits. With li-ion the battery was the limiter actually. I completelly overlooked it.

So, i am gone for a while to find out how to build a very small and cheep active current limiter.

[sailfish]

Congrats DWZM on Thread of the Month!!

Parts are on order to build one of these and I was able to find a board from a nice chap here on RC. Will keep you posted as to the progress.

[der_wille_zur_macht]

So, i am gone for a while to find out how to build a very small and cheep active current limiter.

You might want to read this thread:

http://reefcentral.com/forums/showthread.php?t=1759758

:D (I kid, I kid!)

[chrisfowler99]

Ooh...sticky...congrats!

[TheFishMan65]

DWZM endless loops can get you into real trouble if there is not a way out :)

[bluebayou]

Congrats DWZM! and thanks so much for all your help and time.

[imagex]

Another question guys... ok on a powersupply with 24v 6.5a how many 3 boards can i run?? and also is it 1a per cat4101 or is it configured on the pcb to run 1a per board? or actually 700ma as the way it's configured.. cause usually it's .7a per string correct? so each cat4101 need .7a or is it the .7a to the pcb with 3 cat4101? cause i'm trying to run a array with 6 maxed out boards would a 6.5a be sufficient?

[S&KGray]

Another question guys... ok on a powersupply with 24v 6.5a how many 3 boards can i run?? and also is it 1a per cat4101 or is it configured on the pcb to run 1a per board? or actually 700ma as the way it's configured.. cause usually it's .7a per string correct? so each cat4101 need .7a or is it the .7a to the pcb with 3 cat4101? cause i'm trying to run a array with 6 maxed out boards would a 6.5a be sufficient?

The rated max of the CAT4101 is 1A, but I think at least 1 person has pushed it a little above that. The LED current is set by the value of the Rset resistor; there is a table on page 7 of the CAT4101 datasheet that lists values for Rset and the corresponding LED current. Most people are using an Rset of 768 ohms for 700mA LED current; an Rset of 549 ohms will give you 1A LED current.

The current is per CAT4101 so total current per board would be x3.

I believe it is recommended to choose a power supply so that you are using up to 80% of its max amperage. So for a 6.5A power supply, you should try not to use over 5.2A.

For 6 boards at 1A per string you would be using 3A per board, total of 18A. You would need a power supply that puts out about 22A.

For 6 boards at 900mA per string you would be using 2.7A per board, total of 16.2A . You would need a power supply that puts out about 20A or you could use 3 of the 6.5A supplies (each one driving 2 boards). You would be using 5.4A out of 6.5A or 83%, but that should be okay.

Anyone feel free to chime in if I am giving the wrong info. ;)

[der_wille_zur_macht]

That's perfectly correct and I agree with your assessment that you'd want three of the common 6.5A supplies to run six 3-up boards at 1A.

[imagex]

so basically 2 per 6.5a power supply correct?? but thats at a 1a perspective if at .7a then i could run 3 x 3up boards right?? wowsers well was thinking it was per board well that puts a whole different view on this project..

[twinreef]

2.1 * 3 = 6.3 that will be over the 80% of its max amperage.

[kcress]

Don't get toooOOOOoooOO hung up on the, "don't fully load your power supply", rule. 80% is a guide line. 82,,85 isn't going to cause a big problem. 80% would typically be good efficiency and not going to thermally put one on the edge. 90% would be too little room for comfort though. As you crowd the 80% line cooling needs to be thought about. Make sure your design allows ample air flow through and around the supply.

[jrsaindo]

the pwm signal on these drivers would only be a 5v correct?? so if i took a 7805 off the powersupply and run it to a 555 then run it into the pot then the drivers then it would work fine?

The PWM in the spec sheet states that the logic high and low levels are 1.30V and .40V respectively.

[TheFishMan65]

No it says that the low maximum value (guaranted off) is 0.4 volts and the minimum high level (guaranted on) is 1.3 volts. So between 0.4 ad 1.3 we do not know how it will behave.

[RCBrooke]

The 0.4v - 1.3v range, I'm not sure if it applies here but is it the same phenomenon the causes the step drop off that was talked about on the meanwell dimming? Maybe it was steep cut-off? Oh well, hopefully you guys know what I'm asking even if I said it badly.

Randy

[TheFishMan65]

PWM is either on or off. There is no dimming by lowering the voltage or current. It gets full current and voltage (as set with the resistor) on and off many times per second. To our eye it looks like it dims. The amount of on time to off it was causes the brightness changes.

The 0.4 is the highest voltage allowed to guarantee the LEDS will be off. The 1.3 lis the lowest voltage to guarantee they will be on. If the voltage was one volt on the PWM I am guessing some CATs would consider that on and some off.

So Randy nope different phenomenon on the meanwells.

[RCBrooke]

Thanks! Always great info here.

[terahz]

I've noticed on my CAT4101s that they are quite unstable based on their input voltage. Nothing like the datasheet shows. Basically I can get about 20%-30% increase in PAR by varying from 21V to 24V on the potrans 6.5V PSU. That's on both blues (XP-E) and whites(XP-G); 6 leds each driver. I'll try to measure the actual current one of these days, but just wanted to point it out. Has anyone seen similar results?

[DustinB]

So you are actually getting an increase in PAR by burning off more extra voltage as heat?

[TheFishMan65]

What was the voltage on a string? I am guessing 20.5, But if 21V is not enough voltage to get the current set by the sense resistor that could be part of the problem. Also IIRC I tried to adjust the power supply up until the output voltage stayed the same. It never happened. Instead the voltage started to change slower. I am not sure it would have been 20-30% but we know our eyes can't tell that change easily. So I would say that I saw the same thing.

[terahz]

So you are actually getting an increase in PAR by burning off more extra voltage as heat?
That would be the case if the driver was actually doing what it should, but I don't think that's the entire story. The heat does increase but also does the output of the LEDs so my guess is the current also increases.

What was the voltage on a string? I am guessing 20.5, But if 21V is not enough voltage to get the current set by the sense resistor that could be part of the problem. Also IIRC I tried to adjust the power supply up until the output voltage stayed the same. It never happened. Instead the voltage started to change slower. I am not sure it would have been 20-30% but we know our eyes can't tell that change easily. So I would say that I saw the same thing.

~V18.6 on the whites and ~V19.5 on the blues. I have the whites on V22.5 and the blues on V24. On all strings I can see difference in brightness by moving from the current value to within +.5 of the string. Just checking that I'm not the only one with this result :)

[OTCHU]

after some tests of my 1/3 build ......
so my module have 5 strings of 6leds ... here are the numbers:
all the cat4101 are set up for 700mA
Power supply:21.5V

string 1: between Cool White XRE Leds: 20.4V Current: 690mA
string 2: between Cool White XRE Leds: 19.3V Current: 690mA
string 3: between Cool White and Royal Blue XRE Leds: 19.9V Current: 660mA
string 4: between Blue Royal XRE Leds: 20V Current: 690mA
string 5: between Blue Royal XRE Leds: 20.4V Current: 680mA

What you guys think about that ?
Little concern about the string 3. Did check the resistor for the current and it's ok. Did change the string ... still have the same current. I will change the cat4101 tomorrow to see if it's a default one. Somebody had this problem before ?

Thank you
Vincent

[OTCHU]

terahz ... I did see that too when you increase the Voltage of the power supply ... I have the number with 21.5V ... will do the same tonight or tomorrow with 24V

[OTCHU]

ok did the test ... looks like the the cat4101 need more than 0.5V !! between 0.5V and 0.8V the current still going up. At 0.5V I was only at 550mA (set up for 700mA). And when I got the 0.8V, I was at 700mA

I did the test until 24V of the power supply so 3V in the CAT. Between 0.8V and 3V, nothing change ... just a lot of heat !! lol

So conclusion, we should go at 0.8V to have the 100% efficient from the CAT. Somebody saw that too ?

[SpacedCowboy]

ok did the test ... looks like the the cat4101 need more than 0.5V !! between 0.5V and 0.8V the current still going up. At 0.5V I was only at 550mA (set up for 700mA). And when I got the 0.8V, I was at 700mA

I did the test until 24V of the power supply so 3V in the CAT. Between 0.8V and 3V, nothing change ... just a lot of heat !! lol

So conclusion, we should go at 0.8V to have the 100% efficient from the CAT. Somebody saw that too ?

My suspicion is that this has more to do with the variation in LEDs than in the CAT4101... From what we've seen, the LEDs can vary quite significantly...

Simon

[TheFishMan65]

I agree with Simon - large LED variation. Otchu I would not worry about string 5. IIRC the circuit has a 10% variation. If anything I would worry about string 2 - with the low voltage the CAT may get kind of hot.

Sorry I did not get a change to meause mine tonight.

[der_wille_zur_macht]

Different subject but ST just released a demoboard for showcasing one of their microcontrollers as a LED driver. It's a buck design with 4 channels on the board, each capable of 10 HP LEDs (so, 40 LEDs per board). It's $85 at Mouser. The part number is STEVAL-ILL031V1. This is about twice the cost per LED as our DIY design but might be worth playing with or reverse engineering for those looking for a "larger" capacity design.

[OTCHU]

Did more test today ....
I did upgrade the current on the leds at 800mA
When I was at 0.6V internal CAT, my current was at 670mA. I had to go to 1.2V to have my 800mA. Voltage on the 6leds: 21V and power supply at 22.2V ... To be honest don't understand ... the datasheet is telling us to have 0.5V minimum .... somebody have an idea ?

[SkiFletch]

It took me multiple days, but I finally read through this whole thread and my brain hurts :lol:. Now that I know that it's both possible and affordable to DIY LED drivers, I guess I have to decide on how many LED's I actually want to drive, colors, current, optics, but I assume that's all different threads. Perhaps I should close Pandora's box before I get sucked in permanently ;)

[TheFishMan65]

Probably should close the box:). Here is the thread you want:DIY LEDs - The write-up (http://www.reefcentral.com/forums/showthread.php?t=1678127&page=225) Only 225 more pages to read.

Or you could cheat and go to the bottom of page 200 and read the 3 post summary. Most basic questions are answered there.

[Fish'InMN]

Please start referencing the post number, 4994 (http://www.reefcentral.com/forums/showpost.php?p=17783831&postcount=4994), NOT the page number. Pages are meaningless when each individual has an option to change the number of posts on an individual page.

[seti007]

Hi everyone, I have the CAT4101 boards on order. I am currently trying to fugure out the best way to turn the LEDS on and off using my AC Jr. I am not using PWM but rather using a 10K pot on Rset to dim the leds. After the initial adjustment to get the color right, i plan on not messing with the POT too much. Right now Im thinking about being able to turn all the BLue LEDs and all the White LEDs on 2 seperate outlets controlled by my AC jr. In order to turn on the blue for example, I would connect a 5V wallwart to the PWM and Vin pins I woulld therefore turn the walwart on or off using the AC jr. Same thing goes for the White LEDs I would also have a 24 volt 13 A Mean well power supply on a timer, designed to turn on before the LEDs are turned on.
Would that scheme work to turn the lights on and off? is there a better way of dong this?
A secong question is, how many cat4101s can one wallwart handle? do I need a current limiting resistor before I connect it to the PWM and Vin ports? can these two ports be connected to the same 5v walwart?
TIA

[TheFishMan65]

Fish'InMn, but that post only gives a third of the information. I don't have time to go back and get links each time I refer to it. I can try and start remembering to add at 25 posts per page. Got a better idea?

seti, As long as EACH CAT4101 HAS ITS OWN POT you maybe ok, but keep the leads really short.
Your powering scheme should be OK. I posted somewhere and IIRC you cna have either the 5 v or 24 v come on first.
CATs probably draw a few milliamps (let's overshoot and say 25). A 500 ma supply woulld run 20. Vin and PWM can be connected to the same supply at least that is what I did.

[DustinB]

One big factor to take note of when using your wall wart with the VIN, you have to keep in mind that the majority of wall warts only output their rated voltage at their rated current draw. This could mean that a 5v wall wart could push upwards of 8v or so with a tiny load on it. IIRC VIN has a max of 6v.

[tlittle]

I have followed this thread as far as my headache would allow.....It sounds great...a cheap LED controller.....I am sorry if this has been asked before....can you give me an accurate up to date list of all parts needed and a step by step of assembly....and software download...to produce a good controller......sorry agian, I have gotten a headache trying to follow this thread......

[Fish'InMN]

Fish'InMn, but that post only gives a third of the information. I don't have time to go back and get links each time I refer to it. I can try and start remembering to add at 25 posts per page. Got a better idea?

http://www.reefcentral.com/forums/showthread.php?p=17783831#post17783831

If you don't have time to get the link every time you reference it, then just say post 4994 instead of an arbitrary page number. Are you complaining about remember a four digit number rather than a three digit number?

[TheFishMan65]

I will try and remember 4994 rather than 200. Is there a trick to linking to a post on the page? I looked at but ondering if I have just missed a short cut. Thanks?

[twinreef]

Just click on the post number, then copy and past the link. But that only shows that post not the thread.

[TheFishMan65]

Yes I knew that, but his link got back to the thread. So they can read the other 2 parts of the summary.

[S&KGray]

When you view the single post only link, there is another link on the top right hand corner that links to the thread but starting at that post.

[seti007]

Thanks Fisnman and Dustin, I will keep that in mind. Another question i has was combinibg grounds. The negative of the 24 v and 5v supplies will be connected to ground right? Do yu guys recomment a certain 5v supply that does not go over 5v at load.
Thanks

[der_wille_zur_macht]

There are billions of 5v supplies, use anything you want really. Many of us are using these in conjunction with an Arduino or other DIY controller so we're tying into the 5v and GND from that. But really, anything will work - look for the word "regulated' in the supply's name or description and you can assume it will be OK but it's worth testing anyways.

Regarding the ground connections - yes, you want the negative (aka ground) connection from both DC supplies connected to the "GND" terminal on the driver board.

[Tbduval]

Different subject but ST just released a demoboard for showcasing one of their microcontrollers as a LED driver. It's a buck design with 4 channels on the board, each capable of 10 HP LEDs (so, 40 LEDs per board). It's $85 at Mouser. The part number is STEVAL-ILL031V1. This is about twice the cost per LED as our DIY design but might be worth playing with or reverse engineering for those looking for a "larger" capacity design.

Thanks DWZM! Now I might actually have to read this thread. I was trying to avoid the trap but it does not look like it now!

[artemm]

So, i am back to tell my driver story. The beginning of it, actually.

I actually have read the thread from page 1 to the last one this time. It took a week :) I also have read all the datasheets mentioned here.

So, some time ago i asked why now use a simple scheme with PWM control and w/o current limiter because i used it before and it was fine.

Then i realized that in my application the current limiter was the battery i used, it simply cannot give more. So, for power supply application i NEED to make a current limiter.

I started to plan one (schematics and proteus simulation). Tried a simple one but it dissipated way too much power. So, i started to build a switching one. When i added the comparator i realized that i am building a chip from discrete components and i was still to add overcurrent protection and pwm control. Also, the efficiency was not very good. So, i stopped being silly and went to choose a good driver chip. :)

Now for the chip selection.

Here is the list of all mentioned drivers here:

CAT4101 - linear regulator
STCS1 - linear regulator
NCP3066 - 1.5A switching regulator, buck or boost (but not buck-boost), 250kHZ osc
ZXLD1366 - 1A, 60V buck
MBI6651 - 1A, 36V, buck
MIC3203 - 1A, 42V, buck


The problem is that i don't like all of them. Here is why:

Linear regulators are simple out of question. They need power supply very carefully matched to the Vf of the leds at certain current. Which is BTW fluctuates as it wants and is different for all led types. If, i will decide to increase or decrease current in the future, add or remove some leds i will need a new power supply. Also, i will need either match leds to the PS or buy a PS that can be regulator. If you look as such supplies you will see that they are pretty much never water protected and this is a no-go near a watter filled glass container. Best PS to use. i think, is a factory made notebook style one. It is pretty well protected from water, not very expensive, has high efficiency and high power output. So, no linears for me.

Now let's look at the BUCKs only. How much voltage i will need to provide to a driver if i want to driver at least 8 leds string? Aprrox 3.5x8=28V. What about 12 leds? Thats around 42V. Actually a few volts more than that in both cases. These are non standard voltages and i will need to buy not so popular power supply for it. Also, if i add more leds i might run into a problem in the future. Power supply issues are the same as for linears. I am not saying this is bad or anything, but it just does not feel comfortable for me.

The only boost here is NCP3066. The problem with NCP3066 is that i don't know how much boost it can give. How high can it go? With what efficiency? It has only 250Khz freq, so, for high boost it will need pretty big inductorl. Also, i don't like boost alone either, because then i am tied to a number of leds and ps voltage too because summ of Vf on leds MUST be higher than
PS voltage. Not versatile either.

So, the only option for me (me and only me, am not saying that everything else is bad) is a buck-boost configuration. And then i found this.

BEHOLD!

LTC3783 from LINEAR TECHNOLOGY

It does boost up to 54V, can be configured to use only one inductor in SEPIC configuration used external MOSFET to driver leds. The switching freq is up to 1MHZ + tons of neat features.

Has a good design examples in Design not 406 (dn406f.pdf - google will help)
It is very well documented in the PDF datasheet with examples and calculations.

Yes, it is not easy to solder (TSSOP package) and need tons of external components. But the components are dime a dozen and one such driver can drive at least 12 leds and i believe actually more.
For boost it can give 95% efficiency, for buck-boost 93%. Using such driver in buck-boost configuration i can choose any PS and then put any number of leds, even one just to see if the thing work (though the number of leds
will affect efficiency, so i need to calc everything to maximize efficiency for a prospected number of leds).

What do you think?

DATASHEET: http://cds.linear.com/docs/Datasheet/3783fb.pdf
APP NOTE: http://cds.linear.com/docs/Design%20Note/dn406f.pdf


Also, i looked at the CREE leds specs and i am lost why everyone drives them at 500-700mA? They are best driven at 1A and live long at that current.

[der_wille_zur_macht]

BEHOLD!

LTC3783 from LINEAR TECHNOLOGY

...

What do you think?

It looks like a nice chip. It strikes me as very very similar to the LM340x chips from national, only in a slightly harder to solder package. If I were in your shoes I would definitely check them out before proceeding.

Also, i looked at the CREE leds specs and i am lost why everyone drives them at 500-700mA? They are best driven at 1A and live long at that current.

Efficiency and lifetime differences are significant. Of course, this is a personal choice and some people will value outright intensity more than efficiency or lifetime, but for me, I'm leaning slightly towards efficiency and lifetime, since I can get intensity by simply adding more LEDs. Check the output/current graphs in those datasheets - most of these LEDs will lose 30%+ efficiency going from 500 - 600mA to 1A.

[artemm]

I see your point about current and efficiency. I was thinking about current in terms of lifetime and that is not not really important i think, the lifetime is huge. But efficiency is important, especially when you say 30% is lost. I will have to recalc things.

As for LM340x series:

LM3401 - seems to be buck
LM3402 - buck
LM3404 - buck
LM3405 - buck
LM3406 - buck
LM3407 - buck
LM3410 - boost, SEPIC , but only up to 24V

So, nothing is close to LTC3783 amongst LM340x

[der_wille_zur_macht]

Take another look at those datasheets - I know at least a few of them can be configured in boost, and most or all of them have HV versions that are good to 75v i/o - also, look back a few pages for a design by user theatrus, which iirc uses one of these chips in buck/boost topology.

[terahz]

Linear regulators are simple out of question. They need power supply very carefully matched to the Vf of the leds at certain current.

What is the problem with using the adjustable power supply almost all of us use? (http://www.mpja.com/prodinfo.asp?number=16854+PS) It can be adjusted from ~18V to ~25V. Yes, it is not waterproof, but put it in a plastic container and it will be as much waterproof as a laptop one.

At least that's how I see it.

[artemm]

Take another look at those datasheets - I know at least a few of them can be configured in boost, and most or all of them have HV versions that are good to 75v i/o - also, look back a few pages for a design by user theatrus, which iirc uses one of these chips in buck/boost topology.

heis his quote:
"The efficiency reason and allowing multiple types of LEDs per supply was part of my motivation for the LM3404HV buck converter version."

As i said: LM3404 is a BUCK only regulator.

As for the datasheet. Here are the names of the parts copid from the datasheets (i actually also searched each for the "boost" word -non found in regards to a described driver):


LM3401 - Hysteretic PFET Controller for High Power LED Drive. Had to read the datasheet. It seems like boost only.
http://www.national.com/ds/LM/LM3401.pdf

LM3402 - 0.5A Constant Current Buck Regulator for Driving High Power LEDs
http://www.national.com/ds/LM/LM3402.pdf

LM3404 - 1.0A Constant Current Buck Regulator for Driving High Power LEDs
http://www.national.com/ds/LM/LM3404.pdf

LM3405 - 1.6MHz, 1A Constant Current Buck Regulator for Powering LEDs (can gen Vboost up to 26V)
http://www.national.com/ds/LM/LM3405.pdf

LM3406 - 1.5A Constant Current Buck Regulator for Driving HighPower LEDs
http://www.national.com/ds/LM/LM3406.pdf

LM3407 - pdf of protected, but it is 350mA buck
http://www.national.com/ds/LM/LM3407.pdf

LM3410 - 525kHz/1.6MHz, Constant Current Boost and SEPIC LED Driver with Internal Compensation
http://www.national.com/ds/LM/LM3410.pdf

I actually looked at all high current led drivers from National. The only SEPICS/buck-boosts are in 342x series and they give up yo 32V for boost and have tons and tons of external components.


What is the problem with using the adjustable power supply almost all of us use?

Absolutelly nothing is wrog with them. I am sure they are good power supplies. I just don't like to idea of building everything for a certain voltage, the circuit must be adjusting to PS, not PS to the circuit, that's IMHO. And i don't like building a plastic box and they water seal all the holes in it and between the parts and the think if it will live okay with air flow at all.

[artemm]

I just took a deeper look at LM3423. I was wrong about it. It can boost up to 75V and it has also status pin, which is nice to have and also high speed dimming (up to 50Khz) and the datasheet says it can be dimmed very low, basically it depend of the pwm generator.
If it is all so then LM3423 seems very interesting too. I am lost here, which one to select

http://www.national.com/ds/LM/LM3421.pdf

[kcress]

Also the :
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1094,C1766,P81080

[kcress]

And check Maxim-IC

http://www.maxim-ic.com/datasheet/index.mvp/id/5541

Check also their:
MAX16816.pdf
MAX16818.pdf
MAX16821-MAX16821C.pdf
MAX16831.pdf
MAX16834.pdf

Don't forget the Zetex:
www.diodes.com/datasheets/ZXLD1370.pdf

[artemm]

LT3755 - yes, its very interesting too, open led condition signal here.
http://cds.linear.com/docs/Datasheet/37551fd.pdf

MAX16812 - PWM is only 100:1, 500khz switch. Docs suck.
MAX16816 - tqfn package only, no way i am messing with package at home on a home make (TT) PCB. I CAN do it, but this is just plain wrong and i am not in the mood for schmartboards.
MAX16818 - tqfn only
MAX16821 - tqfn only
MAX16831 - tqfn only
MAX16834 - has sop :) No ENABLE pin, has fault output, datasheet sucks. NO idea how much voltage can it boost safely.

ZXLD1370.pdf - i am lost in their datasheet. What max voltage can it boost to? Look at page 8. No 18V power supply and no more than 8 leds on the graphs. Why? Crazy.
Otherwise it is a good doc. The chip has fault state output info, good pwm resolution at 1KHZ. BUT not internal OVP, so, has to build OVP externally.


Actually, i find LINEAR device more appealing because their datasheet are more detailed, they describe how to select each component, give a lot of examples with real components. They also specify efficiency almost for each example application. I feel more confident with such docs. Big plus for Linear.

So, thus far i have:

LTC3783 - 100% sure it will work.

LT3755 - 100% sure.

LM3421 - pretty sure it will work nicely.

ZXLD1370 - is a nice one, but need to know how much it can boost and what the deal with the graphics on page 9.

All of the are TSOP package variants, so, it is hand solderable at home.

[kcress]

Nice synopsis!

I agree with all your findings.

Maxim data sheets don't suck but sure aren't great.

Almost without exception Linear data sheets are da-bomb.
Of course Linear parts all cost a small fortune. May be that's to pay the documentors.

But! If you want the best in assessment, nothing beats the National Work Bench tool to see if a part will do what you want.

[artemm]

Well, i don't know about the fortune. Nationals LM costs just 3$ less than LINEAR's LT. So, what's the big deal if yhou spend over 200$ on the leds anyway? This is simply in the cost estimation error margin. Now consider that LT3755 can output 75V at 0.7A! That's around 20 leds from one driver at 700mA (for cree xp-g). So, what is cheaper now?

By that tool you mean MULTISIM or something else?

I want to return to a question about LED efficiency at different current.
I look at the XP-G datasheet.
http://www.cree.com/products/pdf/XLampXP-G.pdf
Let's take XPGWHT-L1-0000-00FE4 (neutral white)

at 350mA - 100% of flux, 122lm, Vf=3V, P=1.05W, 116 lm/W, let's count it as 100% eff

at 700mA - around 190% ,232lm, Vf=3.2V, P=2.24W, 104 lm/W , eff 89%

at 1000mA - 250% flux, 305lm, Vf=3.3V, P=3.3W, 92 lm/W, eff 79%

So, it does not seems like 30% loss of efficiency at 1000ma. More like 20%, but that a lot too. 350mA would require too many leds, so, it seems like 700 mA is a good choice.

The interesting thing here is how some fight to gain extra 1-3% of driver efficiency while the led itself goes inefficient by 10%.

What i cannot find is a doc with a graph showing led life vs driving current.
I looked here: http://www.cree.com/products/xlamp_xpg.asp#xrcdocs

[artemm]

I just realized that i totally overlooked the safety issue. And if a boost regulator will boost up to 50V then it can possible give out 33mA through the body if everything is dry. If you are wet it can be a lot worse. 33mA.
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.

So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current :)
And the PS must be sealed and kept above the floor.
What do you think?

[kcress]

I just realized that i totally overlooked the safety issue. And if a boost regulator will boost up to 50V then it can possible give out 33mA through the body if everything is dry. If you are wet it can be a lot worse. 33mA.
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.

So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current :)
And the PS must be sealed and kept above the floor.
What do you think?

1) Yes certainly 50V is a hazard. If you have the heatsink properly grounded and a splash shield there should be minimal hazard.

2) If you short things the controller will drop the voltage to try to get down to the programmed current.

3) Off the floor is definitely better than on the floor.

[artemm]

1) I doubt that there is any point in grounding the heatsink. The transformer in the PS galvanically decouples mains and the LED circuits, so not current will flow to the ground. There is not closed cicuit there, imho.

2) But shorting i meant shorting with your own body. The body R is a lot higher than R of leds, so driver will rise voltage to rise current (like you added
tons of leds :) ) If something just short in a usual way the driver will shutdown automatically and it is no hazard to anyone or anything.

[kcress]

1) I doubt that there is any point in grounding the heatsink. The transformer in the PS galvanically decouples mains and the LED circuits, so not current will flow to the ground. There is not closed cicuit there, imho.



Yes there is still reason to ground the heatsink. You can have capacitive or inductive coupling to the metal. If for whatever reason there is a fault to the heatsink and you are referenced to Earth and the heatsink is physically bonded to EARTH then you can't be shocked by just touching the heatsink. Many switching supplies have leakage inductance that can still get you. Often the switching supply is galvanically isolated only to have it alternately coupled thru the EMI filter network.

[artemm]

Umm. Let's clear this a bit. The switching POWER SUPPLY (220v in my case to 18V) is located far away from the heat sink. About 1 meter away.
What's need the heatsink are the drivers. The drivers hardly can any capacitive coupling, not to mention at such big distance (several cm). Inducative - i don't know, but i don't it can be anything high.
Now, if there a fault to the heatsink (it is very high prob fault actually in such setup) if i touch only the heatsink and nothing else - nothing will happen. No current flow, right?
If i touch the other terminal for leds then the driver will shutdown almost instantly because of OVP.If the heatsink is grounded and and faulted and i touch only the heatsink nothig will happen too. If i touch the other termnial - i'll get shocked anyway and OVP will save my butt.

So, the PS is just too far any coupling. Though, i am not good at this area at all. I'd day i'm very bad at it :) Do you think coupling can happen at such distance from the PS and through all the drivers with high freq controlling?

[kcress]

It doesn't matter what distance you have since the coupling and fault possibilities are all in the power supply.

OVP is not in-any-way there for your safety.

You are right if the heatsink isn't grounded and there is a fault to it and you touch only the heatsink, you won't be shocked. BUT that means you are standing on two drinking glasses or suspended on silk ropes from a dirigible, I doubt this will be the case. Instead you would likely be standing on damp carpet in your bare feet.

If you touch one side of the string and the other side you might get a little shock at 24V -probably more like a discernible tingle. Do it on a 48V string and you would probably experience a painful shock. Shocks of this type are generally not serious, the bigger problem is what happens after the shock. Like how far you fall from the ladder or what your head hits when you recoil...

If you have touchable metal associated in any way with a power cord to a wall outlet, it's simple, you should ground all the various metal parts.

If you want to argue about all sorts of possible scenarios of how you could avoid proper grounding I'm really not interested.

[artemm]

kcress, sorry if it seems that i am arguing. Not, that's not what i am into. I have no problem with grounding any piece of metal around wet areas :) Actually, on another forum i offered to ground it some time ago and some people just laughed at me and that that i am being silly. No explanation followed though. And i cannot explain how it would help either. It is just automatic thing for me since i did all lights in the apartment - i ground everything and then check that the grounding actually works with a resistor connected to mains.

The thing is that i cannot really undertand what's going on in here. As i understand as a protection just from the DC voltage after and before the driver ground will not work. Right? This is the first question.

Next, i understand that the danger comes from coupling in PS. And that's totally out of my grasp of the issue. How much current can go through this coupling? Is there way to test if it is there or not?

[mlsmith]

Different subject but ST just released a demoboard for showcasing one of their microcontrollers as a LED driver. It's a buck design with 4 channels on the board, each capable of 10 HP LEDs (so, 40 LEDs per board). It's $85 at Mouser. The part number is STEVAL-ILL031V1. This is about twice the cost per LED as our DIY design but might be worth playing with or reverse engineering for those looking for a "larger" capacity design.

I own an Aquarium Store and am looking at converting all my T5 lighting on my Live Stock Tanks (currently 48 x 48" & 5 x 72" with more to come) to LED to save on power consumption generated both by powering the ballast and cooling the resulting heat from the ballast and the T5's, plus the cost of replacing the bulbs once a year. You cannot imagine how much power we pull here . Entergy is about to put up a second transformer for us, and is looking at putting in a third phase on our street.
I'm hoping to be able help you guy's with your purchasing and organizing efforts.

Question is, are you guy's interested in my participation since I am a retailer? What I think I can bring to the table, is Organization of the Wiki, and purchasing power.
I'm looking at converting my fish tanks from dual T5 and my Coral/Plant Tanks (HQI & VHO T12) to the equivalent in LED.
I would also like to sell the resulting LED system to other Aquarium Stores, after I iron out all the bugs, which will hopefully enable them to pass on this cost savings to you the consumer.
Additionally, I would like to put kit's together (Finished PCB's & Parts) for the less electronically inclined DIY'ers so that they can benefit from this great project.

Let me know what you guy's think of this.

--Mike

[der_wille_zur_macht]

Mike, I think you need to get in touch with a forum admin or staff member to talk about sponsorship before discussing commercial plans in this forum. Thanks.

[mlsmith]

I would also like to sell the resulting LED system to other Aquarium Stores, after I iron out all the bugs, which will hopefully enable them to pass on this cost savings to you the consumer.
Additionally, I would like to put kit's together (Finished PCB's & Parts) for the less electronically inclined DIY'ers so that they can benefit from this great project.
--Mike

Due to feedback posted here, I would like to redact these lines and offer my apologies. I had no intention of offending RC policy.

Look forward to seeing how this thread progresses.

--Mike

[MaLi]

Greetings,

if anyone has some leftovers, I am interested on two PCBs with the triple driver (DWZM design for CAT 4101). Please PM. Many thanks.

cheers,
MaLi

[neltnerb]

I just realized that i totally overlooked the safety issue. And if a boost regulator will boost up to 50V then it can possible give out 33mA through the body if everything is dry. If you are wet it can be a lot worse. 33mA.
According to this http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
it must be kept under 50mA at all costs for DC, because any higher and you will not be able to let go of the wires. It seems like 50V is too dangerous in the wet area because R of body under bad condition can drop to 100 Ohms
(see http://www.allaboutcircuits.com/vol_1/chpt_3/4.html) that will will pass 0.5A through the body and this can kill you.

So, I think to feed everything from 12-18V PS. 12V is considered safe for wet areas in general.
The use buck-boost driver to feed 12leds per drivers and set overvoltage protection to 42V or something like that. So, if i short on PS side then it is simply safe due to low voltage. If i short after the driver then the driver will try to restore programmed current level and will rise voltage. When voltage will get to 42V OVP will shutdown the driver and release me from the current :)
And the PS must be sealed and kept above the floor.
What do you think?

Please don't kill yourself. Never use electronics that aren't fused and properly grounded! If you don't know how to do that, learn before you hurt yourself!

I have extensive examples of how to safely build LED electronics on my website at http://web.mit.edu/neltnerb/www/artwork/ and http://saikoled.com

They are not intended to deal with water environments, or open LEDs though. You should make absolutely sure that things are grounded so that if high voltage gets into the water, it shorts to ground and blows out a fuse (or even just your wall circuit breaker!) instead of going through your body. For example, grounding the water itself in a salt water fish tank should make it so that if you dropped the high voltage into the tank, it shorts out to earth ground right away.

Best regards,
Brian

[Foxy Brown]

I have some thoughts on this issues people are having here, and the increasing complexity of peoples designs versus other folks DIY skills and willingness to deal with custom PCBs, SMT parts, etc.

I recently had a discussion of the merits of CAT4101 driver on another thread, that can be summed up to "high efficiency and lower heat dissipation because it has lower dropout voltage". The thing is that there are alot of great regulators out there, better than this one by a good bit in fact, but they are limited on input voltage.

Now I'm not totally sure this will work, but I strongly think so. We can run the regulator on the low side of the circuit, having the LEDs feed power into the Vin line. By doing this, the highest voltage seen by a 6-LED string on a 24V supply is about 3 volts, meaning some really great regulators become available to us. This also open up the potential to drive more LEDs from the same driver... For instance 25 LEDs on a 90V supply is only 2.5V at the regulator, so you can use the exact same driver. (Of course this only works for LDO type regulators). I saw someone trying to do this on another thread, and would be super-simple this way.

Can anyone think of a reason this wont work? FYI I just tried it at 24V and it works perfectly... checked voltages at all pins vs ground with the multi-meter too and everything is about right.

Second, I'm not sure everyone is doing this but you should ALWAYS ALWAYS ALWAYS run these regulators in current-controlled mode. This eliminates most of the problems are seeing with variation in LEDs voltages. LEDs are not voltage-based devices, they are current-based.

[neltnerb]

I have some thoughts on this issues people are having here, and the increasing complexity of peoples designs versus other folks DIY skills and willingness to deal with custom PCBs, SMT parts, etc.

I recently had a discussion of the merits of CAT4101 driver on another thread, that can be summed up to "high efficiency and lower heat dissipation because it has lower dropout voltage". The thing is that there are alot of great regulators out there, better than this one by a good bit in fact, but they are limited on input voltage.

Now I'm not totally sure this will work, but I strongly think so. We can run the regulator on the low side of the circuit, having the LEDs feed power into the Vin line. By doing this, the highest voltage seen by a 6-LED string on a 24V supply is about 3 volts, meaning some really great regulators become available to us. This also open up the potential to drive more LEDs from the same driver... For instance 25 LEDs on a 90V supply is only 2.5V at the regulator, so you can use the exact same driver. (Of course this only works for LDO type regulators). I saw someone trying to do this on another thread, and would be super-simple this way.

Can anyone think of a reason this wont work? FYI I just tried it at 24V and it works perfectly... checked voltages at all pins vs ground with the multi-meter too and everything is about right.

Second, I'm not sure everyone is doing this but you should ALWAYS ALWAYS ALWAYS run these regulators in current-controlled mode. This eliminates most of the problems are seeing with variation in LEDs voltages. LEDs are not voltage-based devices, they are current-based.

Hi!

You are absolutely right. If you use an open-drain current sink (there are many of these, and this is the name you should search for to find similar parts), you can connect up an arbitrary number of LEDs in a chain.

The limiting factor on these is mostly in the heat dissipation. The regulator at the bottom is usually linearly regulating whatever voltage is left at the bottom of the chain down to ground at a fairly high current. For example, the 2.5V you suggest at 700mA is producing 1.75W of heat, and that's a fairly benign example.

The biggest problem you will find is that LEDs have fairly wide forward voltage tolerances. So while they might be typically at 3.2V, the *actual* Vf at 700mA might vary from 2.6 to 4.0V! Now, statistically if you had a random sampling and the parts were distributed with a normal function around 3.2V, adding many LEDs would result in a tighter average. However, for any parts you purchase you are likely to see a strong correlation between them because they will be from the same manufacturing line at the same time. So if one LED is 2.9V instead of 3.2V, they are *all* likely to be.

So instead of those errors balancing out, they will compound each other. With a 25 LED chain, that fairly small .3V error in the datasheet means a variation in the total voltage drop of 7.5V. So suddenly, the 2.5V you calculated you'd be dropping at the bottom is *10V* and now you're dissipating 7W from a relatively small SOIC chip.

Even worse, you have to design for the worst case in the *other* direction. If you don't have at least a volt or two at the bottom, you have no regulation capacity, so you have to assume the worst, in which case you're assuming a 4V drop in the design phase, but only a 2.6V drop is actually present! This 1.4V less Vf per LED means you're now dropping *35V* at the bottom, and trying to dissipate almost 25W! That will melt just about any standard chip.

So, the only way to design a system that does this reliably in practice if you are using one of these open-drain linear regulators is to do it completely custom for each system. That way you have measured instead of estimated values for the total Vf. In other words, if you happened to have 35V across that last LED to the regulator, you would just throw on another 12 LEDs, or drop the input voltage.

Another way to help with this is to put in a power resistor at the top of the LED chain to drop the current somewhere other than the main regulator. That spreads out the heat generation beyond the more fragile silicon.

Personally, I highly recommend switching regulators such as the LM3404 and LM3406 for these sorts of high power applications. They will not have any of these problems, but they do have those voltage limits that you won't see otherwise (because they are controlling a power transistor at the top of the chain).

Best,
Brian

[ackerman]

I have a bit of a problem I cant seem to figure out that im hoping someone here might have an idea how to fix. Im running DWZM's cat 4101 triple drivers theyve worked great for the last 6 months but yesterday i noticed one string out of the 3 strings on my blue doesnt shut off when the pmw signal is cut. I switched out the board to my spare board and the problems still there, same string of 6 wont shut off but the other 2 strings still do. Any ideas?

[inky]

I have a bit of a problem I cant seem to figure out that im hoping someone here might have an idea how to fix. Im running DWZM's cat 4101 triple drivers theyve worked great for the last 6 months but yesterday i noticed one string out of the 3 strings on my blue doesnt shut off when the pmw signal is cut. I switched out the board to my spare board and the problems still there, same string of 6 wont shut off but the other 2 strings still do. Any ideas?

Could be a short in the wiring, so PWM from another channel is touching the one that won't go off, or the output wiring is touching......

[ackerman]

All three channels are run off the same pmw signal. I switched one of the strings that was turning off to the channel that wasnt turning off and now that string doesnt turn off, but the string that used to not turn off now turns off on a diff channel of the board if that makes any sense.

[TheFishMan65]

On an unpower boards check that all 3 PWMs are connected and are connected to the incoming PWM signal. Also check if any of them are shorted to ground.

Since it is happening on two boards its sounds like a design or manufacturing fault. Since others are using it I will rule out design. Do you have a blank boards? Check the traces on a bare board and see if they make sense.

[ackerman]

The thing is I can cut the 5v power and the pmw signal completely to the one cat 4101 and the leds still stay lit. Maybe il try replacing 4101 and see if maybe thats the problem.

[TheFishMan65]

How long have you had the 5 volt off for. It could be capacitance. With no PWM (open) mine do not come on when power is applied. So if you apply 24V (or so) to the LEDs, 5 volts on the Vcc power line of the CAT and no signal on PWM it stays on? All three or just the one channel? One board or both?

[der_wille_zur_macht]

This sounds exactly like a fault in the board or a solder bridge. With everything off and the driver board out of circuit, it should be simple to find the fault by probing for continuity.

FWIW, the LEDs should only come on when you have +24v, +5v, and a signal on the PWM pin. Take away any one of those three and they should turn off.

[jeffs86GT]

Hey guys quick question on those who've generated the Gerber files for the Triple CAT 4101 board. I downloaded the CAM file from seeedstudio and then opened the resulting Gerber files in VIEWPLOT and the holes for the 4 Corners and all the VIA openings aren't lined up. Is this normal or could I have done something wrong. Just curious if others tried viewing their generated Gerber files and saw the same thing.

Thanks,
Jeff

[TheFishMan65]

It is not normal. Not familiar ith ViewPlot, but check the orientation center of each level sound like they got corrupted.

[jeffs86GT]

Thanks FishMan I'll take a look at it.

[kcress]

I use ViewPlot all the time and what you see is what you get. So those holes are going to end up where you see them.

[TheFishMan65]

ackerman
Did you ever find the problem. Please share the results. Thanks

[der_wille_zur_macht]

Seed/itead's CAM job has some "issues" with generating the drill file correctly depending on certain conditions on the board. It seems like the drill file gets offset incorrectly, if you have other layers that extend beyond the board dimensions (i.e. a part, such as a connector, that hangs off the edge). So far, it hasn't been a problem - they do a visual check and correct the offset manually. As such I haven't put any effort into solving the problem, since they seem to catch it anyways.

[DustinB]

As DWZM stated, this is normal for seeedstudio/iteadstudio. The offset drill file is from the positive coordinates option on the board. From what I've been able to dig up, it's necessary for the board houses they use. They will manually adjust the files as needed.

NOTE: This cam file is only for use when ordering from seeedstudio/iteadstudio.

[CrazyPuy]

Hello all,

I just finished reading this thread from 3 weeks ago and I'm very interested in this project. I'm a complete lamen when it comes to electronics so would anyone be able to provide me with the GERBER files needed to order through Seeed? I don't have a tank anymore but I wanted to tackle getting back into the hobby one piece at a time.

Thanks for your time!

- Paul

[ackerman]

ackerman
Did you ever find the problem. Please share the results. Thanks

No, been really busy lately and havent had time to test anything yet. Hopefully this weekend il have some time to mess around with it. Ive just been unplugging the powersupply at night so the 1 string turns off.

[jeffs86GT]

Thanks for everyones replies on the Gerber file issue. Good to know and now I can order my boards.

Jeff

[CrazyPuy]

Okay so I was able to find a freeaware version of the eagle program and created the files but what im really wondering is each board really $20.00? I'm trying to go through seeedstudio that is. Thanks all.

[MaLi]

I just received 10 boards from iteadstudio (3x CAT4101) I need only 3 and the rest are for sale. If interested check the Sale section of this reefcentral.

cheers,
MaLi

[jeffs86GT]

Okay so I was able to find a freeaware version of the eagle program and created the files but what im really wondering is each board really $20.00? I'm trying to go through seeedstudio that is. Thanks all.

Its $20 for 10 boards.

Jeff

[CrazyPuy]

Im a dunce.... =] Thanks jeff for letting me know. I went back on their website and it was right there in the title. Thanks again!!!

[Obi-dad]

Dwizum's cat4101 drivers work great. I ended up putting small heat sinks on the chips as even with the power supply voltages tuned at .6 above required voltage, they were getting warm. I used Arctic Alumina adhesive, now they only read 110 degrees at full bore.

I don't run them at full, but want to be able to drive them slightly harder over the years to compensate for the LEDs gradually losing brightness.

[TheFishMan65]

Obi-dad, I has similiar experience with my board. Was the .6 over at 1 amp or something less?

[Obi-dad]

Obi-dad, I has similiar experience with my board. Was the .6 over at 1 amp or something less?

About 700 - 750 ma (my cheap DMM doesn't read the PWM very well.

[TheFishMan65]

Ok, thanks. If you everwant to know the max current set the PWM to 100% or tie the PWM in to 5 volts and measure the current.

[CrazyPuy]

Hello again all,

My apologies if this is in the wrong thread but i figure since ill be using DWZM's board to drive my led's i could post here for some answers.

So the CAT4101 chip can drive 6 led's per string. Assuming i'll be using CREE XR-E's with a forward volatge of ~3.6-3.7 that means i would need a power supply of 22.2 A or whats available at 24A. Here is where im starting to get confounded. From reading on threads the Meanwell ELN 60-48 seems to be the standard and can run a string of 12. I understand that 12 led's and their forward voltage will equate to 44.4v which is in the voltage range of up to 48 volts.

Now in Taqpol's thread he is using the Meanwell SP 320-24 with DWZM's drivers but only 2 are populated which is why he can only run strings of 12. Regarding the power supply i don't understand how to calcuate the maximum number of LED's and/or strings the power supply can run. I didn't want to jump into the project without fully understanding it.

Thanks in advance!

[TheFishMan65]

THe ELN and SP are completely different kinds of poser supplies. I don't remember taqpol configuration (so please repeat your question if htis does not help). Did he only use 2 driver per board so each board is 2 strings of six? IN which case he might have six board for a total of 72 LEDs.

[Taqpol]

Hello again all,

My apologies if this is in the wrong thread but i figure since ill be using DWZM's board to drive my led's i could post here for some answers.

So the CAT4101 chip can drive 6 led's per string. Assuming i'll be using CREE XR-E's with a forward volatge of ~3.6-3.7 that means i would need a power supply of 22.2 A or whats available at 24A. Here is where im starting to get confounded. From reading on threads the Meanwell ELN 60-48 seems to be the standard and can run a string of 12. I understand that 12 led's and their forward voltage will equate to 44.4v which is in the voltage range of up to 48 volts.

Now in Taqpol's thread he is using the Meanwell SP 320-24 with DWZM's drivers but only 2 are populated which is why he can only run strings of 12. Regarding the power supply i don't understand how to calcuate the maximum number of LED's and/or strings the power supply can run. I didn't want to jump into the project without fully understanding it.

Thanks in advance!

I populated two of the three slots on DWZM's board, but that just means I can run two strings of six for every board. I have ten boards total to run my 120 LEDs, split over two power supplies (one for the whites, one for the blues). Since all of the circuits are in parallel you only need to supply the minimum voltage with your power supply, but all the amperage needs are cumulative.

Blue and White LEDs have slightly different forward voltages, but thats not too important since most power supplies you will be interested in for running this application will have a trim pot that lets you adjust the voltage down to the minimum you need to run your board. What matters to you is the amperage. My SP-320-24 is supposed to mean that it can supply 320 watts at 24 volts. Since watts = amperage x voltage, my power supply is capable of putting out roughly 13.33 amps, but you want to run your power supply under 80% of its maximum capability to be most efficient and extend its life so 0.8 x 13.33 amps = 10.66 amps.

Now you need to know what amperage you will drive your LEDs at. each string of mine is driven at 700 mA (0.7 Amps). In this setup EVERY STRING (not every board) will use 0.7A. That means on my doubly populated boards each board requires 1.4A, a triple board running at 0.7A per string would require 2.1A per board. Since I have ten boards (or 20 strings) I need a total of 14 Amps from my power supply (1.4A per board * 10). 13.33A was the max and big power supplies get exponentially more expensive so I decided to split my power needs over two power supplies. That means I technically only needed power supplies that could provide 24 volts and 7 Amps (168 Watts) but for the efficiency and life expectancy reasons stated above I decided to go with two oversized power supplies.

Remember, the power supply will only use as much amperage, and therefore wattage, as it needs to so you are never wasting power going with a bigger power supply.

[CrazyPuy]

Lightbulb!!! Thanks fishman and taqpol for clearing that up. I only got as far as one class of ece in college so im a complete beginner with all this stuff. Reading all these led threads has just made me jump into the hobby again. Starting small though: a small 17 gallon. I don't want to deal with moving a huge tank.

Sidenote: I just received the cat4101 chips today. WOW that's going to take some fine soldering skills... Which I have yet to develop. Haha I'll keep in touch and or start a new thread for my build. Thanks again for all the help!

[der_wille_zur_macht]

I haven't taken ANY EE courses, so don't shortchange yourself! :)

Moral of the story, Meanwell makes many, many different products. Unfortunately, here in the Reefkeeping world, when you say "Meanwell" people automatically assume you mean an ELN 60 48 LED driver.

Soldering the CAT4101 is not hard at all once you get the hang. Page through this thread, we've discussed typical approaches a few times. I find that once most people get the hang of SMT they like it better than through-hole (I do, at least).

[CrazyPuy]

Thanks DWZM!

Im on the sra site and im choosing supplies. I just wanted to make sure these supplies were good to use:

- Aoyue 937+ DWZM recomeneded =]
- Solder Iron Tip T-2C bevel style more for soldering the wires and stars
- Wire 63/37 Rosin Core .032 (couldnt find 60/40 kester 44 on the site so i think this is a comparible soldering wire)

Optionals:

- Third Hand with Tweezers
- Double Clamp Stand with Magnifier

Looking at the size of the CAT4101 and the other components that are even smaller i was thinking that the optional tools would be pretty helpful... or should i just pick up some of that blue poster putty? Input on all the selections?

Thanks!

[der_wille_zur_macht]

Obviously I like that iron, so it gets a thumbsup. I haven't tried that specific tip, but as long as it's squat and not super-fine it should be good. The solder you picked looks Ok.

As far as the optional tools - it'll depend a bit on your technique and your personal preference. I know some people that use a small vice to hold the PCB up off the table, and some people that like the "third hand" or other such tools. I don't use any of these. I put the PCB flat on a table and hold parts with hand tools - super fine tweezers, a dental pick, and/or blue-tack.

[CrazyPuy]

Thanks again DWZM!

The only soldering I've done is car wiring so I can't really say I even have a technique for PCB's yet. I think I'll try the blue tack method and see what technique forms from there. The boards will be here in 2-3 weeks so I can think about it then. The tank and stand come in this Friday though so the plumbing and acrylic work should keep me somewhat occupied.

Thanks again!

[der_wille_zur_macht]

Blue tack and the finest tweezers you can get your hands on, and you should be all set.

[CrazyPuy]

I just got the other compotents for the board yesterday evening... o_O

Yeah.. blue tack and tiny tweezers it is! Now im just waiting on the actual pcb's.

This should be fun =]

[CrazyPuy]

Hello again,

I found these two tutorials to be helpful on youtube:

http://www.youtube.com/watch?v=wQXhny3R7lk&playnext=1&list=PLD3936B2A343298F6

Can i expect this to happen with the cat4101's, ie. some kind of wicking?

and:

http://www.youtube.com/watch?v=EWeAOemTY_E&feature=related

Comments on technique and style?

[nreefer]

Is a 45 watt soldering iron enough? One of the popular vendors of LED's recommended a 100watt soldering gun, as that is what they use for building the systems they sell online.

[seti007]

Hi all, I am having some issues with my build. I have the tripple cat board assembled and to test it out, I have 6 of Steve's dual emitter LEDs connected to one of the CATs in series. Well, after applying a 5v signal to PWM it turns on and everthhing but within 5 minutes or so, the CATs overheat so horribly that one time they even smoked a bit. It still functions after I turned it off and let it cool. The Walwart supplying the 5v tends to overheat as well and turning the variable resistor (10K pot) at RSET has absolutely no effect on the intensity of the light ( I have it in series with a 680 Ohm resistor). The only thing that seems to cahnge the intensity is if I vary the 5v input. I wonder if there is a short on the board or what? Can each one of the CAT's drive 6 of these LEDS? Im driving the whole thing with a 24V 2.5A power supply.
TIA

EDIT: I let it run longer ~10 mins and it actually melted the solder behind the CAT4101 chip. Thats Damn hot !!! Something is obviously wrong and Im hoping that it may be something as simple as the number of leds Im driving.

[kcress]

Those are called linear controllers. Any power not sent to the LEDs has to come off the CATs... They can only take about a Watt. You need to tell us the Vf of the string you're driving and the voltage of the DC supply you're running it all with. It would be very helpful to know the current you're ending up with too.

[kcress]

Is a 45 watt soldering iron enough? One of the popular vendors of LED's recommended a 100watt soldering gun, as that is what they use for building the systems they sell online.

45 should be enough if you have a clue about soldering. The 100W would certainly be faster and better on the LEDs but is not as utilitarian. Like you wouldn't use it for soldering electronics.

[nreefer]

Thanks Kcress, I am shopping for one now for my 216 LED build. All the LED's are coming pre-tinned

[der_wille_zur_macht]

seti,

In addition to kcress's comments, I would try very hard to check for faults or shorts on the board or your soldering work. The situation you're describing is not typical operating behavior. Also, can you tell us what circuit you're using? You mention a wall wart and a pot, how exactly are those wired?

[Obi-dad]

Hi all, I am having some issues with my build. I have the tripple cat board assembled and to test it out, I have 6 of Steve's dual emitter LEDs connected to one of the CATs in series. Well, after applying a 5v signal to PWM it turns on and everthhing but within 5 minutes or so, the CATs overheat so horribly that one time they even smoked a bit. It still functions after I turned it off and let it cool. The Walwart supplying the 5v tends to overheat as well and turning the variable resistor (10K pot) at RSET has absolutely no effect on the intensity of the light ( I have it in series with a 680 Ohm resistor). The only thing that seems to cahnge the intensity is if I vary the 5v input. I wonder if there is a short on the board or what? Can each one of the CAT's drive 6 of these LEDS? Im driving the whole thing with a 24V 2.5A power supply.
TIA

EDIT: I let it run longer ~10 mins and it actually melted the solder behind the CAT4101 chip. Thats Damn hot !!! Something is obviously wrong and Im hoping that it may be something as simple as the number of leds Im driving.

If your power supply is adjustable, you need to turn down the voltage. I have a couple of the cheapo POTrans power supplies, they have an adjustment, and I turned them down to just above 20v. In general you need .5 above the Vf of the LED string, but the guys here recommend giving it a little more, like .6 or .7 above. So if you are dropping 19.2v on your LED string, you would set the power supply to around 19.9v. Before I turned down the voltage, they got hot.

I also put small heatsinks on my CAT4101s (using Arctic Alumina adhesive)

[TheFishMan65]

I just looked at one of Steve's LED the Vf is 3.8-4 so he is in the right range with 24 volts. Since you says dual emitter I wonder how you have them wired. Do you have 2 string of 6 or six strings of 2. I expect the second so you only are dropping 7.6 - 8 volts across the LEDs and the rest (about 16) on the CAT. If so I can see it getting hot very fast.

[der_wille_zur_macht]

Fishman, Steve's "dual emitter" LEDs are simply two emitters on the same die, in parallel. For all intents and purposes, it acts like a "single" LED from an implementation point. The "dual" part takes place inside the chip and isn't apparent when wiring or running the LEDs.

[TheFishMan65]

Thanks DWZM, I didn't think to look that up while I was there. But the description still sounds like he might have wired them in parallel rather than series. Just a thought to check.

[mm.reefs]

Hi!

If anyone have spare CAT4101 driver pcb's for sale, please PM me. I place an order with itead several weeks ago but apparently it got lost in the holiday rush.

Regards!

[seti007]

thanks Fishman and DWZM, the voltage drop for the LEDS is 3.2 -4v. Im driving one string of 6 LEDs in series with one CAT. The pot is connected to the RSET reisistor and ground. should I be driving more or fewer LEDS per CAT. I think I have a mismath and Im not using the full 24Volts being pushed into the circuit by the Meanwell powersupply. As Fishman said Im burning quite a bit inside the CAT rather than the LEDs.
Im almost 99.9% sure that these are the LEDs Steve sent me
http://www.maxlitech.com/cp_ck.asp?id=11

[TheFishMan65]

Can you measure the voltage drop across the LEDs and the current going through them?

[der_wille_zur_macht]

I still don't think the behavior you're seeing is typical. When you "overload" a CAT4101 by trying to get it to drop too many volts, the overload protections in the chip kick in and shut it down WAY before you get to the point where the solder melts or anything smokes. Also, regardless of it you're overdriving it or not, adjusting a pot between RSET and GND will affect the drive current in an obvious manner. I strongly suspect that either you have a fault on your PCB or the particular CAT4101 chip you're using is damaged or faulty - You may ALSO be overdriving it, but I don't think that's the only thing going on at this point.

[seti007]

Can you measure the voltage drop across the LEDs and the current going through them?

My damn multimeter only measures upto 200ma so Ill have to get a new one. As for Voltage, do i just take a readign while the LEDs are operational?

DWZM, i think you are right about about there being some kind of an issue with the board. I will assemble another one and see if i have the same issue? I have tried two different CATs on teh same board and have the exact same problem. Hopefully the PCB is not faulty. How many of these LEDs can one CAT drive?
Thanks!!! You guys are great.

[der_wille_zur_macht]

The CAT4101 is limited to 25v on the LED pin. That basically means you can use any input voltage up to 25v. You're using a 24v supply, so you're under the limit. What you are limited to with a 24v supply is essentially 23.5v of LEDs (leaving half a volt of drop for the chip itself). So, if you know the Vf of your LEDs, you can keep adding LEDs up to (but not over) 23.5v.

Of course this is all theoretical. LEDs tend to vary significantly in Vf so the best approach is to undershoot a bit then adjust the power supply to get the minimal drop.

[TheFishMan65]

Yes while they are on.

6 LEDs in series. You are sort of driving string of 6 in parallel (which is OK) from my understanding.

[seti007]

ok an update, I soldered a new circui tand everything seems to be workign as usual now. I attribute teh first board I assembled to my sub par soldering abilities. I also bought a better multi meter and did the current calculations. the voltage drop is 3.2v so I guess i could have 7 LEds in series so 7x3.2=22.4V if I have a power supply set at 23.9 v it should be able to drive these 7 leds. However with 6 LEDs I can vary the current from under 100ma to 800mA but with 7 LEDs the current never goes above ~400mA. Any Ideas? Im using the Rset resistor to vary the current. The chip still gets warm but not bad at all. I can tell you this much ... this is one tough chip. It got hot enough to melt the solder and still worked.

[TheFishMan65]

What is the voltage rating of the power supply and have you measured it (what is it)? Was it still turned down when you tested 7? What is the power output of the power supply?

FYI you only need .5 volts over the forward voltage so you should be abloe to go as low as 22.9 (or was 23.9 a typo).

Appears to work. YOu could ave stressed it heavliy and it may not actually behave properly in all conditions or may quit all of a sudden. IMHO replace it with a new one.

[seti007]

What is the voltage rating of the power supply and have you measured it (what is it)? Was it still turned down when you tested 7? What is the power output of the power supply?

FYI you only need .5 volts over the forward voltage so you should be abloe to go as low as 22.9 (or was 23.9 a typo).

Appears to work. YOu could ave stressed it heavliy and it may not actually behave properly in all conditions or may quit all of a sudden. IMHO replace it with a new one.

sorry that was a type, I meant to say 22.9v. the power supply Im using is a Meanwell Sp-320-24 and I dialed it to 22.9V to drive the 7 Leds. Asa for the stressed chip, Im not leaving that one on the board Im not using. I soldered a new board with a new chip so im taking any chances.
Thanks

[TheFishMan65]

What LEDs? And what is the voltage across the 7 LEDs? I am guessing that 22.9 is only enough voltage to drive them at 400 ma. So check the voltage across the the 7. I expect it will read 22.4. If so turn the supply up to 24 (ok the 23.9 you wanted sub consciously :)) and see what current you can get.

[seti007]

What LEDs? And what is the voltage across the 7 LEDs? I am guessing that 22.9 is only enough voltage to drive them at 400 ma. So check the voltage across the the 7. I expect it will read 22.4. If so turn the supply up to 24 (ok the 23.9 you wanted sub consciously :)) and see what current you can get.
OK Ill check and post back. Thanks for your input fishman.

[Hockeyman]

Anyone have any spare CAT4101 triple PCBs they would be willing to sell? Shoot me a pm if you have. If not I'll be placing an order in Feb. Thanks!

[ingoh]

Has anyone got Gerber files of the triple CAT4101 PCBs for iteadstudio?
Thanks!

[MaLi]

I have three boards left. Check the Buy/Sale forum.

cheers,
MaLi

[Spuzzum]

Howdy :)

Been reading through this thread.. very cool! :)

I'm planning on building some 3066 circuits, but have a few quick questions. While playing with the 3066 spreadsheet tool, it has IOUT, and labeled as "desired average led output current". Then there's also the Rsense values. I understand that changing the Rsense values, determines the current output.. but it seems to be independent from the IOUT.. whether I specify 350mA or 500mA for desired led output current, the resistor values don't change. Yet if I just put desired current as 350mA, but change the ESR value, I'm able to get outputs of 350mA, 500mA, 700mA, and 1000mA (with 0.167ohm resistor). That's with an input of 12v, and set for 36v output.

Am I configuring this right? Is the IOUT average the lowest it will do (350mA), with 1000mA being the max? I was planning on making the circuit so the current was adjustable.. maybe use an lm317 in "current" mode to regulate the output current from between 350mA and 1000mA using a pot. At the very least, I could use all 4 resistor values, and select using a 4-POS DIP switch.

Second question... a little confused still on how constant current driver actually works. I understand that the current adjusts itself according to voltage fluctuations, but I've also read that a driver can run a string of 12 led's.. or just 1 led.. from the same driver. So.. what exactly happens to all the extra voltage? A few volts (less than 5) I can see as fluctuation.. but what about a 20v surplus?

[Spuzzum]

Sorry about that.. should open my eyes. Was answered on the first page, post #22. :p

[Spuzzum]

OK.. deciding on smaller strings (8 per) and reduced the max output to 32v from a 12v input. But I need mosfet and transistor wired in.. never used them before. And although the design tool.xls shows a block schematic, I need wires and pins :p. I emailed OnSemi and they sent me a pdf of the ncp3063.. lower voltage version of the ncp3066.

http://i851.photobucket.com/albums/ab80/thereal_spuzzum/NCP3063BoostWithExternalSwitch.jpg

So, trying to modify DWZM's schematic, I'm not sure if I'm doing this right...

http://i851.photobucket.com/albums/ab80/thereal_spuzzum/ncp3066driver-withextrnalswitch.jpg


Does it look correct? I'm doing my digikey order on Monday, but need to make sure I understand the external switch part. Everything else is easy enough.. just not sure about the mosfet and transistor.

Also, not sure if anybody's tried, or even thought of.. I was planning on having an "adjustable" constant current.. like the Meanwells. I originally thought of a trimpot in place of the RSense resistor, but less than 1ohm would be difficult, and a rheostat for that low would be expensive. But.. using resistors in parallel.. 3x 2ohm equals 0.66667ohm. 0.68ohm gives 350mA. So adding 2 2ohm 1/2w resistors in parallel with a 10ohm 1/2w 25 turn trimpot, "should" allow for a base of 350mA, or even a little lower. And at 25 turns, that's roughly 400mOhm per turn.. should be enough to fine tune.. hopefully. :D

POT 10 ohm 1/2w 25 Turn 3299P-100LF-ND
The trimpot has a minimum of 2ohm.. at the most.


Any help with the external switch part would be greatly appreciated.


Cheers.............. :)

[Spuzzum]

Think I got it... looks like just a few modifications of the NCP3066 SEPIC DFN board...



Original...

http://i851.photobucket.com/albums/ab80/thereal_spuzzum/NCP3066SEPICDFN-original.jpg


Modified...

http://i851.photobucket.com/albums/ab80/thereal_spuzzum/NCP3066SEPICDFN.jpg

[CrazyPuy]

Hello all,

I wanted to check in with the resident experts here. I got my boards yesterday and finished soldering what I needed to. I hooked everything up and it seemed like I did the work correctly as I got everything to light up with the internal pot turned down.

I"m using a meanwell sp-100-24 with DWZM's driver and CREE XR-E's in a series of 6 for 4 strings. I tested a string with the multimeter in series and with the pot all the way down it reads .19 mA and turned all the way up it reasd .7 mA. I found it kind of odd that at max it was already at .7 mA.

Regarding the cat4101 boards I read that the chips should be okay to touch but not for an extended period of time. When doing so I can press my finger on the chip for 1-2 seconds before it gets too hot to touch.

Does anyone see a red flag that something is wrong with the pot turned all the way up and already reading .7mA and the temperature of the chip?

Any help would be greatly appreciated.

Thanks!

[TheFishMan65]

What is the range of the pot? What is the suppl voltage (24 volts)? What is the voltage of the string?

The loer current will be determined by the max of the pot. The low end possibly by the incoming voltage. I would add a resitor in sereis with the pot so you can not reach beow the minimum speced which is 550 IIRC.

[CrazyPuy]

I think it might be easiest if I post a pic of the spec sheet for the Meanwell SP 100-24:

http://img.photobucket.com/albums/v699/CrazyPuy/Randomness/SpecSheet.jpg

I'm not too sure what the voltage is in each of the 4 strings. How would I calculate that?

The pot is an internal one so I'm not sure how I would go about adding a resistor to that. Maybe I'm using the wrong terminology. I'm talking about the voltage adjustment screw on the power supply.

Hope that helps you help me? =]

Thanks Fishman!

[TheFishMan65]

Use a meter and read it. What is the sense resistor value? You set the maximum current of the CAT4101 with the sense resistor. It will not supply more current then the sense resistor allows. By turin the voltage of the power supply you limited the voltage that culd be supplied by the CAT and therefore the current. I am guessing your sense resistor was picked for 700 ma.

[CrazyPuy]

That makes more sense. The mouser part number for the resistor is 660-RK73H2BTTD7680F and has a resistance of 768 ohms.

If this part is limiting the to 7mA then its safe to assume that no matter how far up i adjust the internal pot it will always cap at 7mA correct?

This entire build has been a huge learning process for me.

[TheFishMan65]

I just typed a nice long replay and lost it.

768 ohms does limit the urrent to 700ma. Measure the string voltage and adjust the PS to .5 over for optimum efficency.

[CrazyPuy]

Fishman is helping me out with a current curiosity i have but i was wondering if anyone has had experience with this. Maybe DWZM can chime in.

The CAT4101 chip is rated up to a 1a current with a 549ohm resistor as stated in the CAT4101 data sheet. I'm currently running the 768ohm resistor in the original design but find that I have to turn my PS pot all the way up to reach the desired .7a current. This is resulting in the CAT4101 running fairly hot (1-2 second touch before burning my finger).

So the question is if i swap out the 768ohm resistor with the 549ohm one and adjust my PS pot to reach the desired .7a current, will that result in a cooler running CAT4101 chip? Also will that decrease the life of the chip or will it be fine?

Thanks in advance.

[jpccusa]

DWZM has been MIA... Kcress probably can answer this one to you.

[TheFishMan65]

What is the voltage drop of the string of LEDs at 700 ma?

[CrazyPuy]

Hey Fishman. I'll have time to test that tonight. I'll post the numbers up asap.

[OTCHU]

question about the driver with the CAT .... what is the frequency you guys are using ? I am at 1200Hz and the dimming is not that great ... when I am at the value 1 (max is 255) the led still pretty bright ! (little more than a bright moonlight). My concern is I can't go less than 1200Hz because the uP I do use (PIC18F4620) is running at 30Mhz (need this speed to control my TFT screen with touch screen)

[jpguppy]

Quick Question with the CAT 4101 Triple. I'm planning on building a setup which will use 12 XP-G warm whites, 12 XP-E Royals and up to 6 XP-E blues. I only need 5 CAT's to run these.

I have already redesigned the triple board to have separate PWM controls for each CAT with all currents at 700mA. I have also included 'blank' SMD tabs on the bottom layer that can be soldered together to connect two or all three back together. I've attached the PWM mod below if anyone is interested in checking it out for errors.

Would it be worth it to modify the board so that each individual CAT can have a separate PWM AND the resistors needed to modify the voltage supplied to each group? For example, the XP-G's running at 1A and XP-E's at 700mA? I realize this might take more than a voltage drop to accurately supply each group of LEDs. Just looking into methods to reduce purchasing costs by combining boards and components as needed.

Thanks!

[nirgos]

I have been following this thread for some time now and want to thank you all for your efforts. I ordered some CAT4101s but am yet to order LEDs. I had decided to order cree XP-Gs but now the cree XM-Ls seem tempting... There is a mention in the CAT4101 datasheet that they can be run in parallel to run a LED string with more than 1 Amp. Would it mean just connecting the led pin of 2 CAT4101s together. What happens to the PWM? should the same signal be applied to both CAT4101s? I have some 1W /350 ma leds to experiment on. Was thinking of supplying 150 ma each through 2 CATs to see if a total of 300 ma is output. Please let me know your thoughts.

[TheFishMan65]

I had not thought of PWM, but I think they could be different. However, you are probably better keeping them the same so heat issues are similiar in both chips.

[nirgos]

Thanks Fishman. I'll give it a try as you agree with the basic principle. Afraid to blow up the chip as they are not available in India and takes a while to ship here. I'll put pwm to 5v ref for a start.

[shikhyung]

Simon I think you and I are thinking a like. Is this the design you have in mind?
http://www.reefcentral.com/forums/picture.php?albumid=1411&pictureid=10223
Then replicate the everything but the 7805 and C1. How many times are people interested in? I figure and even number and have two PWM (white and royal blue). Seems like a waste to have to add the 5V circuit every time, so I lean torward a larger number, but most people are getting the 24V at 6.5 amps supply from mjpa. Which might support six if not at a true 1 amp (upto about 866 ma). Any other good power supplies out there?

From this diagram, pin 1 is left open, but it is use for dimable, correct?
Thanks.

[ghellin]

ok my driver PCBs are in and I have a few questions.

1. the power supply listed in this thread over and over says no longer available so what is the cheapest alternative?
2. I will be running 48 LEDs off of 4 different PCB's for dimming with an arduino uno. so how many power supplies would I need?
3. I will be running XP-Es and XP-Gs what resistors should I use to run at 1000 mA? (a mouser part# would be best here if possible)
4. And finally is this the cat 4101 I want from Future http://www.futureelectronics.com/en/technologies/semiconductors/analog/drivers/led-drivers-linear-mode/Pages/4593497-CAT4101TV-T75.aspx

Thanks in advance!

And I do need one more driver PCB if anyone has any.

[bradstokes]

ok my driver PCBs are in and I have a few questions.

1. the power supply listed in this thread over and over says no longer available so what is the cheapest alternative?
2. I will be running 48 LEDs off of 4 different PCB's for dimming with an arduino uno. so how many power supplies would I need?
3. I will be running XP-Es and XP-Gs what resistors should I use to run at 1000 mA? (a mouser part# would be best here if possible)
4. And finally is this the cat 4101 I want from Future http://www.futureelectronics.com/en/technologies/semiconductors/analog/drivers/led-drivers-linear-mode/Pages/4593497-CAT4101TV-T75.aspx

Thanks in advance!

And I do need one more driver PCB if anyone has any.

I ran into the same problem as I am starting my build as well.

1. After some serious looking, found this http://www.circuitspecialists.com/prod.itml/icOid/9590

2. 48 / 6 = 8 channels of leds * 1A = 8 amps, so at least 2 of those 6.5 amp power supplies

3. Someone else might want to help out here, but according to the datasheet for the cat4101 you need a 549ohm resistor, I think this would be acceptable, from mouser, 660-RK73H2BLTD5490F

4. That is the exact cat4101 I just bought.

@shikhyung : Yes pin 1 is for pwm dimming, however, if you don't want to dim just tie it to 5v.

Hope this helps.

Brad

[shikhyung]

edit. found the answer.

[shikhyung]

I have other questions.
Is there a method how to calculate LEDs needed per sq foot, w/wo optics?
How high from the water level? Guard or no guard? Thanks.

[jpccusa]

I have other questions.
Is there a method how to calculate LEDs needed per sq foot, w/wo optics?
How high from the water level? Guard or no guard? Thanks.

I know it can be daunting but try searching and reading DIY LED threads... specially the humongous Write-Up.

This thread is about the DIY driver. :beer:

[ghellin]

I ran into the same problem as I am starting my build as well.

1. After some serious looking, found this http://www.circuitspecialists.com/prod.itml/icOid/9590

2. 48 / 6 = 8 channels of leds * 1A = 8 amps, so at least 2 of those 6.5 amp power supplies

3. Someone else might want to help out here, but according to the datasheet for the cat4101 you need a 549ohm resistor, I think this would be acceptable, from mouser, 660-RK73H2BLTD5490F

4. That is the exact cat4101 I just bought.

@shikhyung : Yes pin 1 is for pwm dimming, however, if you don't want to dim just tie it to 5v.


Hope this helps.

Brad


Thanks! Still could use a little more advice on #3

[bradstokes]

Just got in my order from Mouser, http://i1238.photobucket.com/albums/ff485/judas420/smallcap.jpg

I ordered it yesterday about 2:00pm CST. Pretty fast even for being in the same state. Man these components are tiny! :fun2:

Brad

[Kevin012]

From this diagram, pin 1 is left open, but it is use for dimable, correct?
Thanks.

pleas do accept my apologise, as I’m not a 100% elec. tech, but don't have 2 left hand and not shy to learn as I do lots of DIY projects, and build already one DIY LED unit.

when building the first LED unit it came with a driver (se picture), but now want to build the driver to save some $

as it is almost the same as the one mentioned above, I’m locking for some info, so it makes more sense for me, as I’m more like, part A needs to go in spot 1 and part B in spot 2

so could need some help on revers engineering this thing, so I understand it better (as schematics is a bit hard for me)

http://i1122.photobucket.com/albums/l533/kevink012/driver/IMG_9604-Copy-Copy.jpg

I have 100 CREE led’s that I want to start putting together, I previously both this driver for $ 65, however in components it is only about $ 15 I think

so here we go:

A= negative from power supply (24V)
B= positive from power supply (24V) the bridge in between is in case I want to put a electronic dimming function on)
C= connections for a regular pot dimmer (that's on it now)
D= negative to LED
E= positive to LED

1= what the hack is this, and what douse it do
2= what is this ? is this the resistor (I found a online resistor calculator to find out what one I need) but is this the resistor yes / no) if no what is it and what douse it do !!
this one sits between the pin 2 from the driver chip and the negative

3= what is this one ? when locking with a magnifying glass it is printed don it T680 – what douse it do? ---- this one goes in the middle from pin 4 on the driver chip to the positive from the LED’s

*= 5 V DC voltage regulating chip 7805 CG
+= CAT 4101 led driver from onsemi

plan is to build one of these units to drive my XP-G’s and one for my XP-E’s (6 led’s for each LED driver chip cat 4101)


reason why I want to stay whit this driver is because I’m not a electro tech, and when I can re build this driver I have something I can copy right on the table, as schematics dot tell me anything, for me it is more like: I need 1 of part A and put it there, I need 1 of part B and put it there

[TheFishMan65]

I don't understand a bridge at B. You would use the PWM for dimming.

I htnk a lot of theunknonw parts ar capacitor for stabilizing the voltage. Sorry not real familiar with the 3 board version.

1) llok like a cap on the 5 volts.
3) I am guessing this is a 24 volt cap.
2) thius is the sense resirotr should go to ground.

ghellin - thre resitor depends on the board it has to match the board layout. There is ahcart in the datahseet that tells ohm for a varietyof currents.

[Kevin012]

I don't understand a bridge at B. You would use the PWM for dimming.

I htnk a lot of theunknonw parts ar capacitor for stabilizing the voltage. Sorry not real familiar with the 3 board version.

1) llok like a cap on the 5 volts.
3) I am guessing this is a 24 volt cap.
2) thius is the sense resirotr should go to ground.

ghellin - thre resitor depends on the board it has to match the board layout. There is ahcart in the datahseet that tells ohm for a varietyof currents.

B is there in case you have a PWM control (than the conection is going in B, as I dont have the PWM yet it is bridged)

I now have a regular pot to dim (never dimed the ligets, ony the first 3 weeks, I went from 50% to 100% light output

[ghellin]

Sorry I am not that great with this. I am using the 3 cat4101 boards I plan on using all XP-Gs and XP-Es. I will use a micro controler the arduino uno to create sunrise sunset. I want the driver boards able to push the LEDs up to 1000mA. But plan on keeping them at 700mA. I can't find the data sheet to which you are referring. If anyone has already built a 3 cat 4101 driver with a 1000ma drive capacity you parts list would greatly help thanks.

[S&KGray]

Sorry I am not that great with this. I am using the 3 cat4101 boards I plan on using all XP-Gs and XP-Es. I will use a micro controler the arduino uno to create sunrise sunset. I want the driver boards able to push the LEDs up to 1000mA. But plan on keeping them at 700mA. I can't find the data sheet to which you are referring. If anyone has already built a 3 cat 4101 driver with a 1000ma drive capacity you parts list would greatly help thanks.

The only parts you have to change to run the 3 CAT4101 driver at 1000mA are the resistors (R1, R2, R3). As bradstokes already stated, you will need 549 ohm resistors instead of 768 ohm resistors (768 ohm resistors would allow a max current of 700mA).

[ghellin]

I found the chart in the data sheet 549 ohm it is thanks!

[GeorgeDeg]

If anyone has an extra 3 CAT4101 driver board, please pm me.

[shikhyung]

What is the voltage drop of the string of LEDs at 700 ma?
Have you found the answer to this question?

[imagex]

I don't understand a bridge at B. You would use the PWM for dimming.

I htnk a lot of theunknonw parts ar capacitor for stabilizing the voltage. Sorry not real familiar with the 3 board version.

1) llok like a cap on the 5 volts.
3) I am guessing this is a 24 volt cap.
2) thius is the sense resirotr should go to ground.

ghellin - thre resitor depends on the board it has to match the board layout. There is ahcart in the datahseet that tells ohm for a varietyof currents.

hey this is the stevesled driver to the tee.. thats what i was asking a while back about how he's using all the cat4101's on one dimming source... i asked if it was possible before and everyone decided against it.. i think including you.. If i'm not mistaken that design is the exact steve's led driver i had here..

[TheFishMan65]

Boy I had a bad typing day. The CATs don't draw much current for the PWM. They have a 200k ohm resistor. So 5 volts / 200k = .025 milliamps. IIRC the arduino supply 40-50 milliamps. So an Arduino pin could drive 1600 of these.

I don't ever recall saying you can't hook up multiple dimming signals to one source. IMHO most dimming source will be capable of driving multiple driver, but check the current to be sure.