DIY LED lighting for a 55gal long planted Tang tank

[RelatedToTheFish]

Hi. I'm new to the hobby and I have decided to try my hand at LED lighting. I have a standard 55gal long Tanganyika Cichlid community tank. It's planted with Val and Lotus at the moment, I was considering adding some Java fern as well to some of the holey rock in the tank. It's currently lit by two 8 watt 12" fluorescent bulbs. It's nice, but I'm a nerd. I want full control over the lighting, color and brightness.

There is so much wonderful information here on LED builds. I'm currently reading through, but as I get closer to deciding on supplies I thought I'd ask for opinions.

Right now I'm gravitating towards cheap (component-wise) and heavily DIY.

Supplies:
LEDs: LedFedy.com Chinese "Bridgelux" 3W
Heatsink: 2"x4"x12" Rectangular 6063AL Tubing
Fans: 50mm Case fans side mounted into the Tubing
Drivers: CAT4101 - 1 A Constant-Current LED Driver with PWM Dimming
Power Supplies: LiteOn 24V 4A power brick (or other online auction similar brick)
Controller: Arduino Nano
Clock: DS1307 Real Time Clock Module for Arduino

White LED Mix: (6 and 6 per 24" side of tank)
14 - 18000K Cold White 3W
14 - 3500K Warm white 3W

Spectrum Filler: (one cluster of 3 per 24" side of tank)
2 - 660nm Deep Red LED 3W
2 - 400nm Violet LED 3W
2 - 500nm Turquoise LED 3W

Driver(s):
I had an electrical engineering course back in college, but the only two things I remember from that class were "blue smoke is bad" and the lab where I wired a set of T-Bird tail lights. This project is my way back in and I'm not afraid to spend some quality time at a soldering station to do it.

That said, I'm having trouble figuring out the best way to power my LEDs. I have mismatched counts and voltages (for red) and most of the DIY help is aimed at matched sets of LEDs. Add to that I want each color to be addressable individually. That is five channels with three different sets of parameters. Also I want to make sure they are powered at about 70% for longevity, which means a current of around 500mA. It look like that is not common for any commercial LED drivers or power sources. So where should I start?

---

This may be a case of "you get what you pay for" but usually I find starting cheap a good learning experience. Still, if anything I picked is going to just make this a nightmare, I'd rather learn than crash and burn.

I'm open to component changes, recommended reading, constructive criticism, or any other ideas you may have. Thank you for your help.

[iano7000]

Well the arduino nano is a good starting point. It has 6 PWM outputs, so with a mosfet switch you could dim and individually control each set of LEDs.

As for power supply, you would need two separate voltage levels. Then you could run three chains of spectrum filler LEDs off one voltage in parallel, and the other two chains of white LED mix off the other voltage in parallel.

After you find out what voltage you need for the two chains, you can source a power supply of digikey or mouser. I think you have a good start. I completed my own DIY setup using an arduino Mega 2560.

[magnum]

As for building your own driver, check out this link.
http://www.reefcentral.com/forums/sh....php?t=1759758

[RelatedToTheFish]

Originally Posted by iano7000

Well the arduino nano is a good starting point. It has 6 PWM outputs, so with a mosfet switch you could dim and individually control each set of LEDs.

As for power supply, you would need two separate voltage levels. Then you could run three chains of spectrum filler LEDs off one voltage in parallel, and the other two chains of white LED mix off the other voltage in parallel.

After you find out what voltage you need for the two chains, you can source a power supply of digikey or mouser. I think you have a good start. I completed my own DIY setup using an arduino Mega 2560.

Thank you. I'm going to try and work this out below. If I'm off base, let me know.

Originally Posted by magnum

As for building your own driver, check out this link.
http://www.reefcentral.com/forums/sh....php?t=1759758

Thank you, too. I've looked at that thread briefly before and got confused by the sheer amount of methods. CAT1401 seems to be the gold standard, but the STCS1 looks enticing given the example circuit is 500mA. Any circuit junkies out there have advice for me on what might work best?

---

Alright. It's been a while so let's see if I can get this right. Additive for the forward voltages and dividing current for each parallel string?

Both the whites have a 3.2V to 3.6V forward voltage. That means if I use the STCS1 I have a range from 4.5 to 40V available. Let's say I go for a 24V at 1A power supply (or will the loss from the circuit take my parallel current below 500mA?)

24Vcc / 3.4Vf ~ 7 LEDs per string
1A / 2string = 500mA per string

So one power supply and 2 strings could get me one half my tank in whites? What happens with excess voltage would the 2 STCS1s need to be sunk somehow to dissipate that? Also I hear a lot of advice warning against parallel strings. That loss of one string or even one LED can blow the whole thing. Would that mean I would need some current-limiting fuses or could that be worked into resistors in the final circuit?

Now we move on to where things get odd for me. If we're working on one half at a time, I have one each of the the spectrum fillers.

Cyan 3.2 to 3.6 Vf
Violet 3.2 to 3.6 Vf
Red 1.9 to 2.3 Vf

All of those sit below 4V and can't be driven by an STCS1. So what do I do here? I've looked at using MOSFETs as a possibility and a really low voltage source. Is that the way to go? Or maybe a higher amperage power source, say 2.0A and a couple DC-DC converters to get 3.3 volts for the Cyan and Violet?

[O2surplus]

You could use a CAT4101 based driver and simply add a few more red leds to make up for the difference in forward voltages. The Cat4101 is rated to drive strings of leds up to 25 volts. With that knowledge, you could drive 6-7 "white", "cyan" or "violet leds per string. The "red" would require at least 8 per string to keep all the Cat4101's happy with a low voltage drop.
You could power your lighting system with a Meanwell 24 volt 6.5 amp supply. They're available for cheap on FleaBay.

[RelatedToTheFish]

Originally Posted by O2surplus

You could use a CAT4101 based driver and simply add a few more red leds to make up for the difference in forward voltages. The Cat4101 is rated to drive strings of leds up to 25 volts. With that knowledge, you could drive 6-7 "white", "cyan" or "violet leds per string. The "red" would require at least 8 per string to keep all the Cat4101's happy with a low voltage drop.
You could power your lighting system with a Meanwell 24 volt 6.5 amp supply. They're available for cheap on FleaBay.

That's true and that circuit would be a heck of a lot simpler. I have seen your work with the Cat4101, and it seems easy enough to follow. Especially with all the circuit diagrams and parts lists you have been nice enough to share, O2surplus. Thank you for that.

The only problem I have is the filler colors can really crowd out the white if they're not used very sparingly. I could maybe go as high as two of each filler per side, but any more would be pushing it. Could you substitute a high wattage resistor for the additional LEDs to even out the voltage?

        --O--O--O--O--O--O--<R1>--
        |                        |
+24V----|-O--O--O--O--O--O--<R2>-|
  |     |                        |
  |     |-O-----------------<R3>-|
  |     |                        |
  |     |-O-----------------<R4>-|
  |     |                        |
  |     --O-----------------<R5>-|
  |                              |
  -------------------------------|

R1 = R2 = 7.32 ohms [Whites (3.4V)]
R3 = R4 = 45 ohms [Violet & Turquoise (3.4V)]
R5 = 45 ohms (?) [Deep Red (2.3V)]

[O2surplus]

Originally Posted by RelatedToTheFish

The only problem I have is the filler colors can really crowd out the white if they're not used very sparingly. I could maybe go as high as two of each filler per side, but any more would be pushing it. Could you substitute a high wattage resistor for the additional LEDs to even out the voltage?

It's not really a problem at all. There's no need for any power wasting resistors either. All you need is the ability to adjust the current to the "red" leds to compensate for there being more of them. You can set up the Cat4101 based driver with a potentiometer for infinite current adjustment. That way you can adjust the overall "color temp" of your lighting and still use PWM dimming for Sunrise/Sunset dimming.

[RelatedToTheFish]

Alright. I'm getting closer to what I want. Thank you iano7000 and O2Surplus!

So I'm taking down to half of the tank at a time to that I can play with it with less components at a time. In the long run it will cost more having to double up on power supplies, controllers, ect. But I want to take this one small step at a time.



'Transformers': LM2596 step down transformer.
Power source: Fleabay 24V 3A brick supply

I'm leaving the CAT4101 as black box for now until I can figure out the rest of the components.

I think I'd be shorting myself current if I run the Ardiuno in parallel... But I like the idea of using a inexpensive standard power brick if possible. And do the fans need anything to protect them from too much current?

[iano7000]

I think O2surplus is right on the money. CAT4101 use less support circuitry, and seems very easy to use. Less wiring too.

If I were to build my own controller to the specs you have given, I would do something like this.

[O2surplus]

Ditch the transformers, all you need are a couple of *7805 voltage regulators (5V) for powering the single colored leds, and a *7812 voltage reg (12V) for powering the arduino and a cooling fan. Here's a link to the ones I use all the time- they're rated for 1.5 amps ( more power than you'd ever need)

12Volt- http://search.digikey.com/us/en/prod...8-1-ND/1204662

5 Volt - http://search.digikey.com/us/en/prod...6-1-ND/1204660

[iano7000]

You won't need any current limiting for the fan. Its a motor and builds up something called back EMF to limit the current from shorting out. That's a wiki page you can look up, and a very broad topic. With your fan's configured in series like that, they will operate at 6 volts, or approximately half speed.

I also think your 3 amp power supply won't be enough.

Doing a little math I get:
LED strands x5 @ 700mA each = 3.5 Amps
Fan x2 6V @ 150mA (a guess as it is configured in series) = 150mA

Mind you, every LED posting I have seen, the user ends up lowering their power output to 20-30% of maximum so they don't create an algae farm. But in order to operate at full power, you would need 3.65 amps. I would settle on a 4 amp power supply, or a 7.5 amp with the intention of adding more LED strings in the future. I don't think the cost would be that different.

The pre-packaged variable power supplies are not a bad idea. If you don't have the supplies, getting the decoupling caps for 7805's can be a pain, and protoboard for soldering is expensive (at least on digikey). Another advantage is you could also dial it in for the exact voltage that you want. You are paying more, but you don't have to get into that engineering level of detail. The trade off might be worth it. This could be used to power the fans and arduino, but a LM7812 would work as well.

In this application, you don't need the isolation that the transformer provides. To save yourself a headache in troubleshooting, I would tie the ground of the individual LED strands, violet, cyan etc. to the common ground of the circuit. That is if you decide to go with the transformers.

[RelatedToTheFish]

Originally Posted by iano7000

You won't need any current limiting for the fan. Its a motor and builds up something called back EMF to limit the current from shorting out. That's a wiki page you can look up, and a very broad topic. With your fan's configured in series like that, they will operate at 6 volts, or approximately half speed.

I also think your 3 amp power supply won't be enough.

Doing a little math I get:
LED strands x5 @ 700mA each = 3.5 Amps
Fan x2 6V @ 150mA (a guess as it is configured in series) = 150mA

Mind you, every LED posting I have seen, the user ends up lowering their power output to 20-30% of maximum so they don't create an algae farm. But in order to operate at full power, you would need 3.65 amps. I would settle on a 4 amp power supply, or a 7.5 amp with the intention of adding more LED strings in the future. I don't think the cost would be that different.

The pre-packaged variable power supplies are not a bad idea. If you don't have the supplies, getting the decoupling caps for 7805's can be a pain, and protoboard for soldering is expensive (at least on digikey). Another advantage is you could also dial it in for the exact voltage that you want. You are paying more, but you don't have to get into that engineering level of detail. The trade off might be worth it. This could be used to power the fans and arduino, but a LM7812 would work as well.

In this application, you don't need the isolation that the transformer provides. To save yourself a headache in troubleshooting, I would tie the ground of the individual LED strands, violet, cyan etc. to the common ground of the circuit. That is if you decide to go with the transformers.

I'm planning to current limit using a resistor on the CAT4101's to a max of 500mA per strand. I saw that a rule of thumb for LED lift was around 70% of max for cool running and a good lifetime. But you are right, throw in the fans and the Arduino and I'm running short. I'll start sourcing at around 4A. Would I be better doing a regulator down to 12 and running the fans parallel?

I keep seeing things over linear regulators being inefficient. Does burning off all the extra voltage really matter? Also $0.20-$0.50 is definitely much cheaper than $4.00 a pop when comparing regulators to step down converters.

I've also seen some Arduino threads about making sure the Arduino has well regulated power. Is a linear regulator at 5V enough, or do I need to be looking at DC-DC converter ICs that do a strict 5V @ 500mA?

Either way I got Eagle this weekend and I'm teaching myself. I'll see what I can come up with. Thank you jcgd and O2surplus for posting schematics on ReefCentral that I can learn from.

[O2surplus]

Here's one that I drew up a few weeks ago, but I haven't got around to having it made yet. Let me know if you'd like the build files for it and I'll post them for you. I found that it was easier to learn EAGLE when I studied other's PCB designs.

[RelatedToTheFish]

Originally Posted by O2surplus

Let me know if you'd like the build files for it and I'll post them for you.

That would be fantastic! Thank you for offering.

[O2surplus]

Here ya go! Play around with them all you like. Having the schematic in hand is the best part, as you can always use it to create a PCB design that is truly yours.