Help making a high powered RGB Lighting system for my highschool

Why not.. Once you get them, send me email. sooner is better.

Cool, thanks neurostar. Trying to find some adapter boards that aren't too expensive yet at the same time not wait a month for delivery from Thailand.

neurostar:
OK. that was it. I think you see all these drivers are basically very similar. Since designing is a part of your education, I would recommend chips from national semi or linear tech, simply because you have a tool to simulate your circuit with the chip. You can learn a lot by checking and poking signal here and there. Many of those signal are hard to measure even with good oscilloscope. Once you understand one chip, you will understand rest of them easily. Designing proper value of parts need some calculations. Write down all the equations you see from datasheets. Later you will also find all those equations are same regardless of manufactures. Start from a reference design such as evaluation kit of a chip. PCB design of switching power is also very important. Careful on the SW - diode - GND (input capacitor) which need to be short length. You want to have big GND pour bottom of those switching circuit to minimize EMI. Thermal vias around the chip is also critical. If you don't pay for your PCB, 4 layer PCB is also good idea. For current sensing resistor, check Kelvin trace. That's what I can think of right now. I hope that helps little.

That's what I've been doing. Haven't been using the simulators though, just been using the reference PCB design and modifying it to my needs. I like you idea of 6 seperate PCBs, one for each PWM channel. It seems like a much nicer and neater idea.

I live in Canada but I think I will just use a PCB assembly service. While I want to keep costs down, the school recognizes that the professional equivalent of this lighting system would cost a lot of money so as long as I justify all of the costs there won't be a problem. A moderate budgetary increase to go with a PCB assembly service is easily worth saving the potential failure of the project if I have trouble with the soldering. Additionally, even if I did manage to solder the chips I am leaving to U of T Computer engineering next year and thus I won't be able to fix the board if a mistake in my soldering causes a short. Finally, if the school wants to expand the LED array it would be very easy for them to simply order another copy of my design from the supplier.

Any suggestions for a good Canadian PCB assembler?

Try posting the question as a new thread, maybe a fellow Canadian can offer a suggestion; its bound to me missed buried 3 pages down in this thread.
Also try asking the folks at dipmicro.com, or solarbotics.com, see if they can do it or offer suggestions.

Switching plans again. I found this beauty of an LED driver:

Three individual 750mA PWM outputs.

I will construct one PCB per light, and then use a terminal block to split the PWM signal from the Arduino. That way, If the lighting array needs to be expanded you can simply add another board and wire it up.

I'll also be using 30W RGB LEDs, they take 28-33V in, so I will use a +36V PSU.

Thoughts?

The LEDs use 33V max, so you plan to use 36V? Seems like planned overstress to me. Something has to dissipate that extra voltage.

Pay attention on the recommendations for the unused channels also (for your future expansion).

Watch this in your PCB layout:
"The exposed pad on
the bottom of the package must be soldered to a ground
plane. This ground should then be connected to an internal
copper ground plane with thermal vias placed directly
under the package to spread out the heat dissipated by
the LT3496."
"The exposed pad of the package is the only GND terminal of
the IC and is important for thermal management of the
IC. Therefore, it is crucial to achieve a good electrical
and thermal contact between the exposed pad and the
ground plane of the board."

charliehorse55:
Switching plans again. I found this beauty of an LED driver:

http://www.newark.com/linear-technology/lt3496ife-pbf/ic-led-drvr-tssop28/dp/07P8434

Three individual 750mA PWM outputs.

I will construct one PCB per light, and then use a terminal block to split the PWM signal from the Arduino. That way, If the lighting array needs to be expanded you can simply add another board and wire it up.

I'll also be using 30W RGB LEDs, they take 28-33V in, so I will use a +36V PSU.

Thoughts?

Obviously, you didn't read what I wrote carefully. LT3496 is the chip that I used in the high power RGB LED shield. Again, I already published the design of circuit. You can just use driver part of the shield. http://arduino.cc/forum/index.php/topic,51887.0.html. You can not hand-solder LT3496, it has to be reflow due to GND. You have to find someone can do it for you. If you make only three of the driver, total cost of whole thing (PCB, parts, and assembly) will be likely higher than cost of three shields.

I did read what you posted quite carefully, I just didn't catch the exact chip name. I will be running 6x 30W LEDs from 6 separate PCBs.

Also, I want to design my own circuit as this is a school project and I need something for the teacher to mark.

Finally, your circuit did not implement the Open LED protection feature of the chip, which I will need with my setup as it is entirely possible that someone leaves an LED string un-attached.

Your circuit will help though, I will modify it to my needs.

Thanks.

Open LED protection is not necessary for buck design unless you want to arbitrarily limit the output voltage. It is over voltage protection(OVP) for boost and buck-boost design. Run the circuit from LTspice, you will understand what it does.

Thanks again. I thought that it didn't make sense for buck but thanks for confirming. Makes the circuit a little simpler.

EDIT: And what is the maximum input voltage for driver? A 48V input would work great for my needs.

charliehorse55:
EDIT: And what is the maximum input voltage for driver? A 48V input would work great for my needs.

As in data sheet PVIN max is 45V. If you use same power for VIN, you are limited to use 30V.

Okay, I guess I'm stuck with the slightly more expensive 36V/300W PSU.

I assume the actual driver IC doesn't use much power so I can simply use two 200m ohm resistors to make a voltage divider for it to run it off the +36V?

EDIT: That won't work, but possibly with higher ohm resistors? I doubt the IC draws more than 2-3W of power anyways.

There are reasons why people don't use a simple voltage divider as a voltage regulator. It is not matter of efficiency. If you use high ohm resistors to reduce the resistor power dissipation, there are high voltage drop across the resistor depending on current draw. When LT3496 draw varying current especially during PWM, you will have huge fluctuations on VIN.

Right, so a 12V VRM is a better idea.

Why 12v? You want to use as low as possible, If you are going to use switching voltage regulator. Linear voltage regulator won't work, because of high voltage difference between In and out. I think you can use 5V from Arduino, anyway you need to power Arduino with lower than 12V.

I was going to power the arduino through the USB interface. The only thing I'm going to be doing is driving 6 PWM outputs and 6 digital outs, no LEDs or other devices. The 2.5W a USB connection can draw should be enough for that right?

Unless the driver IC uses <0.25W each, I won't be able to run them off the Arduino because I will be using 6-8 of them.

USB power may not enough. Computer USB supply normally 500mA max, and LT3496 need 80mA max based on my measurement. You can just buy 3.3 or 5V power adapter.

Okay, I have done a major re-work of my driver board.

I am going to use the same LT3496 driver, but in boost configuration so that I can use a +12V input. This will also negate the need for a separate 5V power supply as the LT3496 can be run from 12V without issue.

I have also decided to switch to an I2C interface. I'm trying to find a chip like the ATTINY85, but runs from 12V. If that's not possible I can always power the chip from the Arduino as it takes <3mA at full load, but it would be much neater and easier to use a chip that can be run from the main +12V connector (that comes from a computer powersupply).

I have now figured out that I will need a 5V source for that ATTINY85 so I have decided to use the +5V rail from the powersupply and power each board with a molex connector.

Should I power the LT3496 with +12V or +5V? I have access to both on the board.

Also, is there a way to flash the board so that when it is not plugged into a computer it executes some simple code? I am going to attach some 10k pots to the analog inputs and I would like the board to automatically read those values and run the lights accordingly if no computer is plugged into to control them.