arduino - Powering LEDs with a computer's power supply

I have 10 of these boards OctoBright CYANEA v2.0 connected in series, controlled by an Arduino.

Powering one or two off of the Arduino 5v pin has worked for testing. Now I want to scale it up to 10x boards. I been told that a computer power supply should be able to handle the load from all 10 of these boards in series.

Each board at max brightness consumes 500mA. 10 * 500mA = 5 Amps max

My questions are;

• Do I need to add any power conditioning to the output of the computers power supply?


• Can I directly connect the 5v rails from the computer's power supply to these boards?


• Anything I should know before I wire this up?


• Can I power the Arduino from the same 5v rail of the computers power supply?

Answer

The computer power supply is very likely to have a 3.3 Volt output, and you should use that for the LED power. Even the smallest ATX type power supply should have no problem delivering 5A on the 3.3 Volt rail (But check the specs).

If you have to use a 5 Volt rail, the problem won't be your power supply, it will be the LED current sinks. The forward voltage drop of the LEDs will be between about 2.1 and 3.3 Volts depending on the color. If you apply 5 Volts, the 'extra' 1.7 to 2.9 volts are going to have to be lost as heat in the controller current sinks. The controller has 24 of these sinks and it is going to become very hot very soon.

If you can't dissipate enough heat from the controllers, a simple fix could be to use one or more linear regulators to drop the voltage from 5 to 3.3 Volt or so. It might be easier to dissipate heat from the voltage regulators than from the controller chips.