This can be made to power about anything! I made mine to power my 8x8x8 LED Cube (instructable to come soon) and anything else I make in the future! It is now the most useful thing in my workshop!
Computer power supply's are great as they supply a tremendous amount of power in 12v, 5v, and 3.3v. Some also have -12v and things like that, however mine did not. There are many instructables on how to make one of these, so I will not go into the details, so for the electronics part search atx desktop power supply.
However, here are the basics:
-When Building a power supply like this you have two choices; you can directly open the power supply and put the binding post directly on the atx, (like this)or you can make a box to put it all in and use the wires that just come right out the side already.
-I chose to build a box around it (the legos) because i didn't want to hurt anything inside it or hurt myself.
-Basically you have a working power supply the minute you take it out of an old computer. all you have to know is which wires to use.
Which wires do what?:
-Note that this is not the same for everyone, it depends on your model and manufacture, so just Google the pin out of yours. Mine is below.
-Yellow wires- 12 volt
-Red wires- 5 Volt
-Blue wires- 3.3 Volt
-Black wires- Ground
-Purple wire -Standby, This wire provides a 5v signal when the power supply is plugged in. Hooked to standby LED.
-Gray wire- Power switch- simply connect this to a ground to turn on the power supply. Hooked to switch.
-Orange wire- power good- the power supply runs through a cycle when you turn it on to make sure its still ok, when done this wire is turned on (originally there to tell the motherboard of a computer to continue with boot up process). This is Hooked to the Power On LED.
Here is what i did:
-The base is a big green Lego base plate screwed to a piece of wood.
-The atx is simply mounted to the top with a piece of wire.
-A 10ohm 10watt resistor to have load on the atx at all times
-I put a main power switch a standby led and a power on led.
-I originally had fuses in here as I did not want 30amps running through my projects. But they kept blowing and I ran out.... So i temporally "Fixed it".