Step 12: Build a power supply
PC power supplies are nice, because they have regulated 12V and 5V rails with high Ampere ratings.
You can use either a regular AT or ATX power supply or and old external hard drive enclosure.
If you want to use an ATX power supply, you have to connect the green wire on the motherboard connector to ground (black). This will power it up.
External hard drive enclosures are especially nice to use as power supplies. They already have a convenient enclosure. The only thing you have to do is to add external power terminals.
Power supplies have a lot of wires, but the easiest place to get the power you need is through a molex connector. That is the kind of plug you find on hard drives (before the age of S-ATA).
Black is GND Yellow is +12V Red is +5V
Here is an image of our lab PSU. We have 12V output, 5V output with an ampere meter and 5V output without an ampere meter. We use the second 5V output to power an 80mm PC fan to suck or blow fumes away when we solder.
We won't get into any more details of how to make a power supply here. I'm sure you can find another instructable on how to do that.