Computer power supplies cost around US$15,but lab power supplies can run you $100 or more! By converting the cheap (free) ATX power supplies that can be found in any discarded computer, you can get a phenomenal lab power supply with huge current outputs, short circuit protection, and very tight voltage regulation.
In this instructable I will show you how to quickly convert one of those many computer power supplies into something that you can use to power your electronics projects, for electroplating, for electroetching, for heating wires for foam cutting, etc.
The voltages that can be output by this unit are 24v (+12, -12), 17v (+5, -12), 12v (+12, 0), 10v (+5, -5), 7v (+12, +5), 5v (+5, 0) which should be sufficient for most electrical testing. Many ATX power supplies with a 24-pin connector for motherboards will not supply the -5V lead. Look for ATX power supplies with a 20-pin connector, a 20+4-pin connector, or an AT power supply if you need -5V.
PLEASE, YOU ARE WORKING WITH AC VOLTAGE!!! IF YOU ARE NOT SURE OF WHAT YOU ARE DOING - DO NOT ATTEMPT THIS.
These instructions were originally posted by me on http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
I finally had to package the PSU in a nicer box. The wooden book was from a local craft chain called Michaels which I lined with foil and then packaged the electronics in. I also added back the 3.3V terminal as this was useful and I missed not having that in my previous version.