Computer power supplies cost around US$30, 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 reasonably tight voltage regulation on the +5VÂ line.
I found an old 420 Watt Power Supply:
The maximum output(A) per voltage should be written on your Power Supply :
If you are not sure if the Power Supply is still working you can test it by shorting the green wire to any black wire, this method works for the 20-pin and 24-pin ATX Connector :
Then plug-in some PC accessory or fan to test if it turns on
If the fan spins, your Power Supply is still OK!
| Red | +5V |
| Yellow | +12V |
| Orange | +3.3V |
| Blue | -12V |
| Black | GND |
First, you want your Power Supply to be on all the time… this can be done by connecting/soldering the green wire to a black wire :
For extra protection, you could wrap it in tape or shrink wire.
First, open your Power Supply and cut all the zip-ties and connectors :
Now tie all the corresponding colors together
Lead the wires back out of the enclosure and close your Power Supply
Screw your Power Supply back together and you now have a cheap very powerful Bench / Project Power Supply
To power an Arduino, I recommend using a plug (DealExtreme)
connect a black(GND) wire to the (-) and connect a red(+5V) wire to the (+):
Connect your Arduino:
You now have a project Power Supply.
