Modified ATX PSU

Feb 1, 2009

In anticipation of my Arduino development board arriving, I decided I will definitely need a decent power supply. I have loads of old adapters laying around from phones, routers and other old devices, but these are usually quite low voltage and current. I wanted something with a bit more juice, something with some nice high voltages that could really pack a load!

Admittedly not the best thing to be mixing with microcontrollers, but I'm sure at some point I will be wanting to drive some chunky motors or solenoids for whatever reason, and will be sure to keep it isolated using relays, or even transistors or optocouplers.

Then it hit me, I have a few old PC cases and power supplies kicking around, these give out all sorts of voltages and are quite powerful. I knew someone must have done this before, so had a quick chat with my good old friend Google, who pointed me in the direction of two great resources, here and here.

Generally for anyone with a basic understanding of electronics (and you shouldn't be taking apart power supplies if you don't have) the project was relatively simple - just wire the relative wires to connectors on the side of the case! There is also a couple of wires that are ideal for standby and power on LED's. Everything is explained in the two resources shown above.

Two key points I will mention is that most power supplies will have what is called a sense wire which is connected directly to a supply wire, but when you cut all the connectors off you will be breaking this connection, so don't forget to reconnect it otherwise the power supply won't start up. Secondly the voltages will probably be a bit low, this is because most switching power supplies need a load to function properly, in this case it was achieved by putting a 10ohm 10W wire wound resistor across 5V and ground, this pulled the voltages up to what I consider a reasonable tolerance.

So here it is, 300W of multi voltage output :D