Convert ATX PSU to Bench Supply

The standard computer power supply unit (PSU) turns the incoming 110V or 220VAC (alternating current) into various DC (direct current) output voltages suitable for powering the computer’s internal components and with a little bit of imagination it is possible to convert ATX PSU to a bench mixed Signal connector .

atx psu
Most computer PSU’s range from about 150W up to 500W so there is plenty of power. The original ATX standard connector used for powering the motherboard was a single 20-pin Molex that has all the required +12VDC and +5VDC voltages with huge output currents and short circuit protection as well as a Power-ON wire that allows the PC’s software to turn “OFF” the PSU on shut down.

Firstly and more importantly before you start to convert ATX PSU, make sure that the PSU is unplugged from the mains supply and discharged by letting it sit unconnected for several minutes before you start. This is important! as it could result in a potentially dangerous or even lethal situation due to the high voltages inside the PSU if you decide to dismantle it. Also make sure that the metal box of the PSU is correctly earthed or grounded. You are responsible for your own safety!.
We can not just simply plug the PSU into the mains supply and expect to get the required 5 or 12 volts output. The standard PC power supply unit has two safety mechanisms that prevent it from being switched “ON” without the motherboard attached.

There are several different coloured wires attached to the 20-pin ATX connector providing several different voltage outputs such as +3.3V, +5V, +12V, -12V, -5V as well as a number of black ground wires and a couple signal wires as shown in the following image along with their colour-code and description.