PSU Benchtop Supply

If you haven’t built one of these yourself yet, this one here is a real forehead slapper.  Create a cheap benchtop power supply from a standard ATX computer PSU.  In my case I did it completely from stuff I just had lying around.

Difficulty : EASY - SAFETY WARNING, Shock Hazard
Time: 30-40minutes

Most of you reading this have (or know someone who does) an old PSU lying around collecting dust.  The one I used was a 200W dinosaur that I pulled out of some 266Mhz gateway machine that was made in like 1996.  I gave it some new life by pulling together just some parts I had lying around the computer salvage yard in my basement.

Materials:

1 – Old ATX PSU

1 – Automotive Toggle Switch

1 – LED

1 – 330ohm resistor

electrical tape or shrink tubing

Tools:

Soldering Iron

Cordless Drill and drill bits

Super Glue

First thing you need to do is crack open the case and remove the cover.  A quick word on safety.  Even though this is an extremely simple project, some of the components inside the PSU are EXTREMELY dangerous.  It is suggested that you properly discharge the larger capacitors before you begin working on the PSU.  A quick guide on how to do that can be found HERE.  Once you’ve discharged the caps, you need to find a suitable position to mount the Switch and LED. Drill the holes out for your switch and LED be mindful that you need plenty of clearance for the wire to be routed behind them.

Next, on the main board harness, find 2 black Ground wires, the green Power On wire, and one red +5V wire.  Cut them off the clip, and pull them out of the harness and back inside the PSU case .  Pinouts of what the rest of the wires do can be found HERE.

Solder the green power on wire and one of the black ground wires to the toggle switch, and then mount the toggle on the case cover.

Now solder the cathode of the LED to one end of the 330ohm resistor.  We need the resistor to control the current going through the LED.  Solder the other end of the resistor to the Red wire.  now solder the anode of the LED to the black wire.  Insulate with tape or shrink tubing.  Put the LED in your hole and super glue in to place.

Route the wires and replace the cover and you’re done.  Keep in mind that when you get things for cheap they’re not always perfect.  The unit I used in particular does not have exactly the +5V or +12V that the lines are supposed to give.  It is suggested that you incorporate a potentiometer across the +12V and -12V connections allowing giving your an adjustable 24V range to play with.  My suggestion is check your voltage with a DMM before hooking it up to your work.