Introduction: Cheap and Easy Bench Power Supply

There are many instructable’s about using computer power supply as a bench power supply, but most of them required to modify the power supply, like cutting the existing wires and drilling the case. If the power supply fails all the modifications has to be done again for the new supply. So I thought of making an adapter for pc power supply which has standard molex and 24 pin connectors and can give +12v, -12v, +5v, -5v, +3.3v outputs for general purpose usage.

I started this project when I bought 5 meter RGB led strip and didn't get power supply for it, and I am planning to make an arduino based led color organ so I need 12v and 5v supplies. So buying and using single pc power supply is better and cheaper than using two separate supplies.

So I decided to desolder 24pin motherboard connector from broken motherboard and make a case for it.

Step 1: Parts Needed

later that day I came across this power supply tester in amazon and someone complaining that it dose not do anything but indicating LED's and it just costs around 2.5$ and thats exactly what I need.

I decided to use this as it has all thee connectors needed and a nice case and just need a little modification to use it as a supply.

Parts needed to modify

  • Power Supply Tester
  • PC Power Supply
  • Toggle switch
  • Soldering iron
  • Wire
  • Wire cutters and strippers
  • Hand drill

Step 2: Modifying the Tester

First it is made to run as soon as it was plugged in to ATX power supply, we have to add a switch to make is switch on. Generally pin 16 or green wired pin in 24pin connector has to be grounded or connected to black wire to switch on the power supply

The trace going to ground has to be scraped off.

Their is a hole at the bottom right corner of the board, that has to be made larger to add a toggle switch.

A wire has to be added to pin16 to switch and ground to switch as shown in image

Now we have a switch to power on the supply manually now we need outputs as both the sides of board are isolated as they are designed to test the supply.

They have to be connected by soldering 5v line from one side to 5v on the other side and 12v and ground following and secured everything using hot glue

Now we can use 24 pin connector as input and molex connectors on the other side as outputs.

I soldered binding posts to the end of a molex cable to use as a standard banana plugged cables

Step 3: Using the Modified Tester

I have made a USB charger by soldering USB female jacks to a pref board and made a cardboard box and made some holes to access USB ports and connected to 5v line coming from ps-tester and two of the USB ports are also connected to standby 5v line of power supply so no need to swtch on the power supply for charging 2 devices.

As my power supply can provide only 1.5amps from 5v standby line I have made one USB port as 0.5amp and one as 1amp by connecting D+ and D- pins of usb jacks.

I have also made led color organ using arduino using this as a power supply.


pantalone made it!(author)2015-12-18

I've converted several old PC power supply units to benchtop service, and making the mods is a pain. This is a great idea to move the mods to a separate box that can be used again and again.

vamsikurre made it!(author)2015-12-18

thanks,especially when those cheap power supplies goes through abuse as bench top units