Introduction: Modular Bench Power Supply Using Old Computer Parts (Variable Outputs)

By Visit our blog!

Hello guys.

Abhay and Akshay here!

Today we are going to show you how to make this Bench Power Supply using an old Computer Power Supply. The idea behind this project was that we needed to charge our phones, battery banks as well as other portable light sources as fast as we can for shooting so we needed many chargers for that. So we decided to make this with 4- 5V 2A USB Outputs, 4 12V outputs, several crude outputs, and two adjustable voltage outputs. The adjustable output goes from 4.8V to 54V.

You can scroll down to watch all the steps or watch this video and relax back.

So now let's make this build.

Step 1: Understanding How the PSU Works

*DANGER*

In any case do not open your PSU and make sure that it is unplugged whenever working on it as it is quite dangerous and might cause you harm.

You can find these power supplies at cheap in an electronics store which sells second hand products. We got ourselves from a wholesale dealer of PC parts so it costed $2. This power supply is rated at 450W but you can use lesser rated ones too as even 200W is a lot for our use.
Every PSU has some color coded wires. Each color has a specific meaning and generally Orange means +3.3V, Red means +5V, Yellow means +12V, Blue means -12V, White means -5V, Purple means +5V Standby, Black means ground and so on which you can see in this link. It also shows you the difference between PSU’s with 20 pin or 24 pin connectors. But if your PSU has different wire colors then you can check the side of your PSU for the rating as well as which wire is what. Usually a motherboard takes about 5W power even when nothing is connected so we used a 10W Resistor to trick the PSU that motherboard is connected. And to switch it on basically for checking purposes that whether the PSU is working or not you have to basically connect a Green Power_ON wire to Black ground. We will be connecting a switch between these to on and off our Bench Power Supply.

Step 2: Supplies

The list of the components needed -

Step 3: Cut Off the Connectors From the PSU Wires

You basically need to first cut off the wire connectors off and then group them on the basis of their color. Then select what wires you need and whatnot and then cut off the excess ones.

Step 4: Design a Case Extension for the PSU Using MDF Board

Then you need some MDF board to make a basically extension for the metal case of the PSU so that we can house the extra components in it. Then you basically need to design the front of the case extension. We designed holes for the USB ports, DC ports, some space for Male headers, a switch, a potentiometer, a voltmeter, some LEDs, and the adjustable outputs.

Step 5: Hot Glue All the Components in Their Place

Then basically glue everything to its place first. We glued the boost converter and the 10W resistor to the base of the case. Make sure to keep the resistor near the Fan vents as it will get hot over time when in use. But it never gets too hot to handle so there will be fire problems. We also stuck some White LED strip inside the case so that it will illuminate the USB ports whenever the Bench Power supply will be on.

Step 6: Soldering and Making the Circuit

Now after everything has been glued to its place firmly, you can begin the process of soldering and making the circuit. The circuit is very simple, just first connect the +5V red wire to USB ports then +12V yellow wire to DC ports then red wire to the boost converter as well as the dummy load. Now connect the +3.3V Orange wire to the LEDs with some resistance like 220 ohms. As you will see in the video, the LEDs were glowing too brightly so use some higher value resistance like 1K ohm or more. Now connect the wires to the male header pins which output you want like blue, red, orange, yellow, white, etc. Now connect the potentiometer in place of the one in the boost converter. Our was a 100K ohm but you may want to check if yours different.

Now connect its output to the output ports. Then connect the switch to the green wire and at last connect everything wherever needed with black ground wire.

Step 7: After Soldering, Turning on the PSU to Check If Everything Is Working or Not

Before turning it on for a check, make sure that no two wires are touching and every connection is properly done. Then you can turn it on for a check and at this time I realized that I connected the LEDs to 5V so most of them fused instantly and I thought it to be a huge pain so I only changed one Power on off LED and left the others as it is but removed their connections. Now if everything is working it’s good but if it doesn’t then check the dummy load that if it gets warm or not. If it does not then you might need to check the manual of your power supply to know the load it needs to turn on and then change the resistor with it. If it does get warm then you just need to check your wiring and everything is connected or not.

Step 8: Hot Glue the Case to the PSU

If everything is working then proceed to close the case with the help of hot glue. Don’t shy away from using a lot of it to properly seal the case.

Step 9: Here You Go

And there you have it, a working bench power supply with lots and lots of differently curated outputs which you can customize to your needs. It also outputs high current as well as high voltage whenever you need it. If you have any problems, then shoot us with them in the comments section below.