Working on electronics projects can get frustrating when you realize every module need a different voltage. Some run on 3.3V, others on 5V, and more power-hungry parts might need 12V or even 24V. That means you either end up with a mess of adapters or keep swapping power supplies which is not a great solution.
I wanted something simpler for my basement workshop, where I don’t have my main bench setup. Instead of buying multiple power supplies or a commercial bench power supply, I decided to repurpose an old PC power supply. These things are cheap, reliable, and can deliver a ton of power at all the standard voltages we need. The only problem? They’re not exactly user-friendly straight out of a computer.
So in this guide, I’ll show you how to turn one into a clean, easy-to-use multi-voltage power supply that is perfect for any electronics workbench. By the end, you’ll have a single unit that gives you 3.3V, 5V, 12V and -12V, plus an adjustable output for anything up to 30V.
Tools and Materials
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- XH-M229 PSU Breakout board - https://s.click.aliexpress.com/e/_ooSKHXl
- Computer Power Supply - https://s.click.aliexpress.com/e/_ooXScYb
- SK35 Mini DC Buck-Boost Module - https://s.click.aliexpress.com/e/_oDPEAqJ
- 3D Printer - https://s.click.aliexpress.com/e/_o2CRLHt
- PETG Filament - https://s.click.aliexpress.com/e/_on9V4ld
- Assorted Screws Kit - https://s.click.aliexpress.com/e/_olBMrE7
- Soldering Station - https://s.click.aliexpress.com/e/_onuYyWn
- Multimeter - https://s.click.aliexpress.com/e/_oEOKuGF
- Electrician Screwdriver Set - https://s.click.aliexpress.com/e/_oDmBrYf
- 8 in 1 Mini Screwdriver - https://s.click.aliexpress.com/e/_oDrDD6x
- Wire Snips - https://s.click.aliexpress.com/e/_o2eJ3IF
Gathering the Components
The nice thing about this project is that you probably already have some of the parts lying around. The main piece is an ATX power supply from an old computer. Mine is rated at 750W, but anything you might have will work fine, even one that is 10 years old. These supplies give us all the standard voltages we need: 3.3V, 5V, and ±12V, with plenty of current for most projects.
The other key part is a breakout board that converts the power supply's messy bundle of wires into something usable. I'm using the XH-M229 board, which has screw terminals for each voltage rail, plus an on/off switch. It's not perfect, but it gets the job done. For voltages outside the standard range, I added a small adjustable DC-DC converter module that lets me dial in any voltage I need between about 0.5V and 30V.
You'll also need some basic tools: wire cutters, a screwdriver, and a soldering iron. If you want a cleaner setup, a 3D-printed enclosure helps keep everything organized, but a plastic project box would work too. The goal is to make something sturdy and safe, since we're dealing with mains power and high currents.
Preparing the Power Supply
Before doing anything else, unplug the power supply and make sure to handle it with care as those big capacitors can hold a dangerous charge even when switched off.
A standard ATX power supply has way more cables than we need, SATA, Molex, PCIe, but we only care about the 24-pin motherboard connector and one of the 4-pin 12V cables. I clipped off all the extra wires close to the board so they don’t get in the way. Make sure to double-check which wires you’re cutting by following them back to the connector - you don’t want to accidentally cut the wrong ones.
The 24-pin connector goes to our breakout board later, and the 4-pin 12V cable will power our adjustable DC-DC module. I soldered the 12V wires together to make a thicker cable (more current capacity), then trimmed them to length.
Modifying the Breakout Board
The XH-M229 breakout board is handy, but I wasn't a fan of the tiny screw terminals as they make it hard to quickly connect test leads. I wanted to swap them for banana jacks, the same kind used on lab power supplies. Turns out, it's not quite that simple. The original terminals use M2 screws, but the banana jacks I bought need M3 holes.
For now, I left the original terminals in place since I didn't want to drill out the plated holes. Instead, I'll order the right size jacks later. In the meantime, the screw terminals work fine, just not as convenient. The board does have nice fused outputs for each voltage (3.3V, 5V, ±12V) and a clear power LED, so it's still perfectly usable.
Assembling the Enclosure
A messy power supply is annoying to use, so I wanted everything housed neatly in one unit. I found a 3D-printed enclosure design online that fits the ATX power supply, breakout board, and DC-DC module. Since my power supply model was slightly different, I had to tweak the design by shortening the mounting bars in my slicing software.
The assembly is straightforward: screw the power supply into the base first, then mount the breakout board to the front panel. I left off the optional cover for the breakout board because I like the industrial look of exposed electronics. The DC-DC module is mounted in its separate case that is first screwed together to the power supply front holder.
Everything fits snugly with just enough room for airflow.
Testing the Power Supply
To test out the power supply, I plugged it in but kept the switch at the off position at first. When I flipped the switch, the breakout board's LED lit up immediately and the display also lit up on the SK35 module.
Grabbing my multimeter, I checked each output so that I can confirm that we had all of the voltages on the right pins. Only the negative 12V output was slightly above -12V but everything else was within specs.
I also tested the SK35 module by setting it to different voltages and confirming them with my multimeter.
Flicking the switch again, turned off the power supply which concluded the test and I can now declare the project done.
Final Thoughts
This converted ATX power supply has become one of the most useful tools in my workshop. It's not fancy, but having all those voltage options in one unit saves so much time compared to juggling multiple wall adapters. However, there are things that can be better.
The biggest limitation is the lack of current limiting on the breakout board. Unlike a proper lab supply, this can deliver full power immediately. You can still use current limiting at any voltage using the SK35 module, but this is sometimes tedious to be set.
If you are just starting with electronics, this power supply will definitely take you far into your journey and it is also a fun little project for the weekend. If you liked this build, make sure to subscribe to my YouTube channel so that you can also see my future projects.
