Introduction: How to Build a 24V Power Supply From 2 ATX PSU

About: Working on a 40W laser, repraps, and IoT

Two ATX PSU = One juiced DIY 24 Volt DC Power Supply

Before we get going, i have to make it clear that this is by no means the safest solution, and that might even be and under estimation. I am no expert, and copying my steps is at your own cost. If you are in doubt don't try it.


This is my first instrucable since i couldn't find this project anywhere i thought i might aswell document it with pictures.
Also English is my 2nd language so bear with me.

Well, what you get when done is a 24 Direct Current (DC) Power Supply (PSU).

Parts list:

2* XXXX W ATX power supply.


A good length of mains cable.

Scrap wood or what you think is suitable.

Common tools (screw driver/hammer, saw, nails/screws and so forth)

Soldering iron with accessories or alot of male/female connectors.

Nice to have list:

A clue gun.

Multimeter. I nice to test things out before frying electronics.

Common sens.

Everything was sourced for free except for tools. This made this a perfect fit for my needs.


If i missed something please point it out, but if you have the above tools i have no doubt in my mind that you can make it.

Look all syncronyms and words up on wikipedia before asking.

Step 1: Theory / Build

Since there more and more computers laying around the junkyard theres more and more ATX PSU to get for free.

The higher the wattage  described on the PSU the more amperes it can pull when done.
Small PSU will be suitable for testbeds where bigger could be used to weld or power a CNC (as I'm doing).

Before going any further if you scavanged your PSU like I you should test them out before spending more time with them.

Short PIN 14 (on standard ATX PSU) to any ground wire. It will make the PSU turn on, test with a multimeter. For any iregular PSU search around for howto-short-a-PSU. For pictures (i forgot to document that step) just take alook around instrucables and you'll be able to see how to do that step. Theres different way of doing this, but they all do the same job.

There also alot of chatter about how you keep the woltage steady without spikes. Again see other instrucables since most PSU are different an all have different build in features.

I went with a KISS solution.

The two PSU is now called PSU A and PSU B

Since theres some capacitors, inside the cabinet, which can still have a charge in them, wait a while before working with the PSU if they have been powered recently.

Now tear apart both of them. You do this to clear any ground connection there might be, remember to remove the ground (GND) from the mains line you are powering the units with, then you are sure that part of the project don't go FUBAR on you. I would not reuse the metal cabinets, period. Theres way the much risk in them making a contact with any loose wires. Which could result in frying you/electronics.

We can then procced to connect the +12 V wire from PSU A to PSU B GND wire, that will give PSU B GND a +12 V DC as GND then you add the additional +12 V DC it produces on it's own when powered on. To utillize the +24V DC you've created between the PSU you need to use PSU A GND wire  and PSU B +12V DC wire in operation and between those to wire to be more excact theres +24V DC @ the amperes that one would have given.

I also slashed all wires i wouldn't use for this project to inhance airflow in the small cabinet i build. Again think twice cut once.

Step 2: Leach the Beast

Create a box and make it just as safe as you treassure your own life.

Hint: I'm refering to the danger of electrocution.

When you are working with tree, in my case MDF, make sure you dismantle the PSU from the mockup board. Before cutting and clean all pieces very good. Just to minimise the risk of a fire turned on by any sparks.

Since all PSU are different i had to make seperate on/off switches to PWR them on. First i PWR PSU A then PSU B. Before i put switches in it only sporadickly PWR both on and only gave +12V DC out because PSU A didn't function properly.

Step 3: Enjoy the New Tool.