WORKSHOP VIDEO #27: ATX Breakout Board

Old ATX computer power supplies are cheap-to-free, and make great lab supplies if you’re willing to add a resistor and short a few wires. Sjaak whipped up an ATX breakout board as an easier way tap and control an ATX supply without any messy hacks.

3.3, 5, 12, and -12 volts are routed from the ATX connector to screw terminals on the breakout board. Each rail has a 1.25 amp resettable polyfuse to protect projects from the full 30amps+ some power supplies output. This workshop video is about the breakout design and features.

  • -12, 3.3, 5, 12 volt supplies @ 1.25 amp
  • 1.25 amp polyfuses with reset on each power rail
  • Indicator LEDs show that each rail is working
  • Power good and enabled indicator LEDs
  • On-Off button and control circuit
  • Optional load resistor included but NOT soldered
  • Open source (CC BY-SA)

Available for $13.80 at Seeed Studio.

Join the Conversation


  1. On all the ATX PSU that I used, none needed the load, but Without the load resistor, most of the times the value of voltages are a little bit off, most of the times the 12V rail are the worst, sometimes not even get 10V, but with the load no problem.

    Also for some, the load should be at 12V rail not on the 5V, a mess I know.

  2. I forgot to say, that many times with the resistor load, the voltage noise are quite smaller.

    But, exist many ATX PSU and almost every one are a bit different.

  3. Sorry for commenting here about the SoB, but I couldn’t find a comment field on its page.

    Can you add a credit card size (85 x 56mm) to the golden rectangle options please.

  4. Ian, thanks for the nice video and project board. I will pick one from Seeed Studio. I was hesitant for the reason that these monsters could supply a huge amount of current. But, your polyfuse idea is wonderful.

    For some projects we may have a need to supply more than the 1.25 amp, So I think a jumper or switch in parallel with the polyfuse could be helpful. Something like safety or Current Limit ON/OFF.

    Any plans to include a small area that could help bring out an adjustable voltage pin with a linear/switching regulator in place. You need not populate this area, just the footprint it itself would be very useful. Just like the load resistor and the negative 5V provision you have already made.

    Also I was not clear about the second un-populated ground seen as part of the board. Is it just a spare or does it have any special meaning?

    And Ian, nice hair do. :) And you have to teach us how to talk while smiling all the time. My 5 year old daughter always asks me how come Ian is happy at work and I am grumpy while working. Thanks I learned something new today. Keep up the good work.

    1. Hi Raja,

      I’m glad you like the board. I’m also reticent to work with the 30A+ on the rail of some PSUs and the fuses are a must.

      Good idea on the jumpers. I think the trick would be a switch that can handle the extra current at a reasonable price and board footprint.

      An idea for a future version is indeed to have an adjustable positive and negative voltage regulator, board space allowing.

      The second ground is just a handy extra. If you want, you can pop a terminal on there for an extra spare ground.

      It’s laugh or cry, I’m afraid :) I always set out to have a conversation and edit it down, but in reality there’s certain points I want to hit and I end up doing 20-30 takes of some bits to get them all. I smile bigger to mask the anger :) I really hope to get better with practice, but after 6months+ it’s still a bit wooden. It’s a lot easier to do the on-site stuff because you really do have a conversation with someone or at least a camera person. In the workshop it’s usually just me talking to myself.

  5. I was thinking about how some projects I work with use far more than 1.25A, especially on the 12+ so I downloaded the eagle files and added 0.1″ spaced jumpers in parallel with the fuses. :)

    … and then I came on here and found that someone also had the same idea.

    I’m bouncing over to Seeed’s Fusion PCB to have a run of the modded boards made, then Digikey the parts (blue LEDs thank you very much!) and I am contemplating changing them to a slightly larger size to make soldering a little easier. I have been thinking about doing this sort of break out board for a while, especially after shorting out my last modded PSU (had a nice face panel and everything… wire clipping fell inside the vent slots). This is great. Money coming Seeed’s way!

  6. Thanks for the excellent ATX Breakout board , cost about $20 Au and I bought a good 400w PS new for $40 Au , folded a tray with a facia to mount the breakout sprayed everything (except the breakout)
    satin black , goes good and looks awesome.
    Rod Watson W.Australia

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