Normal desktop computer ATX power supplies are freely available and in-expensive. They offer most of the popular voltages a DIY (Do it Yourself) or Hobbyist normally require for a bench-top power supply.
So what do you need?
Well, you need an ATX power supply like the one I used (shown in figure 1). You will also need some connectors and an ON/OFF switch (if your ATX Power Supply does not have a dedicated ON/OFF switch already), see figure 2. And lastly you will also need some higher gauge DC wiring, or you can also bundle all the existing wiring for a specific voltage and current (amp) output together. I did consider using the existing harness, but in the model of ATX power supply I am using, there just is not that much space, so I opted to rather replace multiple wires with one high-gauge wire. I also had a concern on how to get the whole bundle of wires into a lug of sorts so that I can connect it to the plug.
The specific ATX power supply I am using, has a 32A @ +5V, 0.6A @ -5V, 12A @ +12V, 0.8A @ -12V and 26A @ +3.3V. So I opted to use 4 Gauge High Current Power Cable that is rated to 25A, but then to run two cables on the +5V, +12V, +3,3V and GND connections – so that leaves me with quite a bit of headroom in the cable capacity (we do not want to create any fires by overloading under-dimensioned internal cables).
Figure 2: DC Wire
To access the different voltages, I bought some panel mount (4mm) Banana sockets in different colours from Jaycar Electronics. We also need an “On/Off” switch (see figure 3).
Figure 3: Bannana plugs, recepticals and an ON/OFF button
Next up, is to replace the existing wiring with the higher spec DC cables we talked about earlier (shown in figure 2). As I mentioned, you can also bundle all the existing wiring for a specific voltage output together, but it is really difficult to get them all into a lug so that you can make a good quality connection between the wiring and the Banana sockets.
Figure 5: Standard wiring harness for an ATX Power Supply
Desolder all the existing wiring, and then drill bigger holes for the higher gauge DC cables to be connected to the PCB (Printed Circuit Board) – see figure 6, 7 and 8.
Figure 6: Removing the original wiring harness
Figure 7: Adapting the PCB for the thicker DC wiring
Figure 8: Heavy duty DC wiring installed
All that is left, is to install all the Banana sockets. Connect all the DC cabling to the Banana sockets. Install the On/Off switch.
The last connection that you need to do, is to find the Green wire and connect this to one of the terminals of your On/Off switch, and the other terminal of the On/Off switch gets connected to GND. So, if you flip the switch, then the Green wire will be connected to GND. You will see that most ATX power supplies has a feedback connection that need to either be connected to GND or to have a small load on one of its circuits (e.g. the +5V) before it will start to deliver an output. In my case, the power switch will connect the Green wire (“PC on”) to GND, and then the output voltages will be active.
That is it! Some final comments:
- Get the specifications for the power supply you intend to convert, and make sure you understand YOUR specific device.
- Do not under dimension cables, wires and plugs – safety first!
- Make sure that your Power Supply, supply cable is plugged into a wall plug that is earthed. If not, then you might see all sorts of drifting on the voltage outputs.
- Enjoy and congratulations – you now have a really good power supply for all your work-bench/hobby projects.