I love DIY and home-brewing. As an electronics engineer and hobbyist, the first equipment in my workbench is a stable, multi-voltages power supply. Formerly, I used wall-wart or small DIY power supply with mostly 78xx linear regulator. As for now, I think to build a workbench power supply.
There are many DIY workbench power supply designs around the net but I need a simple and stable for the first. Since I inspired by PC power supply base design, I started to build the one. Using power supply as power source is a good idea, no need to brother the design complex and quality plus low budget.
First, I find out good articles for reference.
Second, I find an old ATX PC power supply.
Then, strip apart all.
I find old 12V battery chassis. Good, this one has buildin switches, fuse and taps.
Measure, marking and drill holes for tappings. Install output taps.
Seat ATX power circuit, cut the cables and solder to each outlets.
The wiring diagram is as follows. I used 2 x 4.7 Ohm resistor with small heat sink as dummy load. Without it, the supply cannot be maintained stability.
The connection diagram is as follows. Interesting, my supply is labeled as -5V output (500 mA). I cannot find it in ATX pinouts. It (pin-20, white) is labeled as reserved in wiki page. After checking, this pin-20 is connected with a 5V zener diode is circuit. It is really a simple zener supply. Anyway, it is a good idea to put -5V pin-out although it is small ampere.
Oop! Don’t forget to connect fan power pins also. If not, your supply will heat it up. Note the original fans supply pins before take off. Usually, its a small red-black pairs cable.
Cover the case. I attached the fan at the right side and drill some holes for ventilation.
I removed label sticker from original ATX case and stick it over new supply. So, I can easily check the rating of each output. More, print out and stick labels for each taps. Finally, this is it. There is a new workbench power supply in my workbench. It is happily running now.