I’m slowly working towards a project, it’s still not ready to be disclosed though, but it needed a dual rail power supply. I’ve always bought Doepfer DIY kits for my Eurorack needs, but I needed a +14V/-14V for this project. Since I could use an extra +12V/-12V supply as well for future Eurorack work, I decided to build a power supply with variable voltage regulators so it could handle both.
The main layout is simple. A power transformer which brings down 220V AC to 2x18V AC, put that through a bridge rectifier add some capacitors and put the result through 2 variable voltage regulators. Add a trimpot for the voltage regulator so you can finetune the voltage. Top off with some extra capacitors and you’re finished. I tossed a led in for a visual indication and added some fuses – safety is good mmmkay.
The ( LM317/LM337 ) combination can output anything between 1.2v to 37v according to the datasheets. They need a few volt of overhead, so that’s why I choose 18V. You don’t want the voltage being too high either to prevent the voltage regulators from heating up too much. So 18V to 14V seemed like a good plan. Nevertheless I provided some room in the pcb for cooling. You would be able to use this design for +12V/-12V applications or +15V/-15V applications as well.
disclaimer: This design features mains voltages which can be lethal, please take all necessary precautions. As always, double check your work, and mine. You should expect errors in my design.
- Adjust the trimmers until you reach the desired voltage output. A multi-turn trimmer will give you the precision you need.
- Make sure the capacitors used are the right voltage rating. 50V should be adequate but a 16V rating will actually explode.