I've wanted a variable mains-powered power supply for a while, so when I found this kit for a reasonable price I decided to give it a go. Some things that attracted me:

• 220V/110V mains-powered
• continuously adjustable output voltage
• isolated output
• nice acrylic case
• built-in LED voltmeter

The kit and PCB comes with a few "valued-added features" unrelated to the power supply function (CD4069 square-wave generator, externally-triggered piezo buzzer, externally-triggered polarity tester), but I decided to leave those out of the build.

I also enjoyed investigating and old-school transformer-based power supply. These are getting rare .. it's hard to even find a 220/12 transformer for less than the price of the kit these days, and then they are mostly used/refurbished.

How does it perform? Nice! No smoke on power-up, but a few things to note and/or improve. And I'm sure it wouldn't pass a safety certification, so don't go building one like this for friends.

As always, all notes, schematics and code are in the Little Arduino Projects repo on GitHub.