Somewhat DIY Variable Power Supply

Making a variable power supply out of a laptop adapter and a step-down module

I needed a simple variable power supply for testing and prototyping various projects. I started looking at buying one, then started looking at DIY kits for making one. I had a few of these step-down modules with a voltmeter display, and an old laptop adapter from a broken laptop. I figured I could put them together and it did indeed work.

I didn't really have a proper way to open the laptop adapter. I tried prying it open but failed. I ended up carefully drilling holes around to open it.

I de-soldered the existing power cable and replaced it with my own pair of wires to run to the step-down module. I have the wires soldered to opposite sides of the board since it was a bit of a tight place to solder, and I didn't want to ruin anything nearby with the iron.

The step-down module came with a heat-sink and fasteners. I drilled holes into the top of the power adapter case and fastened the board down.

I put the power adapter back in the case and taped it all together as I couldn't find a better method. I fastened the wire coming out from the adapter into the IN side of the step-down module. As seen in the picture, it gets 19.3V in which is more than most of my project's needs.

The laptop power adapter is rated for 65W, 19V 3.42A. The step-down module is rated for 4-38V input and and 1.25-36V output up to 5A. I've been using this power supply for a few months and has worked for every project I've needed it.