Solar Charger

Etching Away

This is a continuation of my work with a solar-powered USB charger. See the last article here.

A few days ago, I tried etching the board. It's nearly the first time I've etched anything at home, and it didn't quite work. (Etching, FYI, is the process of masking a copper board, dissolving the exposed copper with a reactive salt, and then removing the mask to reveal a printed circuit board.) Although the traces were beautiful, the entire board was mirrored vertically.

PCB layout for the power regulator The first etch wasn't a complete waste of copper, though. I found that my inductor footprint was twice the size it should have been (diameter != radius) and that the regulator's feedback was mistakenly connected to the switching supply, rather than the stabilized voltage by the capacitor. With that in mind, I trashed my original revision of the printed board and drafted one half the size. (The original had a lot of empty space.) I'm going to try etching again later today.


All of my parts, arrayed across the table.
So much electronic loot.

For years (and years), I've dreamed of making a little solar charger. You know, some little gizmo with a solar cell on one side, USB power on the other, and magic in the middle. That's always been the trouble, though: until recently, I didn't know enough magic electrical engineering to design one.

Now that I do, I'm a little surprised by how little the hard parts aligned with the parts I thought would be tough. The first time that I thought about this, back in high school, I was concerned about charging batteries. Everything else, I thought, would work off-the-shelf. Charging itself is the simplest part of the design.

So what was difficult? I'll get there. First, I want to talk about the parts I used and the design process.