THE DEVIL SUGGESTS
Build a solar USB charger
Put together a small solar-powered USB charging setup for learning, camping preparation or emergency kit experiments. Use purpose-made USB power-regulation parts rather than connecting a panel directly to a phone.

Do it
- Choose a solar panel, battery pack and regulated USB output module.
- Check that the components have compatible voltage ranges.
- Connect and test the charging circuit in bright daylight.
- Put the parts in a weather-protected enclosure.
- Test it first with a low-value USB device or meter.
What next?
Keep the useful notes, photograph the result if there is one, then go and find something else to do.