A rechargeable, battery-free LED torch which gets it's power from USB and stores it in a capacitor.
I reckon USB stuff is cool. I also reckon LED stuff is cool. I HATE paying for batteries. I love my shaky torch. Putting all this together, I thought I'd make a LED torch, simmilar in form to those keychain types, which stores it's power in a capacitor. The capacitor is charged from the USB port.
This is only a "proof of concept", and is intended to show it works. I doubt it will have the best performace, but that's not the point. I think I should be able to do it fairly cheaply, for about the cost of a keychain coin-cell LED light.
Step 1: Gather Parts
Obviously substitute parts and suppliers where applicable for your location. I think you can get pretty much everything here from SparkFun, but I listed Altronics as they are a good source for parts in Australia.
- 1 x 5.5V 1F Supercap - Altronics - $4.25
- 1 x 5mm Blue High Intensity LED - LSDiodes $0.75ish depending on exchange rate
- 1 x 18 Ohm resistor - DSE - $0.04
- 1 x mini push button toggle switch - SparkFun - $0.30ish
- 1 x Verobaord, 310mm x 95mm, 0.1" spacing - DSE - $7.99 - OK I didn't actually buy this, I used leftover scraps, but this is what you'd buy. You only need a small bit, so I'll count 1/10th of the price (even that's way too much)
So total is AU$6.13. Definately acheived goal.
Yes the capacitor looks like a coin-cell battery. Trust me, I'm not trying to cheat, that's what it looks like.