While browsing through his local dollar store, [Taylor] came across a suspicious looking rock that, upon closer inspection, turned out to be a solar garden light. He scooped it up, took it home and cracked it open, modding it to function as a handheld solar flashlight.
Inside was a pathetically small 40mAh rechargeable battery, which he upgraded to a more standard rechargeable AA. The garden rock came pre-built with its own boost converter to kick up the voltage for the LED, but it was fairly dim. We’re guessing [Taylor] didn’t bother reverse engineering the converter and instead simply did some trial and error, but he managed to increase the LED’s brightness by slapping on a different value inductor.
As fun as it may be to have a rock for a flashlight, [Taylor] decided to cobble together a custom case out of a spare USB charger, making a battery holder and adding a pushbutton. The result is a handy solar flashlight that takes around five hours to charge. Check out some other custom lights: a lithium-powered PVC flashlight or one with a snazzier aluminum body and interchangeable heads.
I bought a couple of these solar rocks and made an ultraviolet neon note board. I also looked at the joule thief circuit with interest. Video and writeup at: http://www.observationsblog.com/4/post/2012/05/ultraviolet-leds-and-solar-fun.html
Pretty good buy for $1.00!
Wow, wtf they didn’t even use a AA battery? how cheap can you get.
When you’re selling something for a dollar pretty cheap.
I don’t particularly care for this mod, but I too have stocked up on 15+ panels similar to this (the “patio/sidewalk light up solar ones also at those same thrify stores) just cuz they were a buck each. Had visions of series/parallel’ing the panels up to be more useful – Never thought of dropping a bigger battery (mah-wise that is) and using an inductor on them, though.. Still not sure what I want to do with them, though just yet :(