# Gravity powered Light

Design Crime, or… … another shameless plug for funding?

Neither, I think.

I thought this was going to be the perpetual motion lamp that won the greener gadgets competition a few years ago.

This one at least has physics that are a bit more sound, but that design didn’t look like anything that could be built for \$10

Either way, if they manage to design something that actually works, they’ll still need to overcome the massive distribution challenges with Africa, but it’s definitely a worthwhile project that lots of groups are trying to tackle so I hope they succeed.

The math on this is easy. Take some reasonable values for what an average person can lift, let’s say 10kg lifted 2 meters high. In that case your maximum potential energy (mass * gravity * height) would be 196 joules (you can’t convert it all to useful work, so in practice it will be less). Joules = Watts * seconds. The first low power LED I googled uses about .15 watts, so you’d get a maximum of 22 minutes of light. That’s close enough to what they are claiming. It would be a pretty simple circuit, I don’t see any reason they couldn’t make it in volume for \$10.

I really like it, the video delivery suits it, especially like how the project changed from “this is what we were asked to do” into something better. My only concern would be if it fell - hanging from the ceiling with a weight attached, and the force required to set the weight, how sturdy is it if it rips out of the ceiling and hits the floor, and how easily it could be repaired.

Pretty smart. Similar I suppose how a grandfather clock works with hanging counterweights. I think you only need to pull the weights on a clock once a week. If they made two bags of weights like a clock and let them slowly drop you could see when you need to charge it and the lamp would stay in one place. Might be even more efficient.

R