The postman brought me a package today and I opened it up. I was surprised to find the thing I’ve been waiting for for almost a year. It’s a potential to kinetic energy converter – the Gravity Light. I got to work and assembled it and hung it from the eaves outside. I filled the small bag with a pint glass jar of water, about one and a half pounds or .7 kilograms. I filled the large bag with stones, about 21 pounds or 9.5 kilograms.
I measured the top of the unit’s hook loop at seven feet 9 inches or 2.36 meters above the ground. This is about typical for a home installation. I pulled the small bag to the ground and timed the run time at 16 minutes 45 seconds. That’s pretty good.
I waited until dark to see how bright it was but it’s a full moon out tonight and that’s not the most ideal conditions. I wouldn’t want to read under it unless I was within a few feet, but that’s not possible as long as it’s hanging high up above.
The large bag is long and touches the ground too soon. I think that if the bag was shorter and wider it would probably run for another minute. Also I could raise the unit a few inches and that would make it run several tens of seconds longer.
But it’s working good so I shouldn’t complain. There is enough slotted strap to give 20 minutes of runtime. It’s just that the limiting factor is how high the unit can be mounted to give maximum run time.
Their website is www.deciwatt.org. I went to the website and watched the video. On the assembly sheet there is no explanation for the 3-position switch labeled I, II, and III. The video showed that the three position switch controls the brightness of the LED. It comes set to the second position. This is the position that I used when I did the runtime measurements.
Here’s a bit of technical information. Stones or rocks and similar stuff from the earth have a density of two and a half to 3 times that of water. I used stones to fill the heavy bag up. The stones took up the whole bag with no room left. A piece of iron or steel has a density of 7 to 8 times that of water. That’s more than twice as dense as rock so it would take up less than half of the heavy bag. Many developing countries have scrap metal for free. By using A 12 kilogram piece of iron or steel, it could be much smaller and shorter then the bag. This should give the strap another 30 centimeters or one foot to travel and hence allow the run time to be increased by as much as a minute before it touches the ground.
I’m not being critical to put the products in a bad light, I’m just trying to add some information that I hope will be useful later. One reason I am giving this critique is because they asked for things to add or change in their Mark II model. I’m going to give them a link to my blog so they can read it.
Glad to hear you finally got your gravity light. Does it only power a LED when working or does it also charge a battery?
It comes with a standard 5.5mm power jack. They included a plug which has two screw terminals on the other end where you can connect anything up to it. But when it’s plugged in, it shuts off the internal LED. So it’s either one but not both. You have to finagle with it externally and add the LED and whatever else you want. Power the Eiffel Tower with it if you want. You just have to charge up a bank of supercapacitors for a week (or more) and hope there’s enough juice to light le Tour Eiffel for a short period of time. 😉 Ooh-la-la!