Via Slashdot, this is a terribly neat lamp.
I want more details so I can figure out the physics involved. We're given the height of the column, but not the weight of the mass sled, and there's two different figures for the running time (4 hours and 8 hours). Is that enough energy to generate the light output they state?
Some numbers: Single high output LED: 20 mA at ~5V (thus energy use of ~ .1W). They state there's about 10 high output LEDs, so that's 1W. This seems reasonable, as most LED light bulbs currently in use are about .9W or so at the low end. A 1 kg weight at a height of 1.2m (~4 ft) has about 12J of potential energy. That's nowhere near enough to power the LEDs for timescales of an hour. I'm clearly missing something for how this works, or my elementary physics is rusty.
Any ideas? Corrections to my physics are welcome, or other insight into how they can get it to work, etc. :)
5 comments:
I'm feeling too lousy to think about the physics, but I do want to comment that that is really fantastic. I want one!
Yeah, I don't see how this can work either. The diagram on the Greener Gadgets page shows that there are five weights of ten pounds each; lifting these 48 inches every four hours is an average input power of just 19 mW. I don't see a way around it: you simply need way more mechanical energy than this to produce 600 lumens for several hours.
You're right to be skeptical. The full comments on Boingboing have a pretty good breakdown of it, if you skim over the usual noise.
http://www.boingboing.net/2008/02/19/led-lamp-uses-grandf.html
I could really use fewer psychoceramics (like perpetual motion machines and cryptozoology) posts on Boingboing, it's nearly getting to the point of driving me away.
Sigh. I don't get why the Greener Gadgets people gave it an award, if it can't be actually made to work. It does give me more respect for how much energy it takes to even use high efficiency LED's to light up a place though. :)
It's too bad. It would have been really neat to have one. So much for wanting a cool thing for my apartment. It's fine for me to casually say I won't worry about the physics right now (thankfully without having purchased anything), but isn't the award it got (which is rather strange, as Z mentions) going to lead to people unwittingly buying them? That seems pretty damaging and makes me suspicious of shenanigans. (I might as well be very skeptical now after ignoring the physics last night.)
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