Could use this in the States--we need the exercise. On Sun, Dec 8, 2013 at 4:56 AM, BOB wrote: > So where can I buy a couple of these. > > I can imagine some petrochemical company is going to try to block this > device so they can get those pennies from the poor people of the world. > > It is a fantastic idea tho. > > Bob > On 12/8/2013 3:57 AM, RussellMc wrote: > > Much talk hither and yon about a year ago re a "gravity powered light" > and > > it's likely capabilities and chances of getting to market. > > > > They reportedly have got to a alpha or beta release candidate version > (not > > what they call it). > > > > > http://www.theregister.co.uk/2013/12/05/gravitylight_rolls_into_productio= n/ > > > > Home page: http://deciwatt.org/ > > > > As the name implies, output is nominally 100mW. > > > > The Register article says: > > > > Well, the initial GravityLight was just a prototype - it wouldn't hoist > > more than 10kg, and it wasn't really safe to use. It broke easily. The > team > > has also made it more compliant with safety regulations - and it now > gives > > unmissable visual feedback if it's overloaded or tugged, by flashing re= d. > > Bearings were stripped out, and it's now a robust piece of kit, capable > of > > holding 7.5kg to 12.5kg of weight. And it now contains gears - so you c= an > > run an LED for 30 minutes at lower power, or 15 minutes of higher power= , > > with an intermediate setting giving 22 minutes of light. > > > > Kits are going out to Guatemala, the Philippines and Bangladesh to gaug= e > > real user feedback. The proposition, Riddiford explained, is: do you wa= nt > > to save a few cents a day in fuel by lifting a weight? If people find > that > > acceptable, then it's likely to go to the next stage. The economics, > > Riddiford told us, are compelling. Each hoist saves about 1 cent's wort= h > of > > kerosene. Over two years this adds up to a saving of $100 - so the devi= ce > > pays for itself quite rapidly. > > > > Their $100 saved in 2 years figure infers 15 reloads/day and a break ev= en > > time of under 3 months at a market cost of $10. > > > > A figure of 100 mW output at full power is mentioned. > > Elsewhere they say 2m (about) lift, 12.5 kg max load, and 15 minutes at > > high power. > > The mass x head gives 250 Watt second of input energy. > > 15 minutes at 100 mW is 90 Ws of LED power for an efficiency of potenti= al > > energy to LED input of about 35%. > > If they in fact achieve that overall it's a very creditable result. > > > > 100 mW at 150 lumen/Watt (which hopefully they will equal or exceed) = =3D 15 > > lumen =3D useful. One person can read a newspaper page (say A2) at a > > comfortable level with 15 lumens. (Evenly distributed that would give 6= 0 > > lux which is low by Western standards but enough for comfortable colour > > rendition). Real distribution will not be wholly even, but 15 lumen is > > still very useful. > > > > One of these could power a light in an otherwise unpowered washroom or > > toilet cubicle, with a single pull giving 15 minutes of lighting. > > (A useful addition to any remaining "pull the chain" toilets of > yesteryear. > > > > Make a ratchet device powered by walking on a step and small increments > > could be added as each person passes a point. > > A 10mm fall in a step would probably be unnoticed and a larger fall if > > known of would be acceptable when walking down stairs. > > 10mm gives about 5 seconds of full output and 100mm gives 50 seconds. > > > > A children's swing game that uses descent energy could provide many > > recharges per minute. > > (An idea I included in a proposal for a developing country charging > system > > proposal some years before DeciWatt surfaced - it was not accepted). > > > > > > At say 25% overall, energy ~=3D > > meters_fall x kg x 10 m/s/s x 25% W.s (=3D Joule) > > =3D 2.5 x m x kg > > > > [The idea is far from new - some early 20th century homes were lit by > > gravity powered electric lighting with weights in the ton range and > > servants using suitably geared winches to raise the weight. ] > > > > > > > > Russell > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .