On 9 April 2015 at 00:32, David VanHorn wrote: > It does seem that "charge your Iphone" is the magic phrase for these > projects. > Perhaps some sort of perpetual motion gizmo with a USB port would work? > If you use up a battery in 1 day (about 7.5 Wh) then say 10 Wh will be enough to charge it. If you have an activity with constant or substantial motion that should be doable. For 1 2 3 4 ... 8 hours input that's 10 5 3.3 2.5 2 ... 1.25 Watts average input. Outdoors in a sunny clime you may get by with about 2W of PV panel with MPPT. Top of hat mounting would be good. May not suit some :-). 10 Wh =3D 36000 Joule. For 1000 2000 4000 8000 steps that's about 36 18 9 4.5 J/step. Total energy in a typical step is maybe 80J (deepending on your mass and whether you are walking jogging or goose stepping) 36J is too much to hope for. 18 is a bit steep probably 9 or less sounds doable with due care. Say 10 W.s =3D 1 kg.m delivered per step over 4000 steps. .... > PT Barnum had it right.. Indeed - you can definitely get some of the people to buy iPhones all of the time. Russell --=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 .