21 Feb 2006, 16:21
I dont own one of these water watches, BUT isnt this likely to be somesort of bi metal electolytic reaction giving just enough volts (but no current) to drive the LCD module ??
EG, get a 2 zinc nails or similar, 2 copper coins, insert them into 2 lemons, and joing them all up, and you will get 1.8volts all day long.
Same type of reaction can be made with potatos and other fruits. Even milk, salty water, ionised water etc all works. You can experiment with loads of different household objects and ligquids just so long as the two metal electrodes are different metals.
As for the water watch, it looks like it might have a tiny bank of 3 water based electrolytic cells making 1.5 to 2 volts when wet. LCDs only need 5-10 microamps which is no problem.