29 November 2010

The Joule-Doh night light

What do you get if you take a joule-thief and put it inside a play-doh can? A yellow "Joule-Doh" light! (or a "Play-Thief" one?!)

Recently I have re-engineered my homebuilt joule-thief after a too heavy shake that broke one wire. It was a good chance to let my older daughter choose for a new container, and a new color.

An empty play-doh can laying around was chosen as the new night light. The lid holds just right a 1xAA container and a small SPST slide-switch. Wires hold up the LED.

The 5mm while LED gives a quite directional light beam, but the transparentish can allows the light to be diffused around.

The Joule-Doh night light generates enough brightness in a dark 4x5m room so that you can walk around without hitting abandoned toys and tuck your child(ren) up.

For those not familiar with the "Joule thief", it is an oscillating circuit that allows to light a LED out of a 1.5V battery (be it AA, AAA or button). It usually works down to 0.8V, so it is a very good way to drain all the juice from those batteries that won't work anymore in normal toys. This one has been running already for 5 nights off the same "officially discharged" AA battery.