Tuesday, April 29, 2008

Joule Thief Artbots


A popular circuit for electronic hobbyists called a "Joule Thief" has been making the rounds on the Internet.
When your batteries go dead, there is still energy or "joules" still left in that battery. Instead of simply tossing it out to get recycled, why not squeeze out the remaning joules of life to do something useful.

With the Joule Thief circuit you can light a white led till the battery is down to .2 volts. Use it for a night light, it will run for days. Then, when it is good and dead, give it to the trash collector to get recycled.

2/10 volt and the led is still on!

The circuit consists of a ferrite core with a double winding, a transistor, resistor, led and the "dead" battery for power. Thats all there is. Sure you can put the parts on a perf board and make it work. I wanted more, so I built some artbots with the parts.


Ferrite uses a vintage germanium transistor to be able to run at very low voltages. Like all the way down to .2 volts.


Germanium also uses a vintage (1966) germanium transistor. This one is from General Electric. "Ge" is also the elemental name of germanium on the Periodic Table of Elements!

Here is a good modification you can do. Change the 1k resistor to something around 2.2k to 10k and place a CDS light sensitive resistor between the transistor base and emitter (or use a trimmer). This mod will make the circuit light sensitive and cause the circuit to shut down during the day. When its dark , the white led will light. Now how about that for a proper night light!

So go ahead and google "joule thief" and see what you can find, then make your own artbot.

Windsonics Album

I have received a lot of great response to my windharp music. I put together a group of my latest work at Soundclicks. Just go to http://www.soundclick.com/windsonics

You can download my "songs" or just listen to relaxing sounds created by the wind.