January 14, 2012
There is not much to document in this project. I built a Joule Thief....who didn't ;-)
Mine is powered by a LR44 button cell (1.5V) and it light up a white LED which usually needs a minimum of 3.3 voltes to light up.
I just built it to test how long the LED can light with this one battery (it might be interesting for throwies).
Will update the blog when the battery is completely depleted.
Power on time: January 14, 2012, 3:30PM
DIY coil, double side tape to attach the battery.
Transistor soldered directly on the battery to make the whole thing a bit stable.
I am not posting the schematics here since everything is already available in the famous internet but if you want to know why this is working then I recommend this http://en.wikipedia.org/wiki/Joule_thief
Test failed. After 3 hours the battery was depleted. I don't know why it happens but have to check the windings on the ferrite core...maybe have to put more on...
The circuit is working good. It lit up a white LED with a tiny solar panel by 0.45 volts but failed in the long run with the button cell.
UPDATE Jan. 30:
Strange things happend. After the button cell died i attached the JT to a almost full AA battery and it was working for a whole week with full brightness. Then the LED faded away to a weak glow until it went off. This was just before I left for my holidays on Jan. 21. Now I am back home and the JT was still lying dead in my book shelf. Last night I saw it lit up again...wondering what happend. Then after about one minute the LED faded away, went off and after another 5 minutes it lit again. The brightness to the beginnuing was about 50%.
It seems that battery is recovering again and again but how long it will last? More to discover ...