At last I finished (2008.02) my torchlight project. I was looking quite a long time for good LED driver. When I found driver chip, I’ve lost all my white LEDs. So I used white LEDs from bad USB web cameras’. There are 4 LEDs in one web camera. I dissasembled several ones and collected 12 (in last edition 16) bright white LEDs.
Here is last PCB test before finishing assembly:
I compared light output using simple cheap incandescent bulb, but powered from one Liion battery. Bulb is 2.4V and 0.75A. As it was powered from 4…3.7V source, output power is much more. And it was very hot- plastic details near lamp melted.
|Variantas||Voltage, V||Current, A||Power, W||efficiency, %|
|12 x LED||3.5||0.4||1.4||41|
“Light power” comparison:
After comparing both types of the lamp I can definetely tell, that LEDs are better in case of energy use. But only if LEDs are connected using special driver chip. Cheap China torches are made without any driver and are not very good for advanced use. Looking from spent money, the situation may be different. LED driver chips and custom hardware is expensive. Another advantage using drivers chips is that light power is constant during all liftime of battery.
Final product: completely assembled light torch. It is made using aliuminium casing from China made torch. The original design of torch use two C size batteries. Now I am using two Liion acummulators from computer laptop battery. Total ~7.5…8V at 2Ah (15..16Wh). Theoretical non stop work time about 10 hours. In emergency situation (maybe with damage to Liion chemistry) the work time is much longer.
There was little problem with the size of battery- the idea was to place 4 batteries (2+2, 4Ah, ~28Wh), but they didn’t fit inside.