Confused by a hack

Community General Discussions
1

Ahoy!

Not robot related again im afraid, but i like it here :p

I bought a flashlight (or torch this side of the pond) this weekend, 9 super bright LEDs, lovely milled aluminium body, 5 english pounds.

I cracked it open, expecting to find some circuitry of sorts, and all i found was 3 aaa batteries (4.5v, in reality more like 4.8v) and white LEDs in parrallel! why do these LEDs not fry? I can find info pages on "how to light an LED", and "how to do super copmplex stuff with LEDs" but nothing inbetween. Irritating.

i pressume this is what people refer to when they talk about voltage drop?

anyway, havign spent ALL day trying to hack a small "flashing" circuit into it, and failing miserabley, i have given up. I have replaced the 9 white LEDs with 8 super bright Reds, and a single white (i only had 8 reds) I think the White must draw less current, it barely lights at all, as far as i can see past the horrendously strong power of the 8 reds.

i measure just over 2.5v over the LEDs, and they run faiiiirly warm. (spec is 2.5 max, optimal 2.0v)

I want to use it as a tail light for my bicycle.

how long do you reckon they will last?

I think i will solder a piece of wire over one of the connections for now, and run 2 aaas, that still makes it blinginly bright, and the Voltage across a single LED is........2.2v

 

 

2

I have a similar problem!I

I have a similar problem!

I bought 5 red LEDs yesterday and i gave them approx 3.5 volts using a breadboard. All light perfectly but with somewhat less intensity. then i used 5 volts straight and then even 7.4 volts! at about 600mAh but the intensity was still same :0

3

Cool, thanks. I have taken

Cool, thanks. I have taken the White LED out now, as it was a bit pointless, and it is mad bright as it is. I will add a resistor somewhere though. should be easy enough to break a track on the cirguit board, and pop a resistor over it.

4

Oddbot, your tutorial is

Oddbot, your tutorial is exactly what have been looking for, nice one! that will be added to my “reference” bookmarks folder for sure!

I have been running the LEDs with two aas only, so that makes 3V, dropping the voltage across each to 2.2V. I blanked out the third LED, by soldering a wire in its place. I can just replace this wire with a 100 ohm resistor, which lowers it to a less ridiculous brightness.