LED wiring questions?

[JavelinSST390]

Okay,

I scored four little LED flashlights at the dollar store for a buck each yesterday. They run on two little watch batteries each, are easily dis-assembled, and even better, some of them are ultra-brights!

Two of them are ultra-brite whites and two are reds. I wired 'em up to run two LED's in series, with four of the little watch-batteries to each pair. (four stacked together for each set of lights.) and the front two are so bright you can't stand to look directly at the thing.

My R/C truck now doubles as a killer flashlight!!!!

As Eric Cartman once said, "Sweeeeeeeeeet."


I just wonder if I have this right? The batteries say 3V on them, so am I running 12 volts through these things? That's too much for LED's, unless they're special made or saomething, (which I doubt, for a 1.00 flashlight.)

I tried hooking the ultra-brights to two AA batteries in series and got nothing, do I need 4? Or more with the four LED's? They just wouldn't even light up. Even worse, I have five more lights coming to go on this thing.

last night, I tried hooking all four of the LED's to one four-battery stack, in paralell (two LED's in series in each pair, hooked to the batteries in paralell) the strangest thing happened. The rear lights lit up, but the front ones didn't. I un-hooked the rear lights and the front ones lit up. Ok......

So what's wrong? Do I need more juice? I used heavier wire on the rears than the fronts, (I used what small wire I could find lying around, some of it was donated by the original drivetrain of the Gremlin body) Is the difference in resistance enough to be causing this?

So today i went and got a four AA-batery holder from radio shack (it's a neat flat arrangement that's enclosed and includes an on-off switch.)

I hooked that up to them and... What the? Now they're really dim. I went and got new batteries, so that's not the problem.

What gives? There aren't any resistors (that I can see) attached to the LED's... so what's up?

[Coligny]

Led going dark: felicitation, you smoked them. back to the dollard store for moaaaar.

White and red led plugged together, only the red goes on: they are spec'ed differently. (V/mA).

As long as you don't know anything about the characteristic of what you are using, stick to an equivalent setup as the factory one:
2 white in // with 1 of their power source (3 or 4 button cell) same, indep from the white for the red.

Also, don't replace button cell with AA or AAA. Button cells rated 1.5 give 1.45v while AA rated 1.5 give 1.7v this is often out of spec for cheap leds, they are really bright, then really dark... and sometime they catch fire... That's what happened to my bicycle last friday... Checked the batt... instead of 3x1.45v=4.35v i was feeding 3x1.7=5.1v way too much judging by the smokey result...

[Renslipevol]

Here's a neat little DIY project for running your LED's off of just 1 so called 'dead' 1.5 volt battery.

http://www.makezine.com/blog/archive...hief_made.html

And here's a great site I goto for LED circuits.

http://led.linear1.org/led.wiz

[Mr_Freeze]

Most of the super brights run off 6v. Like alarm lights in cars or the ones in computers most have resistors to knock down the 12v. But some run on less. Eg. the bright red flashing leds in bike lights... the common ones run on two AA bats. And ya... if they look brown or black inside and have a funky sweet smell... they are cooked.