E2 conversion -> led low/high power

I made Brad's LED conversion, then took it apart and reassembled adding a switch and a resistor so you can have high and low brightness.

More detail: the switch is a DIP 4-pin (has two switches on it, I am just using one), got it at Fry's for $1.50 or so. There is a 33 ohms resistor in series with the led, current is 70ma at 6v.

The switch is wired across (parallel with) a 3000+- ohm resistor, in the on position it just shorts out the resistor, off position gives 6 volts / (3000 + 33 ohm) = 2 ma.

High brightness time = Surefire lamp = 75 minutes

Medium brightness time = 1400maH / 70ma = ~20 hours

Low brightness = 1400 / 2 = 700 hours = ~1 month

At low brightness it is still brighter than moonlight, because I can see colors with it.

So now I have what I have wanted, low/medium/high in a small and sturdy package. Of course there is the major problem of having to disassemble/reassemble it to change brightness...

Well, we get closer to the ideal light every day. Gotta love that E2. I took off the pocket clip, tried to scratch the finish underneath with a steel key, just tiny bits of key left on the light afterward.

Side note: you can put the module in an E1 as well.

How about ditching the resistor(s) and using a 50 Ohm potentiometer instead?

Initially, it is set to 30 - 40 Ohms, so the LED is bright, but within the safe limits.

As the battery voltage drops, and the LED is too dim even though the battery has lots of juice left, the resistance is readjusted so that the LED is nice and bright again.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>How about ditching the resistor(s) and using a 50 Ohm potentiometer instead?
Initially, it is set to 30 - 40 Ohms, so the LED is bright, but within the safe limits.

As the battery voltage drops, and the LED is too dim even though the battery has lots of juice left, the resistance is readjusted so that the LED is nice and bright again.<HR></BLOCKQUOTE>

Nice idea, I actually have a 200 ohm adjustable but I was thinking that there would be too many problems with it because:

1. mine requires a tool to adjust it.

2. replacing battery may damage the LED.

3. no way to determine how bright it will be until you reassemble it, so it is disassemble/adjust/reassemble cyle.

4. Lithium cells tend to provide an almost constant voltage until they are about depleted, so they should not need a lot of adjustment. Alkaline cells are a different matter of course.

What would be great is that the tailcap push button is high power, and rotate the tailcap from off to medium on the LED.

can anyone figure out a way to do that?

Coherence, I agree with your reasons about not using the potentiometer. I better stick to a regular resistor in my upcoming P60 mod.

Your proposition about rotating tailcap is theoretically possible, but I don't think it can be accomplished without modifying the tailcap (which I don't think is a good idea).

Another reason against using a pot is that most are carbon-based, and rated for VERY low currents - typically microamp levels found in the front-end of audio equipment or test instrumentation. With an LED pulling as high as 80-90mA on a couple of 123's, the pot would fry in no time - probably making a detectable, somewhat unpleasant odor in the process. (Peeeee-YOU!!!)

Using a wirewound would eliminate this problem, but you might not get enough resistance on the high end to make much of a difference.

$0.02

I thought lithium batteries had a large voltage fluctuation over charge cycle- or are there different "recipes"?
Chet

Actually, 123 cells have very flat discharge profile, which makes it particulary useful for LED lights not utilizing step-up/down circuits.

DL123 discharge profile:


MN1500 (Duracell "AA") discharge profile: