need some resistance

[p moore]

I just put all the pieces for my P7 M@G C togther. I got the emitter from Fred at Photon fanatic. I turned it on and WOW! However, I noticed a little color shift. I quickly turned it off. Then checked the amp draw at the tail cap. I quit when it went over 3 ampsdidn't want to push it.

Two questions. What size resistor do you guys recomend? and can I add it to the tail cap, or do I have to disassemble the whole thing. I would like to run around 2.5 amps.

Thanks, Paul

 

[Al Combs]

I used a 0.1 ohm 5 watt power resistor that I Arctic Silver epoxied onto the back of the heat sink. It was an "I" binned emitter. I was getting over 3 amps initially without the resistor. Fresh off the charger now I get about 2.7 amps. I think it would be more work trying to isolate the tailcap spring than it would be to take the head apart and put a resistor there.

I took a voltage reading from a power supply at that was cranked up to read 2.8 amps. Then I put a 1 ohm 10 watt resistor directly across my 3*NiMH 10,000 mAh D cells to see the approximate output voltage of the batteries under load. Then I did an Ohms law thing to calculate the value of resistor needed to bleed away the excess voltage. And promptly came up with the wrong answer. It was trial and error for me. I had a bunch of power resistors lying around to figure out which one I needed.

Also when I was setting it up, I bridged the resistor with a bare wire clip just to see. There was a barely perceptible increase in output without the resistor. Even if you have an I bin emitter, yours might be slightly different than mine.

I'm sure you know this already, but a good constant current regulator is much better than a resistor. More money than a resistor, but cheaper than a new LED. They just didn't exist a year ago when I built mine. I don't know if TaskLED's hipCC will fit in a C MagLite. The board is 1.1" across. The Shoppe's Shark Buck will and they even make heat sinks for the C MagLite.

 

[p moore]

I do have some of the DX 7882 boards comming. I was hoping for a simple fix today. Patients is not one of my virtues.

Does anyone have a couple of the AMC7135 1400mA Regulated Circuit Boards they could sale. I don't need a 20 pack when ever they come off back order.