Surefire 6P -> Luxeon lamp assembly

Coherence

Newly Enlightened
Joined
Mar 7, 2001
Messages
130
Location
Bend, Oregon
I made a replacement lamp assembly for the 6P. It consists of the LS w/optics, a piece of aluminum tube, 2 steel and 2 rubber washers, and a nut and bolt. And a bunch of heat conducting epoxy, plus resistors.

It is running at 480mA with fresh batteries, and about 140 mA on cells that will just barely light the P60 lamp.

On new cells it puts out more light than the E1, but much whiter. The E1 is tightly spotted though, and has a farther reach.

Heat sinking - I ran it for an hour, wrapped inside a cloth towel. In the end the whole light was warm, I would say about 95 deg. The lamp assembly was the same temperature.

Efficiency - I'll do the math:

I settled on two 2.2 ohm (1 watt) resistors in series = 4.4 ohms

The following is for the efficiency LOST by the resistors:

V = voltage
w = watts
I = current

This is a series circuit so I = 480mA = 0.48A through every component (with fresh batteries).

The voltage drop across the resistors I * R = 0.48 A * 4.4ohm = 2.1v

So 2.1v @ 480 mA is wasted by the resistors, as heat. The power lost is I^2 * R = (0.48A)^2 * 4.4ohm = 1.0 watt.

The whole circuit is consuming power = V * A = 6v * 0.48A = 2.88 watts (actually a bit less, as V is less than 6v as the battery sags under the load).

So the efficiency = power out / power in = (2.88w - 1.0w) / 2.88w = 0.65 = 65%. Not exactly stellar performance.

But remember that is only when it is running bright. At 140mA only 0.62v is dropped by the resistors and 0.09 watts is wasted. As the current gets smaller, the circuit gets (much) more efficient (as a result of the I^2 term).

If I made any math/theory errors someone please correct me.

Drawing 500 mA on 1400mAh cells the batts would last 1400mAh / 500mA = 2.8 hours. That's if the voltage doesn't change, which it does. Anyway, figure a couple hours bright and then diminishing light that lasts a long time (days).

Installed in the 6P it is very solid, I wonder how much abuse it would take to make it fail?
 

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