Strange things are afoot inside my Sapphire 25.

[fyrstormer]

I have a modified Arc AAA Ti using a special 5-die LED, and tonight I decided to test it to see how many mA it was pulling. The readout was around 150mA, which sounded about right for that LED. Then I decided to test my Sapphire 25, and much to my surprise it was using 140mA!

The way I tested was: I touched the red probe to the + terminal of the battery inside the battery tube, and I touched the black probe to the + contact on the back of the head, and I touched the head to the battery tube to complete the circuit. Is something unexpected happening here, or am I doing the test wrong?

 

[McGizmo]

From the bench testing I have done, that sounds pretty high in current but what is the voltage to the LE when it is pulling 140 mA? I wonder if you have some high resistance in your makeshift circuit there? :shrug:

With my bench supply set at 1.1 V, I usually see 80 - 110 mA being pulled by the LE. I put the + probe against the + on the back of the PCB and push it in towards the head and I put the - probe on the side of the head.

 

[fyrstormer]

Well, when I run the same test using the voltmeter function, it reads out at 1.2V. It's worth noting that not enough current can make it through the voltmeter to light the emitter, though.

When I test the resistance of the interface between the head and battery tube pressed together, it reads out at .2Ω, which seems to be the lowest readout above zero that my multimeter can give me.

It is possible I just don't know what I'm looking at; the way I figured it, if the driver is running the emitter at 3.4V x .025A = .085W, that translates to 1.2V x .071A coming from the battery, or let's say .079A assuming the driver is only 90% efficient. But I guess I don't really know how efficient the driver is, so beyond compensating for the lower input voltage I'm basically pulling numbers out of my...uh...hat.