D.I.Y. Illuminated tailcap

I’m baffled, but now that I think about it the double blue tailcap is pretty dim too (although it’s running a 4.7 or 6.8k limiting resistor). I may bump that to a 220, build a single in blue and a single in red at 2.2k and compare them all.

I can’t fathom why the single might be brighter, but the single I built in green with a 2.2k is BRIGHT.

I’ll be interested to hear what you find.

So far I have done 2 red doubles, 1 red single, 1 green single, and 1 blue double all with the 0805 led’s from lighthouse. On all of them, I have had 560ohm on the driver and 2.2k-6.8k on the tail.

Not something I’d normally consider, but do they carry a low output version of this LED and I just got the wrong one shipped to me?

With the fact that I’m getting a measurement of 5.7mA it’s hard to imagine that they’re having a problem with getting enough power.

No i don’t think they do. I’m more inclined to think we have something stealing current somewhere. Where are you measuring the draw?

I’m putting my DMM in line with the negative battery terminal to brass button and a jumper between the body and tailcap ground.

Keep in mind that driving it from my power supply doesn’t increase brightness, so I don’t think it’s driver related.

I’m staring at your pictures and don’t see anything wrong. I have gotten a board from osh with an internal short one time, but only one out of the batch was like that.

Any way to measure the draw at one of the led’s to confirm how much they’re getting? Is it possible they could have gotten overheated during assembly? (unlikely since we’re talking about 4 different emtters)

Just spit-balling here.

That’s a tall order, but I’m committed to the cause and I have some pretty pointy leads so I think I can make that happen. I’m about to get the boy from school though, so further progress will be on hold till later tonight.

So, when powered from the spring side, dim. Power applied to switch side, bright. I think it’s the damn boards.

Well at least that would explain a lot. Just looking at the boards, are the via’s all present and accounted for?

I think so. Should I try filling them with solder?

I’d check for continuity/shorts first. Its drawing a lot from the battery, so that power has to be going somewhere

Running off of a power supply after filling the vias:

Powered completely by spring side, dim
Negative on spring, positive directly to LED, dim
Positive to outer ring of spring side, negative to LED, BRIGHT!

So a problem between spring pad and back side then.

Nope, even when powering the negative switch contact it’s dim. I’m going to try to jumper from there to the negative pad on the resistor.

Well the negative goes through the resistor, so if you’re connecting power directly to the led- pad, you’re bypassing the resistor.

Maybe there’s a problem with the trace leading from the r1 to d1

I’m starting to question the theory. I think I was just bypassing the resistor on the board hooking it up that way. I tried one directly on the power supply @ 1mA compared to 2 directly across the LED’s and they were similar, through the resistor the ones on the board got a lot dimmer. I need a break for an hour, it’s driving me crazy.

I built 2 of these using a single 3mm rgb led i pulled from an rc helicopter. One for a DD and one for a 105c, neither one needed the resistor on the driver or had any change in the memory function. I tried the resistor on the BLF DD and that caused the mode memory to fail. I am just using the standard switch pcb with a resistor in series with the led. So its wired like this: spring pad - resistor - led - outer ring. the spring side is the - connection for the led.

So after some sleep I’m back to troubleshooting. I’ve got another board with all the vias filled with solder, and tested the resistance of every part of the circuit path and everything is fine with the board as far as I can tell. I’m going to put 2 greens on it at 1k and compare to the 2 red 1k brightness. Pictures soon.

I think all this troubleshooting can finally be done. The red LED’s simply aren’t as bright as the green (and possibly others). The green LED’s are pulling 1.8mA in this picture using a 1k resistor. The reds are pulling 2.4mA using a 1k(difference due to forward voltage I believe). The green is obviously significantly brighter on less current.