Is an illuminated tailcap possible?...... Solved?

Use gitd o rings on the body, gitd tail caps, glow powder mixed with epoxy filling a groove or a hole, tritium vials, a servant that holds your light for you. I like that last option best.

Why would it be necessary to run a wire from the positive side of the cells down to the switch?

Wouldn't the positive side of the led just connect to the flashlight body and the negative to the bottom of the cell? Any point in a circuit is a point where electrons are flowing. If the driver didn't have enough parasitic leakage, couldn't Pilotdog68 just connect the limiting resistor from some positive point in the driver to ground?

I have more GITD tailcaps than I could ever want, but they only glow for about 20 minutes after the lights go out, and not very brightly at all.

Again, the light in the tailcap isn’t neccessary, I just thought it would be cool if it could be done.

I really don’t want to modify the exterior of the lights.

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Anybody have input on post #9?

I like this train of thought, but would that affect performance of the driver in normal use?

I have used the glow paint. They have the one green rated longer than all the others and it lasts a long time. Depends on how thick it is applied and you don't want to put it where you will be touching it much. I have had some that lasts for a few hours. Also depends on the Mfg. The link I gave seems to have or had, good stuff. I haven't bought in a while now.

I think if you want longevity, I would try tritium vials. The small ones are almost cheap enough to buy and it's not hard to install, if you can drill a place for them, that allows them to be seen. Other than that, the paint is about the next best thing as far as I know.

This reminds me of those cheap Costco aluminum lights with their XPE emitters (now XPG) that come in packs of 3.

They come with translucent tailcaps and have red LED low battery indicators in the tailcap.

I guess 2ma of loss. I don't think it would mess with mode switching or anything, but I'm just an amateur. I'd wait for a real electronic savvy member weigh it.

Makes sense, but I wouldn’t know which resistor to use.
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That’s the problem, other than a few heavyweights, I don’t know who to listen to on these questions…

^ There are calculators online where you put in the various parameters.

I just realized you would need a limiting resistor in series with the LED like in your diagram. If not, when the driver turns, the LED will be allowed to draw all the current it could take.

EDIT: Here is a calculator.

Where would the positive side of the led actually receive positive? The body would be negative whenever the switch is on and dead whenever the switch is off? It’s still DC and still has to have positive and negative for the circuit right? The circuit, with the switch on, is the driver/led circuit, not in the body. With the switch off, there would not be one. At least I would believe so.

Right. I misunderstood your first statement.

So I would just need to add a resistor on the driver bridging Pos and Neg, and another one on the switch PCB maybe?

I may have an improper understanding of this, but…

The current has to flow in a complete circuit, which includes the tailcap. The current doesn’t just flow to the driver, but through it as well. Normally the current would flow through the switch when it is on, but this would be a bypass for the switch so that the circuit is always complete by going throught the limiting resistor and led.

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I figure if I can keep the amp draw down to 2ma, it would take 40days to completely drain a 2000ma battery, and I can always partially unscrew the tail to lockout/disable the “locator” led

^ Correct. The body of the light is much more connected to positive (via the driver circuits) then it is to negative when the tail cap switch is off.

Pilotdog68 wrote:

. . . So I would just need to add a resistor on the driver bridging Pos and Neg, and another one on the switch PCB maybe?

You may not need one on the driver if it has enough parasitic drain. If it didn't, then yes. You have me intrigued. I may try to make a simulation of this (just not stuffed into a tail cap) to see if it works. I too would like to have illuminated tail caps on 2 of my lights. What FW and driver would you use?

The tailcap light would obviously be completely independent of FW, but for what it’s worth I always use some version of STAR on one of wights drivers.

I think I will try to wire a driver, led, switch with an led tonight to see how it acts. I'm wondering if a limiting resistor would be needed in the tail cap. I would think that once the switch is closed, the tail cap led will essentially be bypassed (not the word I want). It will a have negative charge on both sides. So only positive resistance in the driver would be needed. Not sure.

The resistor would be needed for an smd led to drop the voltage I think. Most of the best options need ~1.7-2.0v

Oh, there would be resistance in series with the LED. It would just be in the driver.

To “make nails with heads” as we are saying here in Germany I did a quick test to see if the circuit from OP works. I’ve connected a LED with an 470 Ohm resistor as protection between body and negative BAT (as would the switch do) and I can say: it depends on the driver!
First one I’ve tried was the one I’ve built-in today in the Convoy M1 Host. It is the “SKU 1127403 - 8* AMC7135 4-Group 2~5 Modes LED Flashlight Driver Circuit (Generic) https://www.fasttech.com/product/1127403” that I’ve used. And the LED’s lid up! But not much. For testing I used ultra low current 5mm LED Red 620-625nm and Green 515-530nm and the green one got about 75uA (MicroAmpere!) and another type 50uA; the red about 150uA.
I had these LED because some time ago I researched the innards of an USB-controlled 230V power strip which had LED’s connected via a 1MegaOhm resistor directly to 230V AC. I couldn’t believe at first that this was possible (I’ve added some 1N4148 anti-parallel later as protection). The thing I’ve learned was - there are LED’s today whith visible shine at very low currents. A great help were the pages of Don Klipstein found here: Lo-mA LEDs
Another Light (Ultrafire SK-98 clone) with the typical generic China driver unfortunately did not work. The LED shortly flashed and the current was only about 8uA.
So, you have to test it to see if it works. Of course, one could add a resistor in parallel to the driver to increase the quiescent current. The 470 Ohm resistor is presumably not necessary but was the first at hand. For the intended function it has no influence at all.
So far my tests suggest that it would be best to test the light in question by simply put a LED between BAT and Body with tailcap taken off and see if it lights up. Worst case would be that it burns up :wink:
If successful, you only have to find a suited LED which mets the criteria above and fits the designated place…
One further aspect would be however to find out if the “standby” LED affects mode-switching which is based on short interruptions of the switch.

I love a proof of concept!

Good point about mode-switching, I hadn’t thought about that