I was thinking the other day about that board with the Tiny13 pads.
It was most likely already mentioned before I started reading this thread but it would be cool if it could read voltage and change the tailcap color as voltage dropped and also act as a LVP and shut down the LED’s entirely once voltage got low enough.
Obviously keeping the drain low enough is an issue but should not be that hard if TomE is doing so well with narsil.
ah, if only there were more hours in the day….
On a different topic now…
Some of you have already seen my X2R mod. I thought I’d detail a little more about the tailcap in that one.
I used the newest Rev5.3 boards that use the jumper pins. It was a bit of a pain to get them aligned correctly and make sure they were solid without poking out the other side of the board. The end result is very clean though so I will keep using this version.
I was able to get by with a 1k bleeder on this one and still keep driver function. I’m not sure if maybe the charger circuit has a bit of bleed itself that is helping me or what, but it’s nice to keep the bleeder a higher value. I used two 50k pots for the whole board (that I can switch between settings), and added about 10k of resistance on just the green channel to make it more balanced. The blue still fades out first as battery voltage goes down, and overall it is still too bright, so I ordered some 100k pots to try. It’s a shame the camera can’t pick up how it actually looks, it’s really beautiful.
I think what was said is that the Attiny itself draws 5x as much power as just running the LEDs. TK was working on some stuff that would actively give low voltage feedback, but nobody really tested it.
Is here any version of 2-board design where upper (with leds) board is one-side?
Do either of these two fit what you are looking for?
The original Rev5 top
or
Rev5.1x, explained here.
Note: 5.1x hasn’t been tested that I know of. The only thing I’m worried about is the switch boot smooshing the LEDs if they aren’t inward enough.
I cannot understand how does it works, how does leds negative pads are connected to the “-”? Bridge from other side?
5.1
On the 5.1x, it jumps a trace on the back of the board, yes
My Thorfire TG06 AA/14500
dual white led with 2k pot (from memory) the tail light pulse blink every 0.5 second like a heart beat 
. No bleeder needed 
Hmmm I kind of like the white look in there. I might have to try that.
I have actually been considering some white LED’s but didn’t order any and I have not even built one yet. With 90+ degrees in the house lately due to the AC being busted I just haven’t seemed to get as much done as sometimes lol.
Is that tailcap blue? What gives it the blue tint?
Also what causes the pulse? That is actually not a bad idea in some cases.
I would love a slow pulsing. I’ve seen it built into some 5mm LEDs. but never in a small SMD size.
The second pic show slight blue tint because my iPhone camera is sux at white balance colour.
I used clear tail boot and the light white.
I like this idea 
I do too but to get the drain low enough to not be worse then leaving the LED’s on by themselves would take someone that knows how to program ATtiny’s way better then me. I could most likely cobble something together that would do it (pretty simple to check voltage and activate a pin based on the voltage) the issue is reducing the parasitic drain enough to not be worse then the LED’s
If possible it would be best if the tiny could sleep entirely except for the single pin activation for ~30 minutes between voltage checks. It would not need to do anything at all during this time. If it lost power (aka, you turn on the light) it would reset the cycle and update the voltage check.
During a discussion I had recently the possibility of a lighted tailcap compatible with NiMH batteries came up. I have very little experience with this sort of thing, but I did a bit of poking around. It would seem a very simple circuit using something like this might work. That converter, a suitable inductor, and a couple of other basic components would be all we need. I think there would be enough room on the bottom side of the 5.1 boards.
Would that converter work for this application or am I missing something?
It has been discussed before I think. Basically, you’d need an entire boost circuit tail-cap ‘driver’, just like you would in the head for the main LED. I don’t think it would be very efficient to drive it (considering the flashlight is supposed to be ‘off’), and the two drivers might interfere with each other.
Is there actually a need for a full driver w/ MCU etc.? The converter I linked doesn’t appear to need a separate controller.
The schematic on page one shows that converter, an inductor, 2 caps, and 2 resistors. That’s all that is required.
When you convert to watt/hours a standard eneloop actually has more capacity than an efest 14500. I just did a lighted tailcap that was pulling .25mA, and it was excessively bright. At that current I expect that cell to be good for weeks. It seems a runtime of weeks on a NiMH could be obtained at a reasonable brightness.
I’ve yet to put one of these together, but wanted to for my next triple build using a 32mm Noctigon. What about utilizing the center led mount for one of these tailcap leds which would shine up through the optics when the light isn’t turned on? I think mounting it and running wires from a bleeder would be easy, but not sure how to disable it once the light is turned on since it wouldn’t be directly linked to the tailcap.
Using central led on xp32 is my old dream. There are lots of color leds in XP size.
It will be great if smb could combine teo ideas from this thread (blinking led+powering one of leds mounted on main pcb). I think there will be no need in turning this extra led off, it wont be visible when main leds are running.