PD that looks awesome! I know we discussed it briefly in another thread and maybe I just missed the follow-up details here, but how did you accomplish that? Or is that done by brute power/leaving out parts?
Be, er, thoughtful about the 405nm emitters.
That’s close to the edge of perception, for most people’s vision — the retina has to intercept a lot of those high-energy photons before you see a faintly visible color.
Both rev 5.1 boards and the rev 6 board. Can’t wait to test that one. So, the bleeder resistor is going to have to change, the old 560 can’t supply enough to run it all???
Mm in my experience the 560 bleeder does fine all the way up close to 0.75ma draw in the tail before the driver starts acting weird. I expect it to still be fine with Rev6, but I guess we’ll find out in a couple weeks
I apologize if this has been suggested already. Has anybody considered putting one of these dual LEDs in the tail?
The green has a Vf of 3.3 and the red has a Vf of 1.95. Wouldn’t this work as a “dumb” battery level indicator?
I found a few green LEDs with a higher Vf but they were more expensive. My thought was that multiple greens that fall off at various voltages would allow the light to shift away from green, to yellow (green+red), to red.
EDIT: If we could find an appropriate LED where the lowest Vf is around 2.8 wouldn’t that be ideal? That way when the LED goes out the battery is depleted and won’t discharge any further.
It’d be great, but frankly, it doesn’t seem to work that way in my testing. I’ve used these led’s which have a rated Vf of 3.0-3.2v, and even with a limiting resistor in series, they are still giving off a little light at ~2.5v input. Eventually that would stop, but the listed Vf’s are usually at normal operating currents, not a strict cut off voltage.
OK, so the consensus seems to be that using the LED Vf to prevent over-discharge probably won’t work. What are your thoughts on the dual LED that should shift its combined color spectrum as the voltage falls?
IIRC, the dual-LED color-shift thing worked sometimes… but it was awfully sensitive to the wrong things — didn’t work the same on multiple units (or even one unit with different cells), and still didn’t really cut out at the desired voltages. But you can do it if you’re willing to fiddle with it a lot.
That’s much of why I’m hoping the smart version of the tail board will pan out. It can be more more responsive, consistent, and explicit about the cell status. And, if desired, even animated.
I can’t wait to see first results of the smart tailcap.
TK, I had a look at your firmware, but due to my lack of knowledge I have trouble understanding what it does… But I think I understand enough to say it’s cool. May I ask some questions?
That colorful swirl… it does it on every boot. So would it start blinking on every short press?
When is the MCU sent to sleep? If watchdog wakes it up every x seconds, basically all the functions like ADC (and that other stuff on page 32 in the t13A datasheet) could be turned off and the port pins can be set to inputs before going to sleep for power reduction, right?
I think we would need a firmware for calibration, right? Could we just use battcheck for that, or would we need something different here?
Yes it works sometimes, and as ToyKeeper pointed out, is very sensitive to about everything, especially the battery type. So for each combination of battery and driver you will have to figure the values out. Thusfar it never worked for 18650 batteries: I tried the same blue/red tail-board that worked well enough on a 16340 flashlight (blue fades away between 3.7V and 3.8V with red still bright) on a BLF-A6 and the blue led stayed lit brightly until the low voltage protection (2.8V?) kicked in.
Also a zener diode did not shift the voltage at which the leds started dimming: at these very low currents things appear to work different.
My current EDC (Supfire S1 host, 3-mode FET-modded AK-47 driver, sliced Nichia 219C):
16340 IMR battery, red 603 tail-led with some resistor (forgot) + dedomed XM-L2 (6A1 80CRI ) tail-led without resistor, 680 Ohm bleeder resistor on the driver. With a full battery the white led is clearly brighter than the red led, once the two leds appear the same brightness to me, the battery is half empty, between 3,6V and 3.7V, the white led fades further when the voltage is getting lower than that.