I had some time to put together the Rev B of the GFS16 LED Taillight board.
Here's how it looks like. The OSHpark boards turned out great, especially with the 45deg. rotation to avoid a chance of the oval-cutout breaking.
The board seems to work just as expected, and has an actual measured current draw of (5.6+-0.1)uA at a 3V LED Turn-off threshold, exactly as expected. This is over 10x LESS current draw than my Rev A version, so I think that's not a bad thing :). As the battery voltage drops, current draw should drop further.
Made a quick video of the board in action, and here's it with a 330 ohm series resistor and a power supply. The threshold voltages are about 3.4V and 3.0V for Low and Off respectively. Note that the bigger the bypass resistor, there will be a larger possible error of the threshold voltages from the voltage divider, as well as a larger hysteresis. This was discussed in some detail in previous posts.
I've also tested this with a 560R bleeder resistor across a Convoy S2+ standard driver, with R3 = 681kR. This gives a 3.55V low-voltage threshold (hysteresis at 3.75V).
Regardless, I just wanted this board to be simple and no frills. Tested all the way down to 0V and it fixes an issue with the previous Rev A design (where if the voltage drops below ~2.5V+, we were out of spec for the comparator, so the red LED could come on again dimly). No such issues for Rev B.
OSH Park boards and parts list are available in the previous post as well as the first post.
Many thanks to all the support I've received on this forums, members who've had good success building their own despite the annoyingly small components, and feedback and suggestions for improvements! Again I understand it's not the perfect tail-light, but it does provide some simple extra features over a regular tailight board.
[Edit] - I understand the components are a little bit of a pain to solder by hand... when I have time I think I'll have a go at changing the components to be larger and easier to solder.
Enjoy!