I had this sound happen with my PL47 but on no other FET light in any mode. Wasn’t just in strobe either, you could hear ringing that changed pitch as it was ramped up and down in normal mode.
Oof, probably not the most ideal circuit design. 
Thanks for measuring the aux led power usage again.
Yes. I’ve noticed this on almost every FET-based light I have.
On some early designs, the ringing would actually make the attiny chip reboot. This happened both on strobe modes and on regular PWM’d FET modes. Each time the FET closed and stopped current flowing, it made a voltage spike well out of the attiny’s specs and tolerance. But the circuit designs were updated to soften and absorb that spike, and I think all the current designs have at least some similar measures included.
I think the dampener is between MCU and FET though. I’m not sure if it helps protect the FET itself, or just the MCU. Probably some of each, since IIRC it softens the edges of each pulse. But I don’t have a scope to actually measure it.
The Emisar products are probably fine, since the drivers were designed by the same person who identified and fixed the ringing-reboot problem in the first place. I’m not sure about other brands though.
its funny, my d4v2 cant start fires, tried it today was curious and used it with a piece of paper, ended up blinding me temporarily. feels like i was looking at the sun for few minutes.
I’m just guessing here but it’s probly because it’s running anduril ,which means it can’t be on full power more than a few seconds because of the aggressive step downs , you can start a fire with a D4 with ramping ui or ramping v2.
To ignite paper using light, it helps if the paper is black or dark-colored.
Also, I finally updated the UI diagram. It shows the new features now, mostly. It’s getting quite crowded though, with all the different functions available.
Draw a dark circle on the white paper, I think that would help you to ignite a flame.
Does anybody know the o-ring size for the D4v2? Thanks
Don’t know if it was covered earlier in the thread, but is it possible to alter the Anduril source to change the colors of the battery status aux leds? Like change it from the stock blue/green/red to green/yellow/red or green/blue/red, for instance?
could someone please explain how the battery status aux LEDs work? Thanks.
It is a mode you select. The mode will show blue, green or red depending on the battery voltage. The updated UI graphic shows how to select it. When you are cycling through the different aux color/modes there is the slow cycling rainbow and the fast cycling rainbow. The fast cycling rainbow is the battery voltage indication mode. When you finish selecting the mode it will then show one of the three colors.
While I am sure it is possible to do, TK hasn’t released all of the source code files for this model yet (someone correct me if I am wrong).
Just received my D4v2 in SST-20 3000K and wow, it’s a very nice light.
Unfortunately I have found a problem with it:
When I click or click+hold the button from off the flashlight sometimes (maybe 1 in 40 clicks) does not turn on - nothing happens.
The click from the button sounds and feels normal when this happens so I don’t think it is a problem with the switch itself, because it ONLY
happens when I try to turn on the flashlight but never when changing modes or turning it off.
It took me one or two days to notice this problem because it doesn’t happen very often and I wasn’t sure if I made a mistake when playing
with the light and learning the Anduril UI.
But when I picked up the light from my desk and tried to click it on and nothing happened it became clear that something was wrong.
I am using a Sony VTC6 18650. I also cleaned all electrical contacts, this didn’t help.
@ToyKeeper
Do you think this could be software issue? I just found this bug report Bug #1803918 “fsm: sleep ticks interfere with button presses?” : Bugs : Flashlight Firmware Repository which seems to describe a similar problem. I am using the Aux LEDs as battery indicator, though.
Read this post regarding the issue.
https://budgetlightforum.com/t/-/47204/814
The microcontroller wakes up approximately every 30 seconds to measure voltage, and it will not respond to input for a very short period of time.
Please add info about the lens:
~25.64mm x 1.5mm AR coated
Is this bug only there because of the aux leds and them needing LVP? And does this also occur if you turn the aux leds off?
I switched to a static Aux LED colour (green) and it still happens.
It is for LVP so the aux LEDs do not drain the battery below a safe level. It will happen no matter what mode there are in, probably when they are off also. However I have not reviewed the code so I am not sure how TK programmed the feature.
Thanks for the reply Mark.
Well, I really hope this can be fixed. A flashlight that doesn't turn on 100% of the time when clicked is not reliable IMHO. :-/
Changes to the code can definitely fix the issue. If it bothers you it is possible to disable the feature in code and reflash the firmware. Once TK releases the code anyway. I have had it happen once or twice but to me it isn’t bothersome, but I can understand where you are coming from.