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While sorting through some photos I noticed my 4-dot DRLs just kinda.. shut off for an eighth of a second? They don't appear to be PWM or have any flicker at all to them, which makes sense as they are DC powered. Verified with a 480fps camera, which is a 2ms resolution. The camera shutter in these photos was 1/125, which is an 8ms resolution.
Yet...
The only thing happening here is I'm turning to countersteer, and probably giving it the beans. These three photos are all within about a half second.
PSM was on sport in these photos, so the only thing I can think of here is at the moment I hit center on steering it likely started to intervene, and the power draw cut out the DRLs momentarily? No errors, no warnings, nothing indicating this that I've noticed in the cabin. If it wasn't for these photos I would have never known.
its how LED react with camera lenses. you can see for yourself too by having the car turned on and then stand in front with your phone camera. you'll see the lights flicker.
I've seen numerous videos that show the same flickering of LED lights both front and back. Don't know the science behind this but it can be considered as normal.
Specifically, most car headlamps that are LED are DC current as opposed to AC current, so what they actually have is a DC to DC converter from the "internal" car's voltage system - 12V through to 48V typically - up to 70V - 100V for the LED headlight, and goes from a variable-ish battery voltage to a constant, smoothed voltage (or current) for the LED. The voltage regulation here is called Pulsed Width Modulation where the electronics go from full on to full off rapidly - at a frequency that is not visible to the human eye. Typically, for dimmable circuits, it's around 120Hz AFAIK. In any event, this cycling on and off is what you are seeing, an is an artifact of two things (a) the fact that the lights use a PWM DC-DC converter, and (b) your camera shutter speed (particularly the rolling shutter for video), can capture these brief moments.
Okay, so what's being missed here is the whole 2ms resolution test coming up negative for flicker.
Photos? 8ms resolution.
Video? 2ms resolution.
No flicker in the video means there can't be flicker in a photo. If the lights are in an 'off' phase for under 2ms (as shown by video seeing no flicker), then an 8ms photo could not possibly show the lights as off, but as you can see in the OP... they do.
Update - something is indeed wrong with my DRLs. I'm thinking loose wiring somewhere, but haven't ruled out power delivery issues as PSM was still on when it happened.
Went hooning on the ice today again, got it quite a bit more sideways and was toggling through PSM, PSM sport, and PSM off to see how things behaved. After 5 or 6 laps on the big course the MFD started yelling at me about checking the front left and right DRLs while mid-slide, and the errors went away by the time I got to the paddocks.
Okay, so what's being missed here is the whole 2ms resolution test coming up negative for flicker.
Yeah, clearly I suffered from a lack of reading comprehension - I missed your comment w.r.t. 480fps camera. That said, it's still effectively a strobe effect probably due to some bad connection or voltage regulation or something, but going from "normal" to an "abnormal" condition
Yeah, clearly I suffered from a lack of reading comprehension - I missed your comment w.r.t. 480fps camera. That said, it's still effectively a strobe effect probably due to some bad connection or voltage regulation or something, but going from "normal" to an "abnormal" condition
Yeah, the going theory at this point is that when PSM is actuating ABS it drops the voltage to the DRL drivers enough (either directly or through whatever DC-DC regulator or PWM system) that they power off momentarily.
I'm still unconvinced that the 4 dots are PWM. I think they're either 'on' or 'off'. The behaviour would line up perfectly if they are direct-driven 12 volt LEDs -- the supply would just have to dip below the operating range and presto, you get this problem.
Maybe I'll dig up some wiring diagrams tonight and see how that's all done.
I just got approached by someone after running a little local track.. apparently at the end of the straight, after I let off on the brakes and turn in, the lights flicker. Every time. Visible to the naked eye.
I'm going to see if I can find a safe way to reliably reproduce this so I can get my service manager in on it, see what's up!
02-24-2021, 12:40 PM
DRL Dots Flicker?
