Thread: Seeing PWM Data
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Old 01-11-2019, 04:25 PM
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wpoll wpoll is offline
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Originally Posted by andrewwynn View Post
You're curious what waveform the LCM sends to the corner lights I could probably fire up my scope meter and see what it sends.

I noticed that the two filament bulbs only use the high output filament but at lower voltage. In the back half the red lights use PWM half use both filaments very strange. I have 01. I think after 03 they all use only PWM.

I put lights in for turn signal I had to go back to Incan in front because the led won't come on for running light.

In the back it works but I get fast flash because low power. I did notice when I use hazard flash that bulbs actually blink really fast eg PWM activity going on. I believe LCM uses pwm to clamp output to 12v. Not sure why I don't see the pwm blinks during normal turn signal. Maybe that's allowed to run full voltage.
I would do the same (fire up my 'scope and check the PWM freq. and duty-cycle etc.) but my signal lights are only that - signal lights, so I can't help much.

I do know that the signal lamps are under full PWM control - they glow brightly as signals but glow dimly when a halo fails and they get switched on in a "replacement" role until the halo lamp is replaced. This is on the LCI car - not sure what pre-LCI does.

Interesting comment, Andrew, about the signal having two filaments. The LCI cars have only one (or at least my Euro-spec one does). Same for the tails too, as has beed discussed before - I just didn't realise the front signals were dual filament too (on pre-LCI). I must look more closely at the wiring diagrams for the pre-LCI cars sometime...
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)

Last edited by wpoll; 01-11-2019 at 05:09 PM.
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