VR trigger fan noise
This page is about a strong (600W) PWM fan in a car, located in close proximity of the crank VR trigger:
I've found the strange situation of VEMS starting fuel pumps and injectors with stopped and stand-still engine when the fan operates. Apparently the fans magnetic field is strong enough to trigger the crank VR signal-
Scope shot of this noise measured on VR signal cable:
It's in the range of +-0.5V, more than enough for LM1815 triggering
This is a normal scope trace of cranking the engine -without fan operating:
I'm looking for solution of this problem.
Since the signal/noise ratio is around 10/1, I've the idea to attenuate the VR signal with a series voltage divider at around 1:10 ratio.