I am trying to activate a relay when the vehicle is in anything other
than Park. The transmission module sends out 5V @ 120hz with varying
pulse widths. In Park, I read 0.71V with the meter and looks to be
apprx 1/7th of the pulse on the scope (square wave). In Reverse, the
pulse is measured at 1.6V of 1/3 of the pulse with higher voltages and
pulse widths in N,D,2. I've tried using this to enable a small dc
relay, but only get chatter (even in Park). I've been told I could do
the following...


RC Integrator - Unity-Gain OpAmp Buffer - Comparator


How would this work? Any help is greatly appreciated.