Microlighters

I am going to test this on BMW R1200 fitted to my Zodiac CH650.
Very simple, anyone can built it for +- R20.00. Tapping with the metal part of screwdriver on the sensor will lit the LED.
knock freq. = 900/ (3.14 X piston diameter(in meters)) Works out to +-2.8Khz for the R1200.

Looks interesting. Please keep us posted on your progress.
I would like to use this as well if it works.

Is that sensor part of the R1200 motor or are you fitting your own piezo mic to the motor?
What is the frequency you quote? (2.8kHz) Is that the frequency of the pre-ignition "knocking" sound you are trying to detect?

Sorry for the late reply. Yes, the R1200 has two knock sensors. And yes, with the info I gathered so far that is the audio freq. when knocking occurs.