knock sensor circuit

"Knock" is pre-ignition, and serious knock involves detonation of the fuel air-mixture, producing faster-rising pressures in the cylinder than you get when the motor is running as designed

A piezo-electric microphone on the cylinder block is the usual knock detector. You'd want to compare the microphone output with the spark plug timing to distinguish between the pressure wave coming from the desired, spark-plug initiated combustion in the cylinder and the slightly earlier and appreciably louder undesired "knock", though a high pass filter could probably do a pretty good job of discriminating between the ping of knock and the regular bang of the intended ignition.

I'd be thinkig in terms of a digital signal pocessing chip - perhaps something out of the Analog Devices Blackfin range - but this isn't an area that I know much about. Knock detector circuits were around before digital signal processors got cheap.

-- Bill Sloman, Nijmegen

whatever...

that's not your only problem...

who gives a damn...

It is a short burst of AC signal with frequency components roughly between

4 to 8 kHz. The dominate frequency is determined by the bore diameter. The event itself is very brief so instead of a gage my device flashes a bright LED the duration of which is roughly proportional to knock intensity. See my website for details.

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

void _-void-_ in the obvious place

Here's a link to a TI app note that might help:

Engine Knock Detection Using Spectral Analysis Techniques With a TMS320 DSP

--
Joe Chisolm
Marble Falls, TX

hi, email me : snipped-for-privacy@adam.com.au i have exactly what u need !

mark k

boris, i tried replying to ya email but it dont work. mark k