Knock sensor specs

[rauscher at icst.com]

15mV AC from the KS seems low, what did you use to measure the output? If a DVM,
remember
that it averages over a period of time.

To trigger your 555, you need to get the signal from the KS filter module. The
GN systems have this
as a seperate unit that plugs into the ECM harness. Easy to get to.  If your
system has this, tap
into the filter output, which goes low during knock detection. Trigger the 555
though a .01uf cap, with
a 10K Ohm pullup on the 555 trigger pin.

If your working on a '730 ECM, or another that the filter module is internal,
I'm not sure what to
tell you. You could either wire in an external filter or tap into the ECM for
the knock signal.

BobR.

Who needs to dust the wood chips and plaster off his cone shaped hat,
and get back to the bench to finish the KS filter work...



Barry wrote:
>Since the KS thread began, been thinking how important it is.  Did some poking
around, after putting >together the 555/LED monitor (which didn't work).
>
>DC on the KS is 2.36v; solid rapping on the block near the sensor puts an AC
voltage of maybe 0.015v >tops on the sensor line.  Scan tool reads knocks, but
the value presented can be anything from 1 to >255; when it hears a knock, new
(seemingly random) value is set & held till the next 'knock' comes >along. 
Knock retard degrees always reads zero.
>
>Don't think 0.01VAC is enough fluctuation to trigger the 555 reliably; even
using a comparitor, that's >barely enough signal to pick out of the background
noise - lots of ignition wires nearby. 
>
>Are these readings within normal limits??  Helm manual just says "an AC voltage
should be present" >(when rapping) - no value given, but 0.01v seems real low.
>
>Thanks for any feedback - Barry