Knock sensor specs

[kv at us.ibm.com]

I built the knock sense detector-  it works fine-  just hook it to the wire
going into the ECM though...  this is a full (rail-rail) logic signal.
Hooking it to the output of the knock sensor will not work.  When you look
at the ECM wire you should see a negative pulse when you rap the block.
All the 555 does is stretch it out so it is long enough that you can see it
on an LED or a beeper.

If you are still having probs...  let me know.

________________________________________________
  Kevin Vannorsdel     IBM Arm Electronics Development
   408-256-6492                Tie 276-6492     kv at us.ibm.com



"Bruce Plecan" <nacelp at bright.net> on 01/28/99 05:14:13 PM

Please respond to diy_efi at efi332.eng.ohio-state.edu

To:   diy_efi at efi332.eng.ohio-state.edu
cc:    (bcc: Kevin Vannorsdel/San Jose/IBM)
Subject:  Re: Knock sensor specs






-----Original Message-----
From: Barry Tisdale <btisdale at cybersol.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Thursday, January 28, 1999 7:58 PM
Subject: Knock sensor specs


>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).

The one off the GN has worked for others,,,,,,  What did you use for
trigger?.
>
>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.

There are degrees of knock retard, and knock counts (0-255) the
knock counts are the number of counts heard in 1/8 of a second.
Some calibrations for some reason just run 0-255 knock counts, and
repeat that continually.
Bruce
>
>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
>