Knock sensor specs
Clarence Wood
clarencewood at centuryinter.net
Fri Jan 29 16:46:56 GMT 1999
I missed some of this thread....where can I find the schematic for the knock sensor detector??
Clarence
At 06:22 PM 1/28/99 -0700, you wrote:
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>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
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>"Bruce Plecan" <nacelp at bright.net> on 01/28/99 05:14:13 PM
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>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
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>-----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
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>>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).
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>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
>>
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