FW: Electronic timing advance

Bruce Plecan nacelp at bright.net
Tue Jan 26 22:12:33 GMT 1999


Hmm, ya got me wondering now, cause mine wouldn't trigger very easy.  Took
12v as I recall..
  Also, the KS wouldn't it be very "spikish" in nature, rather than a
square wave, unless the on duration was very short.
Bruce

>My results seem to be a little different then what you have found, but I'm
>not done yet. My first step was to hook the knock sensor output up to the
>scope and rap on it with a metal rod. It looks just like you would expect
>from a microphone, with a max output of ~3v (with a 'good' strike).
>
>So, the ESC module is on the bench, +12v supply, scope on output, and
>a function generator (sine wave), on the input. The ESC module is a HKM
>from a '87 305 Chevy van.
>
>It appears as though the module responds mostly to a rapid change in
signal.
>Either a sudden increase in amplitude, or a sudden change in frequency.
>It appears that the freq range need be in the 2KHz to 17.5 KHz range.
>
>I haven't found a 'sweet' spot that would cause a continuous knock signal
>output. The max p-p volts input that I've been testing with is 2.5v. If I
really
>crank up the volts, I can get a continuous output at almost any input freq.
>
>For the curious amongst us, the circuit is built on a thin ceramic plate
>using silk-screened on resisters, some SMD capacitors, and a single
>SMD chip (18 pin). The board was 'encapsulated' with a clear jelly like
>substance that cleaned off with a toothbrush. The resisters are laser
>trimmed for value.
>
>BobR.
>
>Who at this point is thinking that verifying the above on another module
>would be a good idea. No sense in doing all this with a module that might
>be/is bad.
>
>Who is also thinking that a tape recording on a running auto, of the
>knock sensor 'sounds' like something to try.
>
>
>Bruce Plecan wrote:
>
>>At one time I had a dozen or so esc on the bench, what exactly do you need
>>to know?.
>>In crash testing them, using a 555 to generate the KS they all seemed to
>>listen
>>to 2 frequencies.
>>If you want I think I got the diagrams for the 555s to generate the KS
>>signals.
>>The 555 generators kinda overwhelm the ESC so the results aren't terribly
>>accurate, if your tuning them.
>>Bruce
>
>BobR wrote:
>
>>>Who now has a 305 truck ESC module on the bench, trying to find
>>>out the how/what/why/where of this unit.
>
>
>--
>
>




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