knock signal

ty1548

ty1548

Member
Anyone know if the knock signal goes high or low when knock is detected? According to the GM doc., the signal goes low. However, there is a schematic for a DIY knock detector shown on the chitownsyty site that, according to my analysis, would only work if the opposite were true, that being a high signal when knock is present. TIA.
 
sytyguy

sytyguy

Moderated User
I don't think that's the answer he was looking for......

Todd.....Don Broadus did some testing years ago and shared it on the diy-efi/gmecm board on this same subject. Here's his post:

I have been experimenting with ESC modules and knock sensors and have found that both detect a wide range of frequencies. By using the output of a HP3324A function generator connected to DR 562 knock sensor coupled with a 1/4 pipe to another DR 562 knock sensor I was able to track the freq. curve of the sensor. The sensor responds to sine, square, and triangle waveforms with no loss of signal output. With 1 V-PP sine wave in and monitoring the output with a scope the DR 562 sweet spot was 6KHZ. A loud tone could be heard at 6KHZ indicating resonance. 7-10KHZ had good outputs. The voltage dropped off at 12 KHZ . An output was observed up to 50KHZ very small amplitude 4 MV-PP. The ESC modules that I have tested so far are HKD, HKM, HKR, BLN, AFWB, and ANRZ. With the DR562 det sensor all ESC modules responded at 6,9,10 KHZ. The ESC output is approx. 10 VDC with no knock and goes to 0 VDC for Millsec then back to 10 VDC with knock. All ESC testing was at 10 VPP sine wave input into the first DR 562. the second DR 562 outputs to the ESC module. The ESC output toggles low/high with each knock like a one shot multivibrator and never has a continuous low output. When I find some more knock sensors I'll run a profile on them.

Also, there's some useful info in this pdf (third page):

http://www.smpcorp.com/download/view/TT1Q02.PDF

Not sure if this helps ya any. I wish I could help more, but that's all I've found thus far......

Michael
 
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