Audible knock detectors

[Mike Wesley]

Dave Plummer wrote:
> 
> Allow me to revise... anything less than $140? :-)
> 

Here's something I fooled around with on the dyno when I was a Ford
engineer...worked pretty good, cost about $10.
Go to Radio Shack or wherever and get a CD to Cassette adapter.
Basically one of those things that allows you to play a portable CD
player through your cars existing cassette deck (assuming you have a
cassette deck).
Cut the mic jack end off that would normally go to the CD player and
wire that to your knock sensor. Pop the cassette in, turn the radio up
(not too loud though), you SHOULD hear a constant buzzing sound. Knock
will come as loud pops through your car speakers.
I made a small filter circuit, but it still works good without that.

Mike...
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