homemade knock sensor setup?

[sleepr]

If I remember right a knock sensor puts out ac volts that it makes under knock, if you were to put a knock sensor on a car with out a factory knock sensor and wire it into a re-lay so when there is knocking it trips the re-lay and allows 12v’s to light up a red l.e.d. I think it’s a sound idea but would ac voltage trip a re-lay?

a knock sensor like this
http://cgi.ebay.com/ebaymotors/ws/eB...category=33625

[Pineapple]

The ECU suppose to count how many knocks in a sec to decide if it need to do anything.
You need more info on the sensor like how much Voltage it output or its a current signal, or a pulse signal.

[CraigW]

The piezo element cannot generate enough voltage/current to drive a relay. It would require processing.

[white90dx]

Get a J&S Safeguard unit... Problem solved. You aren't going to be able to do it by yourself without significant electrical knowledge.

-Charlie

[sleepr]

i hear yea