Is it generally a 0-5v signal, or is it a different kind of signal that needs some circuitry to make sense of?
I have a tacoma with a 2.4 liter engine, and would like to hook the knock sensor up to my zeitronix datalogger into its 0-5v input, but I am not sure that it will be as simple as that.
Knock Sensors: What do they output?
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Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
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Jim Blackwood
- MegaSquirt Newbie
- Posts: 28
- Joined: Thu Jul 29, 2004 5:31 pm
- Location: Gunpowder Rd
It is not. You'll need some sort of signal processing circuitry because the knock sensor is apparently some sort of a mechanically resonant circuit. I don't know if this is done with a piezo crystal, (haven't taken one apart) but I suspect that it is, which would mean that you get an AC output at the resonant frequency, of unknown amplitude but which should vary depending on the strength of the knock signal and placement of the sensor. The circuitry you need will take this signal and convert it to a digital signal based on a threshold value. One option is: http://www.megamanual.com/ms2/knock.htm
Phil Ringwood has another circuit which is tunable, I believe for the threshold value: http://megasquirt.sourceforge.net/extra/knock.html I have this circuit installed in the proto area of my new v3.0 board but haven't had the chance to dial it in yet. However, a lens in the case over the LED and a hole in the side fitted with a custom made screwdriver for an adjustment knob means tuning should be easily done and I may be able to do that tomorrow. However, you then have to input the signal to the MS properly and set the parameters in MS for the knock detector. Others have done more with it than I have though.
Phil Ringwood has another circuit which is tunable, I believe for the threshold value: http://megasquirt.sourceforge.net/extra/knock.html I have this circuit installed in the proto area of my new v3.0 board but haven't had the chance to dial it in yet. However, a lens in the case over the LED and a hole in the side fitted with a custom made screwdriver for an adjustment knob means tuning should be easily done and I may be able to do that tomorrow. However, you then have to input the signal to the MS properly and set the parameters in MS for the knock detector. Others have done more with it than I have though.
Jim