Active wheel speed sensors

[NArcher]

Has anyone tried tapping into the Active wheel speed sensors on newer cars? They produce a pulsed, 50/50, .6v DC square wave signal that varies in frequency. I tried using the nitrous input pin to retrieve the signal, but to no avail. If anyone knows another way, please let me know. Thanks

[NArcher]

Since the signal is so small (.6v in amplitude), I probably need some type of amplifying circuit of up to 5v for MS to "see" the signals. I am correct to assume this?

[Matt Cramer]

Are you sure it's not a VR sensor? Even if it is some weird 0.6 volt Hall effect, I suspect a VR conditioner circuit would work.

[racingmini_mtl]

If there's no zero crossing, that will require a circuit that can handle it. The LM1815 and the MAX9926 won't work with a 0.6V DC signal.

Jean

[NArcher]

I tried using a VR conditioning circuit, but with no luck. It's very different from a VR circuit. From my understanding, VR sensors don't require a 12v input to power the sensor. These active wheel sensors are what's known as either a "magnetoresistive" or reluctance sensor. Neither sensor has a ground input. Instead they use a "floating ground" (not sure what that means) and "Active WSSs output a digital signal. The signal is a Direct Current (DC) square wave signal. The signals are different than a camshaft or crankshaft position sensor. " (Taken from this website: http://www.underhoodservice.com/Article ... copes.aspx ). 3/4 way down the page has more info, "What is unusual is the voltage levels of the square wave pattern. The wave goes from between .6 to 1.2 volts. The square wave is only .6 volts high and never connects to ground or zero. Also, it never shows the battery voltage. This is a very small square wave out of an active sensor. " That's pretty much all the info I have to go on for now. Let me know what you guys think. Thanks

[fixmann]

Hi

Are you going to use only the sensor or is the original abs system going to still be present?
I think this can be solved

Fixmann

[NArcher]

Sorry for the long reply. The orignal abs system will still be in place to handle abs functions

[billr]

I'm a bit out of my element here, but won't capacitively-coupling that .6-1.2 wave make it "zero-crossing"? It won't be much of a square anymore, more like pulses, but I would think it would trigger a VR input conditioner fine.

[racingmini_mtl]

I'm a bit out of my element here, but won't capacitively-coupling that .6-1.2 wave make it "zero-crossing"? It won't be much of a square anymore, more like pulses, but I would think it would trigger a VR input conditioner fine.

Yes it would make it a zero-crossing signal. That's actually what is done on the JimStim to emulate a VR sensor signal. Normally you wouldn't do that on the car because it affects the timing of the signal but since this is for a wheel speed sensor and not an engine position sensor, it should not be a problem.

However, that quite a small voltage so some tests would likely be needed a good capacitor value to work with the VR conditioner circuit used. It might need a MAX9926 to work since it is quite sensitive.

And as opposed to what I said in my previous message, it would be possible to use the signal directly (no capacitive coupling) with the MAX9926 but it would have to be set to operate in mode A1 with a bias voltage below 0.6V. That would require making a board for this circuit and soldering the surface mount chip.

Jean