So it is a reluctance sensor

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Hi there I made a simmilar question some days before.

I am trying to count the gears while a tractor is moving. The counter will be an AVR which will make some calculations in order to give some details vs the machine operation time and the speed. The details will be in a graphic display as real time graphs.

There is a ground speed-geartooth-reluctance sensor with only 2 cables positioned very near the gear teeth. The vehicle's battery is a 12V. The sensor has a label in each cable (A and B). I have measured the output of the sensor using the circuit:
1. 12V DC then in series
2. Resistor 10K then in series
3. sensor's cable labeled A
4. sensor's cable labeled B to GND
Measuring the drop voltage across the resistor with an oscilloscope I see an anodic sine curve when a tooth comes, then a cross over depended on the tooth length and then a cathodic sine curve when the tooth left.

I made all these not on the tractor but on my desk. The sense of this sensor goes in a monitor that shows the ground speed of the vehicle. So does anybody knows what is the internal circuit inside the vehicle supports and read the sensor? Is there any standard? Is there any circuit I could use to read the sensor without effecting the vehicle's inside circuit. I tried the google but not a lot of things (just theory).

Thanks a lot.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

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LM1815 does all the signal conditioning for you, but I'm not sure it can be paralleled to the existing circuit.

Otherwise use a simple differential amplifier with enough gain, but you probably need dual power supplies as you can't bias the sensor to halfway the supply.

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Anything else without using the LM1815???
I forgot to say it in my last message

thanks.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

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icarus1 wrote:
Hi there I made a simmilar question some days before.

I am trying to count the gears while a tractor is moving. The counter will be an AVR which will make some calculations in order to give some details vs the machine operation time and the speed. The details will be in a graphic display as real time graphs.

There is a ground speed-geartooth-reluctance sensor with only 2 cables positioned very near the gear teeth. The vehicle's battery is a 12V. The sensor has a label in each cable (A and B). I have measured the output of the sensor using the circuit:
1. 12V DC then in series
2. Resistor 10K then in series
3. sensor's cable labeled A
4. sensor's cable labeled B to GND
Measuring the drop voltage across the resistor with an oscilloscope I see an anodic sine curve when a tooth comes, then a cross over depended on the tooth length and then a cathodic sine curve when the tooth left.

I made all these not on the tractor but on my desk. The sense of this sensor goes in a monitor that shows the ground speed of the vehicle. So does anybody knows what is the internal circuit inside the vehicle supports and read the sensor? Is there any standard? Is there any circuit I could use to read the sensor without effecting the vehicle's inside circuit. I tried the google but not a lot of things (just theory).

Thanks a lot.

I guess, you hav a sensor based on a loaded oscilator.
Feed it vidth 9V and 2K in serie. Then unloaded, unloaded, the sensor draw 1 mA, Ri = 7K, V acros sensor = 7V.

If you load rhe sensor, it draw more curent, 3 mA, Ri = 1K and the V acros are 3V.

I use a LM358-like OPAMP, gain = 3, clamp the output by a 5,1V zener, but a CD4049D / CD4050 should also do, - VCC = 9V.

HM

HM

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Hi there,

I have finished the project about 1 week ago. What a coincidence I have used the same op-amp. I found some data that telling me the sensor's functionality and I did it.

Anyway thank you very much.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer