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Thread: Detecting Axles using a Teensy 4.1

  1. #1
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    Detecting Axles using a Teensy 4.1

    I would appreciate advice on creating an axle sensor using a Teensy 4.1 connected to a sensor.

    Basically, I need to detect when a wheel of a vehicle rolls over a thin/narrow aluminum strip which is glued to the roadway and placed perpendicular to the direction of traffic. The system needs to detect when a wheel rolls over the strip. Wheels may roll over the strip every 100 ms.

    I thought of a simple Piezo sensor but the ones I found would be easily destroyed by the wheels. I also tried the Adafruit 9-DOF Orientation IMU sensor but I could not get it to work.

    What is the right sensor to use and a good circuit to connect to the Teensy?

    Thanks in advance.

  2. #2
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    You could try something like the sensor strips that cities put on roads to measure the volume of traffic. I presume what they do is the weight of the wheel momentarily closes a circuit consisting of two wires in what amounts to a rubber hose. If that can be done it's a simple matter of hooking it up to a digital pin and "the rest is just software" (tm)

    Pete

  3. #3
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    Thank you. Yes, those are called axle sensors. They are expensive and require embedding in the asphalt.

    I need something simpler .

  4. #4
    Senior Member BriComp's Avatar
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    The systems used in the UK for temporary speed measurement consist of a rubber tube with one end (the far end) closed and I assume a pressure sensor on the sensing end measuring pressure pulses. Each positive pulse is a wheel travelling over the sensor.

  5. #5
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    Quote Originally Posted by BriComp View Post
    The systems used in the UK for temporary speed measurement consist of a rubber tube with one end (the far end) closed and I assume a pressure sensor on the sensing end measuring pressure pulses. Each positive pulse is a wheel travelling over the sensor.
    Thank you @BriComp.

    Yes, we sue that in the US too but it is bulky, cumbersome and is only for a temporary installation.

  6. #6
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    Jimmie:
    Why not use a small laser and a sensor at the other end?
    or,
    You could try two thin strips of aluminum foil very close to each other on a non conductive layer perhaps made of Capton or something like it. You could use perhaps a capacitive touch circuit, or a resistive touch circuit to detect the pulses.

    Regards,
    Ed

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