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Vehicle sensor and GPS

Discussion in 'Sensors and Actuators' started by Thomas Bredman, May 23, 2016.

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  1. Thomas Bredman

    Thomas Bredman

    May 23, 2016

    Working on a project that involves a readily purchased vehicle sensor based on a magentometer.

    This magnetometer detects vehicles and transmitts the signal wirelessly to a receiver unit. 433Mhz I think.

    What I would like to do is connect a SPOT GPS tracker unit to the receiver unit so that when a signal is received from the transmitter at the receiver unit it activates a button on the GPS tracker.

    Traditionally the button requires a physical press for 3 seconds to activate.

    I have another unit someone made. I am trying to reverse engineer it but my crude attempts were not successful.

    I am sure that someone can help and is something simple I am missing out on.

    I can post pictures of the other units wiring if that helps


  2. davenn

    davenn Moderator

    Sep 5, 2009
    hi there Thomas

    welcome to EP :)

    lots more info on this would be helpful, else it's really difficult to offer any advice

    what is the purpose of this system ?

  3. Thomas Bredman

    Thomas Bredman

    May 23, 2016
    Hi, Thanks and you are correct.

    So the vehicle sensor I have is the Mightly Mule FM231.

    You will see that as a vehicle or ferrous object moves past the probe it disturbs the local magnetic field.

    This sends a signal to the transmitter that is connected to the probe.

    The signal is transmitted to the small receiver unit a distance away (think driveway alert, long driveway)

    The receiver unit receives the signal and activates a small green LED on the unit and sounds a buzzzer in the unit to let you know and see (the LED) that someone is coming up your driveway.

    I want to take this a step further as I have a need for a remote location detector where there is no cell connection etc.

    Hence the connecting of the SPOT GPS tracker to the wireless receiver.

    Once a signal is received on the receiver it activates the location button on the GPS tracker unit.

    This in turn sends a email from a back end internet based system to the notification list.

    Here you will see the wiring connected to another unit I have.


    The bottom 2 wires are soldered to the USB power connection. So one is positive and the other negative.

    Not hard there. The top wire soldered to the unit has to be the wire that activates a button normally found on the front of the tracker. The button is an OK button and sends a signal to the GPS then to ground that sends a preformatted email to persons.

    Was designed for hikers to check in with family from remote locations.

    So what I am trying to figure out is how to connect this type of tracker to the receiver unit I have and have the signal activate the above function.

    The unit I currently have is not wireless and connected directed to the GPS tracker via a relay board.


    If you need anymore let me know

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