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Measure time when ground connection is lost ?

Discussion in 'General Electronics Discussion' started by mascail, May 26, 2014.

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  1. mascail

    mascail

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    0
    May 26, 2014
    Hey,

    say a person is wearing a fitness wristband. This wristband is designed to measure the vertical jump height. Is it possible to measure the time as soon as the person jumps up, thus losing the connection to the ground? I thought of sending a small current through the person's body, if the current can flow freely into the ground, a circuit remains open and when the current can't flow into the ground anymore (so it's only flowing through the body), another circuit closes and stops the time. Then through a equation I can calculate the height. This needs to be automatic.

    thanks in advance!
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    I guess you could try using a conductive rubber pad on the sole of one shoe (or both shoes if you want to make sure both feet are off the ground) and a conductive rubber pad for the person to stand on... Your monitoring circuit would need a wire from the shoe and a wire from the pad on the floor.
     
  3. duke37

    duke37

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    769
    Jan 9, 2011
    I believe there are pads that can be placed to detect walkers. Using one of these would eliminate the need to wire up the victim.

    Trafic detection is sometimes done with a fluid filled tube and a pressure detector. Wahing machines have sensitive pressure switches to detect if the water level is correct.

    A sprung platform and a microswitch would do.
     
  4. mascail

    mascail

    8
    0
    May 26, 2014
    Yes these ideas would all work out but my project is very limited because the device has to be a wristband. Therefore I think sending a small alternating current like 0.5mA through the body would be the best solution. But I just don't know if and how it's possible??
     
  5. BobK

    BobK

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    Jan 5, 2010
    Your wristband, without any other connections to the body to ground, could only send current from one side of the wristband to the other.

    Bob
     
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