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Help about using weight sensor in a circuit

  1. Aug 2, 2015 #1
    I am designing a circuit, in this simple circuit, when a weight isn't applied, the switch will go off and the circuit won't work until a certain weight is applied, how can i design it?? i am totally new and doing this for a science club, i have never designed any circuits with censor. so please be elaborate in your description, if possible, please give a simple drawing of a possible design and i will modify it according to my need.

    Thanks.
     
  2. jcsd
  3. Aug 2, 2015 #2

    anorlunda

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    A search for "weight sensor" on Amazon.com returned 88,673 hits.
     
  4. Aug 2, 2015 #3

    berkeman

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    Staff: Mentor

    Try doing a Google Images search on Limit Switch:

    http://3.imimg.com/data3/YP/XH/MY-3059229/limit-switch-250x250.jpg
    limit-switch-250x250.jpg
    You could improve the Google Images search by adding the term Circuit to the end of it to get some typical schematics...

    :smile:
     
  5. Aug 2, 2015 #4

    jim hardy

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    Weight is force.
    One can buy force sensors.

    Force will compress or stretch a spring, changing force into movement.
    You could detect movement with a switch like the picture above
    or with the optical wheel sensor from a junkshop computer mouse

    to change force into movement with some accuracy,,
    check out Hooke's Law
    http://www.britannica.com/science/Hookes-law
     
  6. Aug 3, 2015 #5

    davenn

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    yup, commonly called Load Cells


    Dave
     
  7. Aug 4, 2015 #6

    meBigGuy

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    There are many approaches, some alluded to above. It depends a lot on your mechanical constraints, which you have not been clear about. Are you allowed to have something move, or does it have to be an essentially solid/steady platform? If it can move, how much?

    Putting rocks in a basket connected to a spring is a different problem from putting rocks on a tabletop that is essentially solid. Or are you pouring water is a bucket? Adding people to a platform? We have no idea.

    But is does boil down to either:

    a load cell (or strain gauge) that drives a detection circuit. This requires a load cell amplifier and comparator to drive a relay or something. Probably not what you want.
    OR
    a switch (mechanical or optical) that detects spring displacement (or the like).
     
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