pull potentiometer???

Discussion in 'General Electronics Chat' started by villapanama, Jun 13, 2016.

  1. villapanama

    Thread Starter New Member

    Jun 13, 2016
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    hi,
    i am looking to hopefully develop and idea into a tangible demo.
    i am looking for a part which I dont know the proper name for.

    I am looking for a pot or a small device that would give a resistance (preferable) or a voltage as it is pulled. i am looking some somehing that can handle anywhere from 50 to 200lbs.

    i guess this should be a comercially availalbe part as probably all of the digital hanging scales should use something similar.

    it would be ideal if the part:
    was spring loaded - or returned to its resting place when no force was applied to it.
    should be able to handle a dead weight of min 50lbs would. be nice it it. was 100lbs
    if it has an "in-line" design it would be better

    thanks for the help
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    A load cell?
     
  3. villapanama

    Thread Starter New Member

    Jun 13, 2016
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    I looked at load cells but from what I can see they record push weight sort of like a traditional scale, I a, looking for something that records pull force.

    ill look again into load cells
     
  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Look for tension load cell.
     
  5. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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  6. wayneh

    Expert

    Sep 9, 2010
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    There are also curvature sensors that can be set up to measure deflection of a rod, for instance, if you want to measure a force applied to the rod.

    But yes, all you need is a tension load cell.

    If it was me, I'd get a cheap bathroom scale and hang a harness off of it, so that a pull on the harness appears as weight on the scale. That's how we used to weigh our giant pumpkins back home. They're too big and awkward to place on a scale directly.
     
  7. joeyd999

    AAC Fanatic!

    Jun 6, 2011
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    You might also consider a simple spring and an LVDT. If you are handy, you could even wind one yourself.
     
    atferrari and cmartinez like this.
  8. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    You could also have a spring and a length of rope going round a pulley connect to a pot as a DIY version, but OP wants off the shelf.
     
  9. Tonyr1084

    Active Member

    Sep 24, 2015
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    Interesting concept. If I wanted to do this I'd go to my bag of tricks (Junk box) and grab one of those sliding pots I scrapped out of an old treadmill. Put a light spring to return it to the zero point and use a small cable to connect it to the end of a spring that was rated to handle the weight load you want. Of course it would be everything BUT calibrated, and I don't know if spring tension is linear or logarithmic, but it would be an interesting learning process.

    Use the slider pot as a voltage divider and use an Op-Amp to tailor the output.

    Well, that's what I think I'd do if I wanted to do what you propose. Like I said, not "Accurate" but if you merely want a reference or comparison it should be fairly meaningful.

    Oh, and those sliding pots from a treadmill, they're about 3 inches long, so it should allow you to have some sort of useful range - depending on the spring holding up the load.
     
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