Electronics force sensors, any help

Discussion in 'Modding' started by h_2_o, 11 Jul 2006.

  1. h_2_o

    h_2_o What's a Dremel?

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    I'm looking for something similar to these made by phidgets

    http://www.phidgets.com/index.php?m...=itemview&KID=115260445212.218.211.146&IID=76

    however i am looking for something that can handle several hundred lbs.

    as for the application, well it is kinda simple and going for a good cause. For people with congestive heart failure to determine how much water they are carrying they weigh themselves daily to see how they need to do thier medication with water pills. However there are those that can not get out of bed, and beds that have built in scales are freaky expensive. so a few of us are looking at trying to build something with 4 pads so that a bed can be wheeled over the pads hooked up to a laptop and weigh the person. basically it would be "bed + person - original bed weight" on a daily basis. anyway if anyone has any ideas on a cheap force sensors that might be easily integrated it would be appreciated.
     
    h_2_o, 11 Jul 2006
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  2. emady

    emady What's a Dremel?

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    emady, 11 Jul 2006
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  3. Glider

    Glider /dev/null

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    You could just use 4 normal balances? They don't cost that much...
     
    Glider, 11 Jul 2006
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  4. h_2_o

    h_2_o What's a Dremel?

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    when you say 4 normal balances i'm not really sure what you mean by that, can you be more specific?

    thanks
     
    h_2_o, 11 Jul 2006
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  5. wajt

    wajt What's a Dremel?

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    i think he means 4 normal scales
     
    wajt, 11 Jul 2006
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  6. Glider

    Glider /dev/null

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    Yes :) that I meanth :D
     
    Glider, 11 Jul 2006
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  7. Rod10k

    Rod10k What's a Dremel?

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    Yep, you could even get four digital scales, remove the displays and hook them into a uC with a single display.
     
    Rod10k, 11 Jul 2006
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  8. h_2_o

    h_2_o What's a Dremel?

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    that will work for the short term, however i am still looking for a more elegant solution for a long term fix
     
    h_2_o, 12 Jul 2006
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  9. ConKbot of Doom

    ConKbot of Doom What's a Dremel?

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    could you possibly use springs of a known strength, and use the amount of deflection in them to gauge weight? I know its possible, but I dont know to what accuracy.
     
    ConKbot of Doom, 13 Jul 2006
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  10. elctroJunky

    elctroJunky What's a Dremel?

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    Higher weights normally aren't measured directly by putting the weight onto a sensor.
    You normally have a cylinder (or four at each corner one) that is equipped with stretch sensors. If a weight is laid onto that cylinder the cylinder is being compressed. This compression is typical for a given weight on a cylinder of given material and size.
    The compression is measured by the stretch sensors, the attained values can be calculated into the actual mass that is applied onto the cylinder.
     
    elctroJunky, 14 Jul 2006
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  11. nleahcim

    nleahcim What's a Dremel?

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    I think some FSRs (force sensing resistors) can handle the task. A quick google turned up this one that can do 100lbs. Good luck!
     
    nleahcim, 15 Jul 2006
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  12. 0013

    0013 What's a Dremel?

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    100 lbs * 4 makes 400lbs (~ 180 kg)

    a decent 1 person bed( especially adjustable beds) might already make half of that weight, add a heavy person and you're overloading those :eeek:
     
    0013, 15 Jul 2006
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  13. elctroJunky

    elctroJunky What's a Dremel?

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    I agree... and note, sensors shouldn't be driven to their max. as they tend not to be very precisely at the maximum they can handel.
    Of course you could use more than 4 sensors...
     
    elctroJunky, 15 Jul 2006
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