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HELP!! Force Sensing Resistor

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  • adamcareyou
    Hi, I was planning make a hand with Servo and Force Sensing Resitors and found some Force Sensor Resistors (Interlink Electronics) with reasonable price.
    Message 1 of 5 , Nov 20, 2004
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      Hi,

      I was planning make a hand with Servo and Force Sensing
      Resitors and found some Force Sensor Resistors (Interlink
      Electronics) with reasonable price.

      Please help me to check whether this sensor is good enough
      to make the hand.

      http://www.drrobot.com/products_item.asp?itemNumber=FSR400

      Thanks!

      Adam
    • Terry Slocum
      Adam, These look like cool little sensors. I may get a pack just to experiment with. I m still trying to get a handle on what you are trying to do. I assume
      Message 2 of 5 , Nov 22, 2004
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        Adam,

        These look like cool little sensors. I may get a pack just to
        experiment with.

        I'm still trying to get a handle on what you are trying to do. I
        assume the FSR's are to be used as fingertip sensors. How are you
        planning on connecting the feedback loop between the FSR and the
        servo?

        The amount of force you want to use to pick up and hold an object
        depends on the weight, texture, and delicacy of the object. The
        design of the hand can also have a significant effect. By my
        calculations the minimum force that these sensors are designed to
        detect is over 5/8 of a pound. Does this sound reasonable for your
        application?

        Terry


        --- In sfrsa@yahoogroups.com, "adamcareyou" <adamcareyou@y...> wrote:
        >
        >
        > Hi,
        >
        > I was planning make a hand with Servo and Force Sensing
        > Resitors and found some Force Sensor Resistors (Interlink
        > Electronics) with reasonable price.
        >
        > Please help me to check whether this sensor is good enough
        > to make the hand.
        >
        > http://www.drrobot.com/products_item.asp?itemNumber=FSR400
        >
        > Thanks!
        >
        > Adam
      • LJGeib@aol.com
        Terry, I get a bit less as the minimum force sensitivity. As I read the data sheet, the force sensitivity range is 100N from
        Message 3 of 5 , Nov 23, 2004
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          Terry,
          I get a bit less as the minimum force sensitivity.
          As I read the data sheet, the force sensitivity range is  <1N to  >100N
           
           
          "Force is defined by Newton's second law as the product of mass and acceleration (F = m x a). The unit of force using the International System of Units (SI) or the metric system is the newton (N). ("Newton" is usually written as a lower-case word even though it is named after Sir Isaac Newton.) Mass is measured in kilograms (kg), and acceleration is measured in meters per seconds squared (meters/seconds2), such that 1 N = 1 kg x 1 m/s2."
           
           
          if you substitute 9.8 m/Sec^2 for "a" in the equation ( acceleration due to gravity), I get a force equivalent to placing slightly over  a 102g  mass on the sensor as the minimum force, or about 3.6 ounces (at 28 g/ oz)
           
          If you somehow arranged to measure pressure instead, the claim is 1.5psi to 150psi. since the sensor only has an area of .04 sq.in, that should give a sensitivity of  .06 lbs (a bit over twice that if they are counting both sides of the sensor). That's one or two ounces.
           
          These measurements don't seem to jibe, so I question exactly what the data sheet is saying, especially since it says the device turn on force is 20g to 100g. (.7 to 3.57 oz)
          Maybe they are just trying to say the devices vary a lot.
           
          they are all under your 5/8 lb figure, though
           
          Larry
           
           
          In a message dated 11/22/04 10:17:30 PM Pacific Standard Time, sfrsa@yahoogroups.com writes:

          Adam,

          These look like cool little sensors. I may get a pack just to
          experiment with.

          I'm still trying to get a handle on what you are trying to do. I
          assume the FSR's are to be used as fingertip sensors. How are you
          planning on connecting the feedback loop between the FSR and the
          servo?

          The amount of force you want to use to pick up and hold an object
          depends on the weight, texture, and delicacy of the object. The
          design of the hand can also have a significant effect. By my
          calculations the minimum force that these sensors are designed to
          detect is over 5/8 of a pound. Does this sound reasonable for your
          application?

          Terry

        • LJGeib@aol.com
          Terry, depending what measure you use from the data sheet, the force the sensor will measure seems a bit less. According to the datasheet, The minimum force
          Message 4 of 5 , Nov 23, 2004
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            Terry,
             
            depending what measure you use from the data sheet, the force the sensor will measure  seems a bit less.
             
            According to the datasheet,
             
            The minimum force sensitivity is given as 1 newton, or the force equvalent to about a 3.6 oz. weight placed on the sensor.
             
            The minimum pressure sensitivity is 1.5 psi. Since the area of the sensor is .04", that should give a force of around.06 lb, or about 1 oz. --> Twice that, if they figure both sides of the sensor.
             
            the minimum turn on force is given as  20 to 100 grams. (0.7 to 3.57 oz) .That about brackets the above figures.The range may be for the differentsize devices., the 400 being the smallest(biggest turn on force, or smallest?)
             
            I'm not exactly sure how the datasheet writers took their measurements, but they are all under your 5/8 lb ( 10 oz) figure.
             
            Larry
             
             
            In a message dated 11/22/04 10:17:30 PM Pacific Standard Time, sfrsa@yahoogroups.com writes:
            Message: 1        
               Date: Tue, 23 Nov 2004 06:07:49 -0000
               From: "Terry Slocum" <tslocum@...>
            Subject: Re: HELP!! Force Sensing Resistor


            Adam,

            These look like cool little sensors. I may get a pack just to
            experiment with.

            I'm still trying to get a handle on what you are trying to do. I
            assume the FSR's are to be used as fingertip sensors. How are you
            planning on connecting the feedback loop between the FSR and the
            servo?

            The amount of force you want to use to pick up and hold an object
            depends on the weight, texture, and delicacy of the object. The
            design of the hand can also have a significant effect. By my
            calculations the minimum force that these sensors are designed to
            detect is over 5/8 of a pound. Does this sound reasonable for your
            application?

            Terry

             
          • Terry Slocum
            The data sheet won t open for me right now, so I can t check my calculations. Looking back at my calculators log, I think I may have used the diameter of the
            Message 5 of 5 , Nov 25, 2004
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              The data sheet won't open for me right now, so I can't check my
              calculations. Looking back at my calculators log, I think I may have
              used the diameter of the pad as a radius. Thanks for correcting my
              mistake.

              Terry

              --- In sfrsa@yahoogroups.com, LJGeib@a... wrote:
              >
              > Terry,
              >
              > depending what measure you use from the data sheet, the force the
              sensor
              > will measure seems a bit less.
              >
              > According to the datasheet,
              >
              > The minimum force sensitivity is given as 1 newton, or the force
              equvalent
              > to about a 3.6 oz. weight placed on the sensor.
              >
              > The minimum pressure sensitivity is 1.5 psi. Since the area of
              the sensor is
              > .04", that should give a force of around.06 lb, or about 1 oz. --
              > Twice
              > that, if they figure both sides of the sensor.
              >
              > the minimum turn on force is given as 20 to 100 grams. (0.7 to
              3.57 oz)
              > .That about brackets the above figures.The range may be for the
              different size
              > devices., the 400 being the smallest(biggest turn on force, or
              smallest?)
              >
              > I'm not exactly sure how the datasheet writers took their
              measurements, but
              > they are all under your 5/8 lb ( 10 oz) figure.
              >
              > Larry
              >
              >
              > In a message dated 11/22/04 10:17:30 PM Pacific Standard Time,
              > sfrsa@yahoogroups.com writes:
              >
              > Message: 1
              > Date: Tue, 23 Nov 2004 06:07:49 -0000
              > From: "Terry Slocum" <tslocum@p...>
              > Subject: Re: HELP!! Force Sensing Resistor
              >
              >
              > Adam,
              >
              > These look like cool little sensors. I may get a pack just to
              > experiment with.
              >
              > I'm still trying to get a handle on what you are trying to do. I
              > assume the FSR's are to be used as fingertip sensors. How are you
              > planning on connecting the feedback loop between the FSR and the
              > servo?
              >
              > The amount of force you want to use to pick up and hold an object
              > depends on the weight, texture, and delicacy of the object. The
              > design of the hand can also have a significant effect. By my
              > calculations the minimum force that these sensors are designed to
              > detect is over 5/8 of a pound. Does this sound reasonable for
              your
              > application?
              >
              > Terry
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