How to use FSR to calculate the force?

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bluesky0215
 
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Joined: Fri Mar 27, 2015 3:26 am

How to use FSR to calculate the force?

Post by bluesky0215 »

Hello, I am doing a project which a FSR is used to calculate the force on the fingertip.

I used the code of calculating the force of FSR on adafruit :
https://learn.adafruit.com/force-sensit ... ing-an-fsr

I would like to know why fsrConductance is divided by 80 and 30:

Code: Select all

// Use the two FSR guide graphs to approximate the force
    if (fsrConductance <= 1000) {
      fsrForce = fsrConductance / 80;
      Serial.print("Force in Newtons: ");
      Serial.println(fsrForce);      
    } else {
      fsrForce = fsrConductance - 1000;
      fsrForce /= 30;
      Serial.print("Force in Newtons: ");
      Serial.println(fsrForce);            
    }
Does the code adapt to the force in range of 1 kg to 10 kg? Or only below 1 kg?
If I want to measure the force between 1 kg to 10 kg, how do I modify the code?
I would really appreciate the help. Thank you very much!

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adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Re: How to use FSR to calculate the force?

Post by adafruit_support_bill »

I believe those numbers were derived empirically from the graph on page 6 of the data sheet:
https://learn.adafruit.com/system/asset ... rguide.pdf
Note that the curve is not linear, and the different divisors are used to approximate the slope change in the lower part of the graph.

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bluesky0215
 
Posts: 4
Joined: Fri Mar 27, 2015 3:26 am

Re: How to use FSR to calculate the force?

Post by bluesky0215 »

Thanks for your reply.
However, I use the sensor FSR 400, not 402.
Can I use the table on page.6?
If not, how can I change my code?

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adafruit_support_bill
 
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Re: How to use FSR to calculate the force?

Post by adafruit_support_bill »

That data sheet applies to the entire 400 series.

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