Pressure-Sensitive Conductive Sheet

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aj_smith9
 
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Pressure-Sensitive Conductive Sheet

Post by aj_smith9 »

I was looking at the Pressure-Sensitive Conductive Sheet (http://www.adafruit.com/products/1361) was wondering can i retrieve reading from this material of how hard the pressure is applied?

If not what can I use as I am looking for a material in which i can take reading of how much force is applied.

Thank you

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adafruit_support_bill
 
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Re: Pressure-Sensitive Conductive Sheet

Post by adafruit_support_bill »

The Velostat material is not going to give you much accuracy or resolution for measuring force. It is designed as an anti-static packaging material and the fact that it is (usually) pressure sensitive is a happy accident. Pressure response varies somewhat from sample to sample, but It is great for making very low-cost sensors for non-critical applications.

An FSR will give you much better resolution, but are not super accurate. http://www.adafruit.com/index.php?main_ ... e+resistor
They would be good for demonstrating relative changes in a force, but not for precise measurement.

What is your application?

aj_smith9
 
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Re: Pressure-Sensitive Conductive Sheet

Post by aj_smith9 »

Want to measure a impact of a punch, hoping to make gloves or pads which measure the impact force.

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adafruit_support_bill
 
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Re: Pressure-Sensitive Conductive Sheet

Post by adafruit_support_bill »

In that case, you should consider using an accelerometer. If you are punching an object of known mass (such as a punching bag) you can get a very accurate measure of the acceleration due to impact and derive the force from that. http://www.adafruit.com/index.php?main_ ... elerometer

aj_smith9
 
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Re: Pressure-Sensitive Conductive Sheet

Post by aj_smith9 »

how would the accelerometer work? Also, didn't the distanced need to be fixed when using an accelerometer? Is there maybe an email address i could talk to you through so i can discuss this idea more further.

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adafruit_support_bill
 
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Re: Pressure-Sensitive Conductive Sheet

Post by adafruit_support_bill »

The accelerometer measures the force due to acceleration. If you attach the accelerometer to the punching bag, it will measure the acceleration due to the impact of the punch. You don't need to know how far it moved, only the acceleration. From that you can back-calculate how much force it takes to accelerate the mass of the punching bag at the level measured by the accelerometer. That will be the force of the punch.

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Alouzi
 
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Re: Pressure-Sensitive Conductive Sheet

Post by Alouzi »

adafruit_support_bill wrote: An FSR will give you much better resolution, but are not super accurate. http://www.adafruit.com/index.php?main_ ... e+resistor
They would be good for demonstrating relative changes in a force, but not for precise measurement.
Interesting information. What kind of sensor would you recommend for a precise measurement of a force ? (In my case, the change in force is gonna be so slow that I won't be able to use an accelerometer, and measuring the force is the whole point of my project)

Thank you

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adafruit_support_bill
 
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Re: Pressure-Sensitive Conductive Sheet

Post by adafruit_support_bill »

For relatively static measurement of force, a strain-gauge is the way to go. This is what is used in electronic scales.

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Alouzi
 
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Re: Pressure-Sensitive Conductive Sheet

Post by Alouzi »

Thanks for your (very quick) answer... I had hoped a "strain gauge" would not be the answer as I don't expect any (measurable/interesting) deformation in my material. I'll have to find a trick around it...

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jctj
 
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Re: Pressure-Sensitive Conductive Sheet

Post by jctj »

I had a similar situation - I have a student measuring the force caused by heading a soccer ball (or another player...) and I am using a digital sensor. There were two solid candidates, one that had greater sensitivity but a smaller range, and the other with a large range but smaller sensitivity. You can read what I was told in: viewtopic.php?f=48&t=63562

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