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FSR question about force and pressure
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FSR question about force and pressure

by nessimdave on Thu Oct 21, 2021 2:24 pm

Hi all,
I have an round pad FSR connected to an Arduino and a RGB LED. When the FSR has no force the blue illuminated then as force is applied it will go to green then red.

This works great when I squeeze with my finger but when i put it into my applcaion the force i am testing is a very small metal probe.
I don't seem to get the same results so I was wondering if there is a minimum area that will be needed to get a accurate reading ?
this must be some specification of how much square area must be used to acurately measure

For reference I have a small round FSR and my probe is about 2 mm ? Is that too small ? is there a better sensor I should get.
Let me know your thoughts,
thanks

nessimdave
 
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Re: FSR question about force and pressure

by adafruit_support_bill on Thu Oct 21, 2021 2:39 pm

If you look closely at the face of the sensor, you will see that there are interleaved traces connected to the two leads of the device. At a minimum, your actuator needs to press two adjacent traces onto the conductive film below to register any pressure at all. To register higher pressures, you need to have more surface area in firm contact with the conductive film. It may help to add a pad of stiff material between your probe and the sensor to distribute the force over a wider area.

Image

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Re: FSR question about force and pressure

by jps2000 on Thu Oct 21, 2021 8:35 pm

These devices are more indicators than measurement devices.
However, I achieved quite good results by having the sensor placed between two about 2-3mm thick pieces of fell. (Such things you glue on the legs of a chair to protect wooden floors). You can glue these fell pieces on metal or hard plastic cylinders that are mounted / guided parallel.
Then you get a rather good reproduceable force/ resistance characteristic.
Note: For a linear force/ voltage characteristic you need a current source.

Do not glue something on the sensor directly. It is important to have the force distributed evenly over the sensors surface.

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Re: FSR question about force and pressure

by nessimdave on Fri Oct 22, 2021 5:52 am

thanks for your suggestion i am going to try this.
Dave

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Posts: 4
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Please be positive and constructive with your questions and comments.