Velostat issue?

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westachio
 
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Velostat issue?

Post by westachio »

Hi all,

I purchased Velostat and conductive thread from Adafruit to complete the Firewalker LED shoe project.

I am following the guide and made the velostat sensors as outlined here:

https://learn.adafruit.com/firewalker-l ... ep-sensors

When I continue onto the next step and view the serial monitor on my computer I get all 0's from the monitor. I did ensure that the conductive threads are not touching and a thread is taped onto opposite sides of the velostat.

Upon troubleshooting, it appears that the velostat I have is very conductive - so much so that it will not allow it to act as a sensor. To test this theory, I took two separate pieces of velostat and taped one thread to each. When I view the serial monitor with this setup, if the two pieces of velostat are not touching I get readings in the 1000's.

If I lightly touch (no pressure really) the two pieces together it reads 0.


I then thought I may need to add more layers in between. I took the whole sheet I ordered and folded it up to make it thick. I then touched the two velostat pieces from above to each side of the "pad." Same results, as soon as the velostat is touched I get 0's.


Is it possible that the velostat I got is too thin or too conductive? Is there anything else I can do?


Thank you!

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adafruit_support_rick
 
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Re: Velostat issue?

Post by adafruit_support_rick »

Pressure sensing is an "off-label" use of Velostat. Sometimes we get a piece that doesn't work well. Please email [email protected] with a link to this thread for a replacement sheet. Ask them for a "tested" sheet of Velostat

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westachio
 
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Re: Velostat issue?

Post by westachio »

Thank you for the response! I will send them an email.

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NCBlender
 
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Re: Velostat issue?

Post by NCBlender »

Other that testing every section of a roll of Velostat, are there any indicators that would help when purchasing Velostat to make sure it would work for this purpose (as a pressure sensitive resistor)? Are there different brands of Velostat that work better than others?

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Franklin97355
 
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Re: Velostat issue?

Post by Franklin97355 »

Velostat is a brand name of 3M and there are other products that do the same but since it is not designed for this use there is no way of telling what would be better.

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NCBlender
 
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Re: Velostat issue?

Post by NCBlender »

Are there other commercially available products that are semiconductive for projects? (like foam sheets or other types of plastics?)

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adafruit_support_mike
 
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Re: Velostat issue?

Post by adafruit_support_mike »

There are many different kinds of force-sensitive resistors:

https://www.adafruit.com/?q=force-sensitive%20resistors

and for serious measurement there are load-cell sensors. Those tend to be hard to work with though.. the output varies by a few millivolts and has to be amplified precisely. Velostat is for low-precision, "the pressure just changed a bunch" applications.

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NCBlender
 
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Re: Velostat issue?

Post by NCBlender »

Thanks so much for that info!

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