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Topic: Force Sensitive Resistors that can measure the force of a punch (Read 3194 times) previous topic - next topic


So I have done a bunch of googling on the subject but want to get some input / direction from the forum. I want to build a device that I can place on a punching bag and measure and differentiate the force of someone punching or hitting it. Before you post a link to the Cassius project, I have read all about it and it seems pretty good but I have questions.

1. Has anyone built the FSR that the cassius project outlines and do they only measure a "hit" or can they differentiate between the power behind that hit. Example: If I tap the FSR does it give me a 10 and if I do a full punch it give me a 100? I don't care about real world accuracy, mostly just differentiation.

2. I ok with building my own FSR but I would like to start with something off the shelf so I can take one component out of the equation. Has anyone used the FSR from sparkfun? Like this one: http://www.sparkfun.com/products/9376. I have read some FSR break down quickly and don't like bending.

3. Are FSRs even used to measure this kind of impact force or just touch / step on/off forces? Am I just barking up the wrong tree with my approach? I have seen projects with accelerometers but I want something on the surface.

Thanks for the input.


May 22, 2011, 12:23 am Last Edit: May 22, 2011, 12:27 pm by Simpson_Jr Reason: 1
I have no experience with FSR's and unfortunately I can't find the link, but a while ago I saw a cheap FSR made of conductive foam. Most people here will know the black foam, it's usually used to stick chips in to prevent ruining them by electro static discharge during shipping.

The guy who wrote the article placed a  metal plate on top and one under it. By squeezing it the resistance between the plates changes.

I probably would start researching cheap options like that since forces while hitting/kicking a punching bag can get quite high. I must say I really have no idea what's available commercially, but like you I'd be afraid to buy one and ruin it in no time.

So far I've seen two types, rather stiff and more elastic foam. I'd guess... the stiff foam won't have a long life, but can't tell you which would be best (if it works). I'd probably cover the sensor with a thick layer to prevent dents in the metal (making it unreliable)/not need a first aid kit.

It would of course be fair to add some arms/servos/sensors giving the punch bag a chance to hit back :)

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