- Any static dissipative foam (If you’ve ever ordered any IC chips, you probably have some lying around. IC’s are often set in this foam for shipping.) or if you don’t have any, you can pick it up from a variety of places, such as this
- (optional) Plasti Dip Rubber Coating
Cut the foam to the size you like. You can cut it quite small and still get a good range of resistance levels. The foam in this picture is cut to less than half an inch square and about 1/4 inch thick; once completed these two each produce a range of around 2.6K Ohms down to 400 Ohms when squished completely.
Poke two wires into the foam. Make sure the wires aren’t touching and there is a bit of a gap between the two so that when squished they won’t touch. To make sure the wires don’t come out while in use, I poked the wire all the way through and bent them at the ends.
Step 3 (optional):
At this point your new analog pressure sensor is all ready to use. However, I like to put a nice covering on it to protect it from wear and tear and a little electrical insulation might be needed depending on what you are going to use this for.
My preferred method of covering the sensor is to use Plasti Dip or equivalent liquid plastic coating. If using Plasti Dip, dip once slowly and hang the sensor to dry. Wait 20 minutes and do this again. That should give a nice thick coat on the sensor. The Plasti Dip will stiffen the sensor quite a bit, so don’t put too much on if you want it to stay extra squishy. In this case, one coat is probably enough. Play with it to get it to your liking for your particular usage.
Alternatively, you can just wrap it in electrical tape or equivalent, but I’ve found that tends to not hold up well over the long haul. It also carries the potential bad side effect of the adhesive on the tape causing the foam to not be able to re-expand over time and thus ruin the pressure sensor. Plasti Dip doesn’t seem to have this problem in the sensors I’ve made.
I’ve also tried using a little bit of visqueen cut and wrapped over the pressure sensor and sealed around it. This worked pretty well. And of course, you could just not put any covering on it at all if you aren’t worried about electric shock in the usage you are using these for.
That’s it. At this point, test it on your multimeter, if you have one. You should see a nice range of resistance depending on how hard you are pressing or not. If necessary, you may want to hook up a resistor with this depending on your usage.
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- I wish I could remember where I learned this. I picked it up in an electrical engineering textbook I read a few years back when I got really in to learning electrical engineering. But, I can’t remember what textbook it was in and can’t seem to find a reference anywhere to this handy little trick for making a cheap analog pressure sensor. If anybody knows an electrical engineering book that mentions making an analog pressure sensor this way, please let me know so I can cite it here.