How to Make a Ridiculously Cheap Analog Pressure Sensor

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Intro: How to Make a Ridiculously Cheap Analog Pressure Sensor

Tired of paying exorbitant amounts for a simple analog pressure sensor?  Well here is an easy smeasy way to make an incredibly cheap analog pressure sensor.  This pressure sensor won’t be terribly accurate in terms of measuring precise weight or things of this nature, though it can be calibrated somewhat and if you choose to coat it in something like Plasti Dip some of the variables such as humidity and the like can be minimized.  However, what this analog pressure sensor is best for is for creating things like bumper sensors that can read variable levels of pressure and various other touch / pressure sensor applications.   Find more interesting things like this in the How-to section of my website TodayIFoundOut.com


Materials:

  • 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
  • Wire
  • (optional) Plasti Dip Rubber Coating

 

Step 1: Step 1

Step 1:

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.

Step 2: Step 2

Step 2:

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: Step 3 (optional)

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.

Step 4: Test

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.

Find more interesting things like this in the How-to section of my website TodayIFoundOut.com

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    54 Discussions

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    dikshad4

    1 year ago

    Can u interface it with a Arduino?

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    AndreM49

    2 years ago

    Anyone knows where exactly I can buy those exact wires from? preferably a know local store?

    1 reply
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    wgriffithAndreM49

    Reply 2 years ago

    its solid copper. my guess door bell wire. you can get it at any hardware store.

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    BoazK

    3 years ago on Introduction

    Hello, I'm really new and I don't have a Multimeter. I found a really basic one.. is it enough for this type of sensor?

    https://www.sparkfun.com/products/12966

    It just doesn't have an auto ranging function.

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    N Squared

    3 years ago on Introduction

    I made a video on how to build this if anyone needed more detailed instructions:

    https://www.youtube.com/watch?v=BwjgX0kXCpo

    The foam used in this project says static dissipative foam, but the link is black conductive foam.. they have different properties. Which one is actually being used here? Thanks

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    Brain55

    3 years ago

    And happy new year

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    Brain55

    3 years ago

    And thanks for the great instructable and idea

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    Brain55

    3 years ago

    If I wanted to see if somebody stepped on it about how much would it go up, do I just connect the + wire to 5v and - wire to gnd on arduino, and to get a value from it what code would I put. I'm fairly new to arduino and am in the 10-13 years range it would be very helpful to me if I received answers

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    JeffreyH

    3 years ago on Introduction

    How could one use this to sense a peak pressure from a fast event? I've made several versions of an air-gun that shoots marshmallows. A chronograph doesn't give accurate data because the marshmallow changes shape in flight, but shows velocities > 400 mph. I had thought to use some sort of force sensor (trapped between 2 metal plates) to use the force of the smack of a marshmallow to stand in for velocity, but I can't figure out how to measure the peak force, which is applied over < 100 msec. My Fluke multimeter isn't fast enough. I know nothing about Arduino (I've tried reading websites, but the ones I've found assume you have basic Arduino knowledge), but I'd be willing to build something based on arduino, if instructions for absolute newbies are available. Thanks for the really cool idea.

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    cristiantuerca

    3 years ago on Step 4

    Wow, life is a every day learning. Thanks for sharing!

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    albenbrewder

    3 years ago on Introduction

    This application has a lot of potential, Next time I get some conductive foam I'll give it a try. However, there is one electrical circuit modification which may give better results... Use a "Kelvin" connection for the lead wires. In this way, the difference in contact resistance between your excitation leads and the foam is eliminated. To use, supply current to the foam through one pair of wires (low impedance) and read the voltage drop (high impedance) through another pair .

    To explain.. see Wikipedia

    http://en.wikipedia.org/wiki/Four-terminal_sensing

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    harristotle

    8 years ago on Introduction

    This is a great idea.
    In my hands, when I built a version that had the conductive foam sandwiched between sheets of aluminium (ie very good surface area), the resistance jumped around a lot, even when no force was applied or the same force was applied.

    I am wondering whether there is much difference between different types of conductive foam?
    Aren't they just graphite in polyurethane foam?

    Any ideas to make the sensor more stable?

    cheers

    2 replies
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    DonQuijoteharristotle

    Reply 4 years ago on Introduction

    you might have build a resonant capacitive circuit that picks up 50/60 Hz from the lines in your walls.

    i would put it in a resistor divider and look at the signal from it on an oscilloscope, or at least plot them with processing or something. if they fluctuate sinusoidally at 50/60 Hz, you found your culprit

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    harristotleDonQuijote

    Reply 4 years ago on Introduction

    Thanks DonQuijote, that is an astute comment.
    The problem is evident on a multimeter, set to resistance range, so I suspect not. I will have a look again though, with shielding. I also have some copper tape on order from China, and I'll try that to see if there is perhaps an "oxide layer" effect. (Knowing my luck, aluminium oxide will turn out to be piezoelectric !!! :{ )