Instructables
Picture of Conductive Fabric Pressure Sensor
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Sew together conductive fabric and anti-static plastic to make your own fabric pressure sensor!

These step-by-step instructions will show you how to make your own fabric pressure sensor. It mentions two different variations, depending on if you use stretchy or non-stretchy fabric.
The materials used for the sensor are basically cheap and off-the-shelf. There are other places that sell conductive fabrics and Velostat, but LessEMF is a convenient option for both, especially for shipping within North America.

Velostat is the brand name for the plastic bags in which sensitive electronic components are packaged in. Also called anti-static, ex-static, carbon based plastic... (So you can also cut up one of these black plastic bags if you have one at hand. But caution! Not all of them work!)

To make the sensor fully fabric one can use EeonTex(TM) conductive textile (www.eeonyx.com) instead of the plastic Velostat, but at the moment EeonTex(TM) conductive textile is only available in a minimum of 100yds.

This is an improvement on the Flexible Fabric Touchpad Instructable, using "iron-on" and plastic ex-static instead of the fabric which is less stable in maintaining resistance between the two conductive layers.

To see what we use this technology for visit:
www.massage-me.at
www.plusea.at
www.kobakant.at

VIDEO


 
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Step 1: Materials and tools

Picture of Materials and tools
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MATERIALS:

Stretchy version:
- Cotton jersey
- Stretch conductive fabric from http://www.lessemf.com
also see http://cnmat.berkeley.edu/resource/stretch_conductive_fabric
- Fusible interfacing from local fabric store

Non-Stretchy version:
- Cotton
- Shieldit conductive fabric from http://www.lessemf.com
also see http://cnmat.berkeley.edu/resource/shieldit_super
it already comes with heat glue fused to one side

Both versions:
- Velostat by 3M from http://www.lessemf.com
also see http://cnmat.berkeley.edu/resource/velostat_resistive_plastic
- Thread
- Machine poppers/snaps

TOOLS:

- Pen and paper
- Ruler
(- Compass)
- Scissors
- Iron
- Sewing needle
- Popper/snap machine (hand held or hammer and simple version)

Step 2: Stencils

Decide on a shape for your pressure sensor. Consider that you will need to create two separate tabs for the two layers of conductive fabric and that these should not touch each other (see pictures).

Fabric: sketch the shape for your sensor onto some paper or cardboard, including both tabs.
Velostat: create a 5mm smaller version of this shape, not including the tabs.
Conductive fabric: create a 10mm smaller version of the fabric shape that only includes one of the tabs. If your shape is not symmetrical you might have to create two stencils for this part.

Thrace these stencils to the fabrics and cut out the correct number of times:
2x Fabric, 2x Velostat, 2x Conductive fabric

If you are working with stretchy fabric and thus stretch conductive fabric or any other kind of conductive fabric that does not already come with fusible attached, you will want to fuse (iron-on) some interfacing to it before you trace ad cut out your shapes.

Step 3: Ironing-on (Fusing)

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Now that you have all of the shapes cut our of the fabrics you ill need. You can fuse (iron-on) the conductive fabric to your fabric pieces (see pictures).

Also, if you are working with stretchy fabric you will want to cut two small pieces of non-stretch or thicker fabric the size of your tabs and fuse these to your tabs so that when you punch the poppers through, the stretchy fabric does not damage when stretched.

Step 4: Sewing

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Sandwich your piece of Velostat between your two pieces of fabric fused with conductive fabric, so that the conductive fabric faces inwards, towards each other, separated only by the Velostat.

Thread a needle with regular thread and stitch around the edges. Or if you have a sewing machine, you can also use this.

Step 5: Poppers

Read the instructions on how to use your popper machine. Attach a female popper to one side and a male popper to the other, preferable facing the same side.

Step 6: LEDs and vibration motors

To see how your pressure sensor works we will need to include it in a simple electronic circuit.
If you happen to be working a lot with poppers and circuits you might like to modify a set of crocodile clips to have poppers on one end. Otherwise you can just clip on to the poppers.

To visualize with a multimeter, create the following setup (see pictures and video):
Set multimeter to measure resistance (in Ohm), should be between 2 K Ohm - 10 Ohm for stretch conductive fabric and X - 200 Ohm for Shieldit conductive fabric. Of course this depends on the size of your conductive surfaces and how tight the initial pressure from your stitching around the edge is.
Attach the multimeter plus to one side of fabric pressure sensor (doesn't matter which side) and multimeter minus to other side of fabric pressure sensor. Apply pressure and watch the resistance value change. You might have to adjust the range if you don't see anything. If you have a constant connection then either you forgot to put the Velostat in between or somewhere your two pieces of conductive fabric are touching.

To visualize with LED or vibration motor, create the following setup (see pictures and video):
Connect the plus of a 9V battery to one side of the fabric pressure sensor (doesn't matter which side) and connect the other side of the pressure sensor to the plus of an LED or either side of the vibration motor (switching plus minus only affects the direction of the vibration motor, whereas an LED only works in one direction). Connect the minus of the LED or the other other side of the vibration motor to the minus of the 9V battery.
Apply pressure to the fabric pressure sensor and control the brightness of the LED or the strength of the vibration.

To visualize with microcontroller and computer:
For Arduino microcontroller code and Processing visualization code please look here >> http://www.kobakant.at/DIY/?cat=347


Videos




ENJOY!
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eklypz5 months ago

Do you happen to have any suggestions on how to make this waterproof? I would like to use this to put sensors around a dance floor that people step on and interactively control neopixels or some other lighting effect but think the fabric would get tore up or drinks spilled on. Thanks for any advise!

richddt1 year ago
I'm also interested in making a larger one, about 19" x 9". Did you determine if the resistance changes? I'm just looking to make a switch, so perhaps there's an even easier way to do it.
billlavin1 year ago
I would love to know if anyone can help me here.... I want to find a senser for persperation fabric company that makes these kinds of fabrics so I can contact them for a special project I am working on... my e-mail is: bill.lavin@verizon.net Thanks so much...
lnorooz1 year ago
Tooootally awesome!

I've got a question for you. I want to do this on a slightly larger scale. If I wanted to make this in the dimensions of around 3x3 feet, how would that affect the resistance? Would I have to push down harder to get it to work? Also, how would a 6x6 feet piece of this work? Would it be twice as hard when I push down on it?
mrmerino2 years ago
Could I rotate the connectors so they're closer to each other?
Plusea (author)  mrmerino2 years ago
yes, sure! just make sure the conductive opposite sides of conductive fabric never touch each other directly. only ever through the velostat.
great job.
freak882 years ago
Hey. This is great! I was planning on purchasing this pressure sensor. Just had a few questions -
1. What is the range of force that it can measure? ( If analog values of the force can be tapped from it at all!)
2. Can the surface area be made smaller?
3. Does the pressure sensing work on both sides of the material?

Thanks in advance :).
TSLoire2 years ago
Wow Plusea this is awesome! Infact it's just what I have been looking for! A few questions if you'd be so kind to answer?

Firstly, instead of using batteries as a power source, would it be possible to use a USB power source? For example, you plug such a device as this into the PC using a standard USB cable?

I am creating a touch sensitive project right now and I think this design is awesome, if it would take power from a USB connection then I'd be hooking up the wires to pins on a U-HID G board (http://www.u-hid.com/home/uhidg.php) and using the touch/pressure as input. Any ideas on whether this would be possible or not?

Thnaks, I'm going to have a gander at your other projects =) Hope to hear from you soon!
hazykev TSLoire2 years ago
That's totally possible - USB is runs at 500mA &has 0V & 5V pins so it's possible to use it as a power supply for all kinds of things, provided of course the G board (which I'm not familiar with) will work @5V, <500mA
rmohamed12 years ago
hi..first, i would like to say that ur idea is really cool..n amazing..
anyway, o want to make something similar, but cant find the materials here.im in Malaysia..would you know of the closest place i could find something suitable..any alternative?
awaiting ur reply..
thanks
spost3 years ago
Great work! I think that your device may be helpful in a project I am working on. I am trying to find a pressure sensor that can monitor the pressure between a child's heel and a cast. That is, if the pressure becomes too great, parents are signaled by illumination of the bulb and the child can be repositioned etc. A couple of questions: 1) Do you think your product will work for this application? 2) I would need to minimize things like alligator clips close to the sensor as they would be in the cast and potentially harmful to the patient's skin. So, is it possible to extend the "wings" so they would be outside the cast? 3) Casts often stay on for many weeks. Are the materials durable enough to hold up?
Thanks so much!
Plusea (author)  spost3 years ago
for sure you can extend the tabs, you can also replace the alligator clips with strips of conductive fabric or thread. i think the challenge will be to calibrate the pressure sensor to detect what is too much pressure and compensate for any change in the sensor range that would occur over time and under constant pressure. but i think it would be possible and would love to see what you make!
Hlias3 years ago
Very good instructable indeed. Congratulations and thank you very much for your post.
I just finished making the pressure sensor successfully and i tried to connect it to a small circuit, in order to control a small coin-type vibrator. What happened when I connected the vibrator, was that even without pressing the switch, the vibrator went on (although not very strong) while when I pressed the switch it vibrated more intensely.
I would like the switch to be like on/off type (hence switch). What I realized is that the resistance provided by the sensor is very low (around 130 Ohms as I measured it) and thus permits current flowing even when in the "off" position.
Is there any solution to my problem (like a small circuit maybe with a transistor)?
Plusea (author)  Hlias3 years ago
good question. the resistance of the pressure sensor depends very much on the construction. if you manage to sandwich and sew it together really loosely you can sometimes create high enough resistance for vibration motors and LED lights to appear 'off'. but not wanting to rely on loose construction is probably a better way to go and the easiest solution i see is to combine the pressure sensor with the fabric switch - so add a layer of perforated foam in between one side of the velostat and conductive fabric! the layer of foam will insure that there is no contact unless pressured and then when pressured the pressure sensing properties of the velostat will apply.

fabric button >> http://www.instructables.com/id/Three-Fabric-Buttons/
lanehogenes3 years ago
I have a simple question. What is the fusible interfacing material exactly? Is there a name for this product that I can go search for? I'm just not sure exactly what this stuff is and what it does. Is it a conductive fabric? Thank you for all your great help!
Plusea (author)  lanehogenes3 years ago
here is a link to a description of what fusible interfacing is:
http://www.fabriclandwest.com/Notion_basics/Interfacing/interfacing.htm

it is basically a thin sheet of glue that melts when heated by the iron and is intended to "fuse" (=glue) two layers of fabric together.
Thank you!
Sapas_3 years ago
Hello everyone.
I'm currently working with a velostat equivalent, Linqstat, from Caplinq. Does anyone have a suggestion on how to characterize this material? Electrically, I mean.

Thanks in advance!
Plusea (author)  Sapas_3 years ago
Linqstat is basically identical to Velostat (they are just two different brand names). They are both carbon infused polymers and have "piezo-resistive" electrical properties.
caplinq4 years ago
Hi Plusea - We have some people asking which hot melt adhesives work best with the Linqstat / Velostat material.

Knowing that you probably have more experience than anyone with bonding and working with these materials, I was hoping you could provide some guidance.
Plusea (author)  caplinq4 years ago
i've actually experienced that heat ruins the piezoresistive properties of velostat.
so i would tend to recommend double sided sticky tape instead.
caplinq Plusea4 years ago
Thanks Plusea - yes, the softening temperature of the Linqstat is around 85C, so I would agree that if a hot melt is used, that the temperature of the hot melt is less than the softening temperature of the Linqstat.
drummerwei4 years ago
Hi, I am a graduate student in Taiwan. Your Idea is really AMAZING, I LOVE IT ! Would you mind I ask you some question about the Velostat. Can you tell me the Velostat datasheet, Thickness and Resistance Value ? Because I have found the Velostat in Taiwan, but the Resistance was too high approaching 1 x 10^7 ohms, it is very hard to used.Or maybe I can use some conductive foam according your method?I'm just confused on the resistance. Hope you can help me to solve this problem.Your help and early reply will be appreciated. I am looking forward to hearing from you soon.
Plusea (author)  drummerwei4 years ago
i use the brand products velostat (3m) and linqstat (caplinq) and these have a good resistance range. from K ohm to hundred ohm. here is my post on velostat: http://www.kobakant.at/DIY/?p=381
andresjv224 years ago
HI PLUSEA!! Excuse me, I want to make your pressure sensor, but I have some questions that stop me... 1. In this one you actually don't use a conductive thread, do you? 2. The conductive fabric is a special one? Or maybe with nylon o polyester that produce static is possible? 3. Would you say that without Velostat or that kind of bag, this experiment is impossible? I'm surprised because first of all, isn´t that material specially not for conduct? Why with pressure it changes? Congratulations for your work and thanks in advance for your answer!!
Plusea (author)  andresjv224 years ago
i'm not quite sure i understand everything you are asking. but will try to answer. please ask again if i am still not clear. you can use any kind of conductive material on either side of the velostat (piezoresistive material). but the more conductive the material is, the less range you will have. that is why in later versions i switch to using conductive thread - to minimize the conductive surface area. the velostat or any other piezoresistive material is key to this pressure sensor working.
kewlkat0074 years ago
 i love this you could take this next level and make bracelets if  you you configure some type of batery pack or some thing in there like lilly pad but any ways this is great already made one
knektek4 years ago
lol. Put this on your sofa, when you sit down it will light up. Now that will explain the wall wart coming out of the sofa.....
zigzagchris4 years ago
I see it now. underwear that weighs you when you sit down. Mabee it could incourage weight loss?
zyzar4 years ago
Hi

I would like to know that can it be tested with 1.5V battery with simple LED??
Plusea (author)  zyzar4 years ago
if you have an LED that lights up with a 1.5V battery (without pressure sensor), then it might. otherwise put two 1.5V batteries in series or use a 3V coin-cell battery and this should definitely work.
if you connect it all together with the sensor and the LED is always on, then it could be that your pressure sensor is so tight that the initial pressure is already enough to decrease the resistance of the velostat to fully power the LED, but this does not mean that your sensor does not have any range. just that it is the wrong range (too low resistance) for the LED.
hope this helps.
bartens6 years ago
Hi can anyone supply me with 6 of thos wonderfull flexible fabric pressure sensors? I have tried myself but cannot get hold of the right material here in The Netherlands, Europe. If someone can help me get the right fabrics this might help too.. Thanks
caplinq bartens4 years ago
You can buy LINQSTAT (equivalent 3M Velostat material) directly from our website and it ships from either our Ottawa, Canada or Amsterdam Netherlands warehouse depending on where you ship to.
http://www.caplinq.com/linqstat-vcf-s-series-linqstat-volume-conductive-film.html

Plusea (author)  bartens6 years ago
I'd be happy to send you some. I'm also selling be happy to send you some. I'm also selling Fabric Bend Sensors via Etsy >> http://www.etsy.com/view_listing.php?listing_id=14491554

Regarding finding conductive fabrics in Europe... I'm looking into it. But LessEMF also ships to Europe.
_si_ Plusea5 years ago
I've just had LessEMF ship to the UK and it arrived in under a week...
caplinq5 years ago
We are happy to support these efforts too and can supply a conductive Velcro, and possibly conductive fabric along with the 4mil (0.1mm) and 8mil (0.2mm) conductive LINQSTAT material. Send an email to info@caplinq.com and I will ask that these requests are forwarded to me. Chris Perabo, CAPLINQ Corporation
caplinq caplinq4 years ago
I noticed that people were asking if they could get this conductive plastic in Europe or Canada.

CAPLINQ offers an equivalent to 3M Velostat (http://www.caplinq.com/linqstat-vcf-s-series-linqstat-volume-conductive-film.html). It's essentially the same conductive plastic but without the brand name. You can buy it directly from our website and it ships from either our Ottawa, Canada or Amsterdam Netherlands warehouse depending on where you ship to.
Please give any suggestion to the "Instructables the Movie" at http://www.instructables.com/community/Instructables-the-movie/
caplinq5 years ago
(removed by author or community request)
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