Conductive Fabric Pressure Sensor

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

Step 1 Materials and tools

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)

Comments

[TSLoire]

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!

[rmohamed1]

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

[spost]

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]

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!

[Hlias]

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]

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/

[lanehogenes]

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]

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.

[lanehogenes]

Thank you!

[Sapas_]

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]

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.

[caplinq]

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]

i've actually experienced that heat ruins the piezoresistive properties of velostat.
so i would tend to recommend double sided sticky tape instead.

[caplinq]

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.

[drummerwei]

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 methodI'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]

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

[andresjv22]

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]

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.

[kewlkat007]

 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

[knektek]

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.....

[zigzagchris]

I see it now. underwear that weighs you when you sit down. Mabee it could incourage weight loss?

[zyzar]

Hi

I would like to know that can it be tested with 1.5V battery with simple LED??

[Plusea]

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.

[bartens]

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]

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]

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_]

I've just had LessEMF ship to the UK and it arrived in under a week...

[caplinq]

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 [e-mail] and I will ask that these requests are forwarded to me. Chris Perabo, CAPLINQ Corporation

[caplinq]

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.

[theseventhsage]

Please give any suggestion to the "Instructables the Movie" at http://www.instructables.com/community/Instructables-the-movie/

[caplinq]

(removed by author or community request)

[Plusea]

This is GREAT news!
more info on Velostat/Linqstat here:
http://www.kobakant.at/DIY/?p=381

[missperovaz]

Hello Plusea, I'm Carol, from Brasil. I've been watching your videos, Instructables and your photos. I'm working with sensor, arduino for a dance company. I'm an electrical engineer. Besides all common sensors for temperature, humidity, force, I made some wearable sensor too, using copper tape from 3M. My problem here is that it's very difficult to buy e-textiles and different materials. I'd like to ask you, what advantage do you feel using conductive textiles and thread instead of using copper tape and wires. Flexibility?? Besides the question, I'd like to offer you my help as an engineer. It seems to me you don't need it, but if you need, just say me. I'm here, far but on line!!!! Thanks a lot, Carol

[a55b0t]

I stumbled on this and it helped me solve a big problem I have been having on my current project... so thanks! I am still trying to figure out a way to make the pressure range larger because it seems to offer almost no resistance with very little pressure. It's a great start though, so maybe I can even do it in software. :)

[Plusea]

You can try layering the Velostat and also exchanging the conductive fabric for stitches of conductive thread (reducing conductive surface) >>
http://www.instructables.com/id/Conductive_Thread_Pressure_Sensor/
Also, Eeonyx offers a nice range of anti-static fabrics that have higher resistance.
Hope this helps:-)

[a55b0t]

I tried stacking the velostat but I didn't notice much of a difference with a reasonable amount of layers. Luckily I ordered the fabric sample pack when I bought my fabric from LessEMF. I found that the EX-Static stuff works really well, and each layer you add makes a pretty big difference. I'll find out if it works larger scale when I get my package. Thanks again. :)

[Plusea]

i also tried the anti-static fabric at one point, but found that it was not as stable as velostat, especially when sewn inside layers, the pressure from sewing already caused it to trigger. but now i must try it again:-)

[idaholaura]

Since my antistatic bag I had did not work, I tried some other bags around and then on a whim, I tried dryer sheets instead of Velostat, and lo an behold, dryer sheets work! Awesome if you want to try it out without waiting for shipping. Check out this instructable for how to make your own conductive fabric and you don't have to make any online orders. http://www.instructables.com/id/SEOH3GFFABRWUOD/

[Plusea]

Interesting. I did not know what dryer sheets were so i looked it up on google and they say "Dryer sheets are coated with positively charged substances that rub off on the clothes in the dryer in the presence of heat. With the clothes positively charged, there is no static cling." I'm still not sure if they work because they are charged, or because they are made of thin webbing that would physically allow for more/less contact when pressured. The Instructable you link to is a great one, but the conductive paste is not stretchy, so it cracks when applied to stretchy fabrics, when these are stretched. This is why i have not been working with it so much, but for non-stretch, it should be fine. Have you got any photos of your fabric pressure sensor?? Thanks!

[Graceria]

Hi. I can't remember if I asked this already, but is there any way to make these pressure sensors handle 4amps? I want to use these to trigger servos involved in the construction of animatronic wearable wings, but I'm told they won't handle 4amps.