Conductive Fabric Pressure Sensor

Intro: 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)

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)

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

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!

Comments

[Astro01]

Nice project, I will try this! One question though, is it possible to have the data imaged with a software, to see the distributed pressure that is?
Cheers!

[angelisia]

hello
i am working on human posture detection using conductive stretchable fabric but i am not getting which fabric i should use. currently i am using eoentyx stretchable fabric which consist of spandex and knit jersey conductive also which constitute silver yarn with cotton but it is not showing much variation in resistance so please suggest me which fabric to be used. I read papers which tell PPY coated fabrics are good for stretchaable so i need your suggestion on it.

[SachinMY]

How are the results taken from the output that we get. Do we like need to have a setup to be done to validate the results ?

[Turtle Guy]

I would like to create a large pad with multiple sensors, that indicate when a person is lying on a bed. The multiple contact points would indicate if they are just sitting versus lying down. Wondering if a sheet of this material can have more than one sensor embedded in it, or do I need to use multiple pieces of material?

[NelsonN2]

[NelsonN2]

any way to make this waterprooff???thanks you guys

[joseph.m.jessup]

There are links to vendor sites, but no links to the actual products used. On the lessemf.com site, the term "stretch conductive fabric" is not even found. Can you be a little more specific regarding the fabric or part numbers? Thanks

[joseph.m.jessup]

There are links to vendor sites, but no links to the actual products used. On the lessemf.com site, the term "stretch conductive fabric" is not even found.

[jwakama]

Hi guys wanted to ask, what is the principle behind this sensor working. Maybe ohms law being applied? just curious. Thanks

[eklypz]

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!

[richddt]

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.

[billlavin]

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: [e-mail] Thanks so much...

[lnorooz]

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?

[mrmerino]

Could I rotate the connectors so they're closer to each other?

[Plusea]

yes, sure! just make sure the conductive opposite sides of conductive fabric never touch each other directly. only ever through the velostat.

[susanchen2011]

great job.

[freak88]

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 :).

[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!

[hazykev]

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

[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