Stitching conductive thread into neoprene to create a pressure sensitive pad. This sensor is very similar to the Fabric Bend Sensor or vis-versa. And also close to the Fabric Pressure Sensor, but the difference is that the conductive surface is minimized by stitching only a few stitches on either side with conductive thread. This creates a good fingertip pressure range.
The resistance range of these pressure sensors depends a lot on the initial pressure. Ideally you have above 2M ohm resistance between both contacts when the sensor is lying flat. But this can vary, depending on how the sensor is sewn and how big the overlap of the adjacent conductive surfaces are. This is why i choose to sew the contacts as diagonal stitches of conductive thread - to minimize the overlap of conductive surface. But only the slightest touch of the finger will generally bring the resistance down to a few Kilo ohm and, when fully pressured, it goes down to about 200 ohm. The sensor still detects a difference, right down to about as hard as you can press with your fingers. The range is non-linear and gets smaller as the resistance decreases.
I am also selling these handmade Thread Pressure Sensors via Etsy. Although it is much cheaper to make your own, purchasing one will help me support my prototyping and development costs >>
http://www.etsy.com/shop.php?user_id=5178109
As in all my Instructables 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. But they also ship to Europe within about 10 days.
Velostat is the brand name for the plastic bags in which sensitive electronic components come packaged in. Also called anti-static, ex-static, carbon infused 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, so test them first!)
To make the sensor fully fabric one can use EeonTex conductive textile (www.eeonyx.com) instead of the plastic Velostat. Eeonyx normally only manufacture and sells its coated fabrics in minimum amounts of 100yds, but 7x10 inch (17.8x25.4 cm) samples are available free of charge and larger samples of 1 to 5 yards for a minimum fee per yard.
The resistance range of these pressure sensors depends a lot on the initial pressure. Ideally you have above 2M ohm resistance between both contacts when the sensor is lying flat. But this can vary, depending on how the sensor is sewn and how big the overlap of the adjacent conductive surfaces are. This is why i choose to sew the contacts as diagonal stitches of conductive thread - to minimize the overlap of conductive surface. But only the slightest touch of the finger will generally bring the resistance down to a few Kilo ohm and, when fully pressured, it goes down to about 200 ohm. The sensor still detects a difference, right down to about as hard as you can press with your fingers. The range is non-linear and gets smaller as the resistance decreases.
I am also selling these handmade Thread Pressure Sensors via Etsy. Although it is much cheaper to make your own, purchasing one will help me support my prototyping and development costs >>
http://www.etsy.com/shop.php?user_id=5178109
As in all my Instructables 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. But they also ship to Europe within about 10 days.
Velostat is the brand name for the plastic bags in which sensitive electronic components come packaged in. Also called anti-static, ex-static, carbon infused 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, so test them first!)
To make the sensor fully fabric one can use EeonTex conductive textile (www.eeonyx.com) instead of the plastic Velostat. Eeonyx normally only manufacture and sells its coated fabrics in minimum amounts of 100yds, but 7x10 inch (17.8x25.4 cm) samples are available free of charge and larger samples of 1 to 5 yards for a minimum fee per yard.
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Signing UpStep 1: Materials and tool
MATERIALS:
- 1.5 mm neoprene from http://www.sedochemicals.de
- Conductive thread from www.sparkfun.com
also see http://cnmat.berkeley.edu/resource/conductive_thread
- Stretch conductive fabric from www.lessemf.com
also see http://cnmat.berkeley.edu/resource/stretch_conductive_fabric
- Fusible interfacing from local fabric store or
also see http://www.shoppellon.com
- Velostat by 3M from http://www.lessemf.com
also see http://cnmat.berkeley.edu/resource/velostat_resistive_plastic
- Regular thread
- Machine poppers/snaps
TOOLS:
- Pen and paper
- Fabric scissors
- Iron
- Sewing needle
- Popper/snap machine (handheld or hammer and simple version)
- 1.5 mm neoprene from http://www.sedochemicals.de
- Conductive thread from www.sparkfun.com
also see http://cnmat.berkeley.edu/resource/conductive_thread
- Stretch conductive fabric from www.lessemf.com
also see http://cnmat.berkeley.edu/resource/stretch_conductive_fabric
- Fusible interfacing from local fabric store or
also see http://www.shoppellon.com
- Velostat by 3M from http://www.lessemf.com
also see http://cnmat.berkeley.edu/resource/velostat_resistive_plastic
- Regular thread
- Machine poppers/snaps
TOOLS:
- Pen and paper
- Fabric scissors
- Iron
- Sewing needle
- Popper/snap machine (handheld or hammer and simple version)
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Interesting post, but I was wondering, can this sensor be used to light a set of LED's?
Thanks in advance.
Can I ask what program you are using on your computer in the video?
Is that possible to measure big load in this system?
Thanks
I was wondering if you were going to create a number of smallish, closely spaced sensor buttons that are arduino interfaced, would you recommend using the conductive thread method as per here, or the conductive fabric sensor as in your other instructable? which would be more flexible and which more durable?
Really cool instructable.
i want to ask about how to make a pressure sensor to stop an alarm
My idea is to make a carpet with an alarm ( it's really hard to wake up everyday at 5:00 am to go to college) and this alarm will not stop unless i'm standing on this carpet
hope that someone can help me through this quickly :)
lessemf.com
mutr.co.uk
plugandwear.com
>> http://www.instructables.com/id/SZED352FC2EFZ6V/
not sure it the thread is strong enough for trip wire. it does not rip to easily but it does. you can get stronger conductive thread from lame life saver in canada:
>> http://members.shaw.ca/ubik/thread/
or in the uk from mutr:
>> http://mutr.co.uk/
what are you devising?
the best solution is always to just try it out.
Can I talk to you on the phone
would it be necessary to make multiple 'contact points?'
if so, can i connect all the positives to one wire and negatives to another safely?
i really appreciate all of you help :)
>> http://www.kobakant.at/DIY/?p=48
right now i have no ideas of how to make it into a NC switch though.....
LS is super soft and HHS is much tougher and less "squishy" but still quite soft. S and HS are in between. NF i have never tried and W just means that is their white neoprene.
for my sensors i have been working with S and HS mainly. but LS and HHS would work too. hope this helps.
I made the little sensor and then a second "jacket" to put over it to cover the exposed thread (fleece isn't thick enough to thread inside). And so you couldn't see the two tabs separately.
Thanks for posting this instructable!
I'm kind of interested in getting the different animals to create drawings in processing (so pressing the bunny draws different sized bunnies depending on how hard you're pressing). But I'm pretty new at all this and still have to learn how to get processing to even read from the arduino.
Another idea I want to try out is making a pressure sensitive yoga mat. I'm not sure what it would control, maybe some lights or drawing or music. I just think it would be fun to use yoga/pilates to make stuff. I'd love to hear any tips/ideas you might have for it.
I actually made a pair of slippers with these pressure sensors embedded and then wrote a little drawing application. reading the analog input from the arduino into processing is super simple and leads to lots of ideas. here is the JoySlippers Instructable and in step 6 there are links to downloading the arduino and processing code that i used for my simple drawing application.
When i showed the JoySlippers at the maker fair last april, a lot of people said that it would be a great idea for visualizing yoga moves.... but i don't do yoga myself, so i never picked up on it and i'm definitely interested to see what you can make out of it!
i'm also interested in sound output, because visuals always require you to look at something. though i'm more of a visual person myself and have never really worked with sound before....
keep me updated:-)
and they're all featured....
*jealoussyyyy*
but since this has been featured, more people will know about it!
i'm currently working on a coil gun, and will post an ible... this could take a while...