Previous Instructable >> Fabric Bend Sensor
Using neoprene, Velostat, conductive thread and stretch conductive fabric to sew your own fabric bend sensor. The sensor actually reacts (decreases in resistance) to pressure, not specifically to bend. But because it is sandwiched between two layers of neoprene, pressure is exerted while bending. Allowing one to measure bend (angle) via pressure.
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.
To prove the competitiveness of this sensor vs. a commercial bend sensor I made a short video in which Sheep demonstrates their similarities.
Step 1: Materials and Tools
Velostat is the brand name for the plastic bags in which sensitive electronic components are packaged. Also called anti-static, ex-static, carbon based plastic& (So you can also cut up one of these black plastic bags. But caution! Not all of them work!)
- Neoprene 1.5 mm thick HS quality from www.sedochemicals.com
- Velostat by 3M from http://www.lessemf.com/plastic.html
- Conductive thread from http://www.lessemf.com/fabric.html
- Stretch conductive fabric from http://www.lessemf.com/fabric.html
- Fusible interfacing from local fabric store
- Regular sewing thread from local fabric store
- Pen and paper
- Fabric scissors
- Sewing needle
- Possibly pliers for pulling needle through neoprene
Step 2: Stencil
Download Stencil PDF >> http://kobakant.at/downloads/stencils/neoprene-BS-improved.pdf
Step 3: Ironing
Now place the two pieces on top of the neoprene cutouts and fuse these together with an iron.
Step 4: Sewing
The reason the stitching on both sides must be identical is so that when they lie on top of each other (facing each other) the stitches crisscross and overlap in one point. This has the advantage that the stitches will be sure to cross (make contact at these points) and second that the point of contact is as small as possible. Ive found that if the conductive surfaces are too big that the sensitivity of the sensor is no longer good for what I want.
Step 5: Closing the Sensor
You can add more or less pieces of Velostat to control the sensitivity of the sensor.
Step 6: Sheep's Demo
You can also hook it up to your computer and graph the input. For this you will need to follow the instructions in the previous Fabric Bend Sensor Instructable (see step 7) >>
Let me know if you make one, I'd love to see some photos.