Making a Flex Sensor

Making a flex sensor is cheaper than buying one. Although results can vary depending on how much or the size of materials used. The below method is what I used for making the bi-directional flex sensors used for the wearable gesture device. 

Velostat

Velostat is a pressure sensitive conductive material. Pressure sensitive meaning that bending, squeezing or applying pressure to this material will reduce its resistance value making it more conductive. So when used in our flex sensor, this changing value will allow us to determine bending such as arm, wrist and finger movements.

Conductive thread

This conductive thread can be used to sew conductive fabrics together. In this project it is used as the flexible conductive material needed for the contacts for each side of the resistor.


Conductive Fabric

This is used as tabs or contacts and placed on the end of each thread.

Bend sensor design

Material
Size (L x W)
Qty
Velostat (pressure sensitive)
11cm x 2cm
3
Conductive thread
10cm x 2.5cm
2
Conductive Fabric
1.5cm x 0.5cm
2
Adhesive Tape
12cm
2

Steps
  1. Place one piece of tape flat with the sticky side facing up.
  2. Place one piece of conductive thread across one side of the tape making sure not to go over the edge of the tape.
  3.  One piece of conductive fabric is then placed over the end of the thread with end sticking out the end of the tape.
  4. Place one piece of Velostat on top making sure to cover the thread.
  5. Repeat steps 1-4 using a second piece of tape, thread, conductive fabric & Velostat.
  6. Place the third piece of Velostat in between and sandwich both pieces together.  

Results

The bend sensor results were measured using a multimeter. The measurements were taken at three different positions: flat (no bend), 45 degree bend & 90 degree bend. 
  1. Resistance no bend 180 degrees:   approx 4.5 kohm
  2. Resistance bend at 45 degrees:      approx 3 kohm
  3. Resistance bend 90 degrees:          approx 2 kohm

The below video is a quick demonstration on how to build a bend sensor. This was the first video I found when searching for tutorials on making flex sensors.

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