How to make a flexible fabric pressure sensor from 3 layers of conductive fabric.

This Instructable is somewhat outdated. Please view the following Instructables for improved versions:
>> https://www.instructables.com/id/Conductive-Thread-Pressure-Sensor/
>> https://www.instructables.com/id/Flexible-Fabric-Pressure-Sensor/
>> https://www.instructables.com/id/Pressure-Sensor-Matrix/
>> https://www.instructables.com/id/Stickytape-Sensors/

Step 1: Materials

You will need:
(The amounts of material depend on how large you want the touch pad to be)
- Ex-static fabric from www.lessemf.com
(also see http://cnmat.berkeley.edu/resource/ex_static_conductive_fabric)
- Stretch conductive fabric from www.lessemf.com
(also see http://cnmat.berkeley.edu/resource/stretch_conductive_fabric)
- Cotton thread or a kind of non-conductive adhesive

Optional:
- Another material as padding on either side. In the example I'm using Neoprene (ordered from Sedochemicals)
- An LED to show it works
- Energy source. In the example I'm using 3x1.5 Volt batteries
- Cables to connect

Step 2: Layering

Layer you materials as follows:

TOP
(- Optional layer or neoprene)
- Stretch conductive fabric*
- Ex-Static conductive fabric*
- Stretch conductive fabric*
(- Optional layer or neoprene)
BOTTOM

*VERY IMPORTANT:
Layer the Stretch and the Ex-Static conductive fabric so that the layers of Stretch DO NOT touch!
The layers of Stretch conductive fabric should be displaced from one another in opposite corners (so that later they can both be sewn into place without the thread ever passing through both Stretch conductive layers at one time) and sticking out slightly at opposite ends (so that later on they can be connected to a power source and electric components).

Step 3: Sewing

Now that the layers are in place, carefully sew around the edges making sure never to stitch though both Stretch conductive layers at the same time.

This step can be tricky and you can use either a sewing machine or sew it by hand as in the example.

Step 4: Setup

This setup demonstrates how that applying pressure to the touch pad changes the brightness of the LED.

- Connect one of the (sticking out) Stretch conductive layers to the + pole of your energy source (4.5 Volt)
- Connect the + pole of the LED to the other (sticking out) Stretch conductive layer
- Connect the - pole of the LED to the - pole of your energy source
- Apply pressure to the touch pad

The amount of current changes depending on the amount of pressure to one point and the area of pressure.