Step 1: Prepare the Core Components

Component 1: A felted wool ball. This can be made using unwoven wool (I used Leicester wool), a felting needle, and a piece of foam. There are several tutorials specific to felting online. Here, we just have a basic ball.

Component 2: Two fabric swatches, each in an "+" shape. I used a thin muslin here.

Step 2: Add Conductive Thread to First Swatch

On one of the two swatches, sew a trace of conductive thread. I used stainless steel thread, and a couch stitch. Leave a few inches of extra thread at one end.

Step 3: Attach First Conductive Layer to Ball

Sew this first swatch onto the ball, with the conductive thread facing outward.

Step 4: Add the Second Conductive Layer

On the second swatch, create a new trace of conductive thread. This trace should be different than the first.

Not pictured here, but very important: cut a layer of velostat in the same "+" shape as the two conductive swatches. The velostat is a pressure-sensitive conductive sheet, and is essential to this sensor functioning.

You are going to wrap the second "+" swatch around the first one-- so that the conductive thread on each face each other. But! before attaching, make sure the velostat is sandwiched between the two.

Step 5:

Add a new, thin layer of wool around the sensor, and test the sensor before continuing.

If you are using Arduino, you can test the sensor using Arduino's analogRead(), for example in http://www.arduino.cc/en/Tutorial/AnalogInput. Open the console and make sure the values change as you expect when squeezing the ball.

Step 6: Have Fun With Shape and Color

This step is purely for aesthetics. I chose to add a bit more shape and color-- all using wool and felting needles.

Step 7: Play!

Hook your new pressure sensor up to some code, and play! As a deme, I use Processing and Arduino here so that my computer plays a sound effect when I squeeze the sensor hard enough.

Introduction: Needle-Felted Pressure Sensor