Introduction: Sew a Soft Circuit Touch Sensor

About: SENSOREE Design Lab crafts bio-responsive fashions with expressive technology. Our Therapeutic Biomedia monitors the body systems and animates emotion with audio, visual, or tactile displays. We work with futu…

Let us sew a circuit that responds to touch.


This tutorial shows how to make a Soft Circuit Touch Sensor.

The sensor is like a button. When pressure is applied to the sensor an LED lights up due to the variable touch pressure.


level: beginner. You will need basic sewing skills, and will learn basic electronic circuit.



MATERIALS


fabric base. new, used, or fused recycled plastic fabric from our technique on Instructables !

conductive fabric. we used copper taffeta from Less EMF Could also be copper or aluminum tape.

conductive thread. Less EMF

foam. recycled from packing materials

embroidery thread. Thread Art

3v coin cell battery. DigiKey

battery holder. Digikey

LEDs. Super Bright LEDs


TOOLS

sewing needle

needle nose pliers

scissors

and

a finger to press the sensor !

Step 1: Basic Circuit Pattern

Here is a sketch of a basic circuit [left] and the sketch of the pattern we will make [right].


The touch sensor will be the "switch" of our circuit. When you touch it, the LED will turn on.


Let us begin !

Step 2: DESIGN ! CUT Conductive Material for the Sensor

Cut two conductive fabric (we used copper taffeta) squares with tails.


The large square will be used for the sensor. The small square "tail" is to sew the conductive thread onto.


Cut one foam barrier larger than the conductive fabric.

The foam is the barrier of the sensor and regulates the touch sensor button.

Cut holes out of it about the size of your finger tip.



Step 3: SANDWICH the Materials and Sew Together

The sensor is like a foam sandwich.

The conductive fabric is like two pieces of bread with the foam in the middle. The foam prevents the two conductive surfaces from connecting until they get pressure.

SANDWICH fabric top / conductive material / foam with holes / conductive material / fabric base you are sewing this onto

Make sure the tails never touch! To affix the sandwich together, sew with embroidery or sewing thread, or fuse the plastic if you are using the plastic technique.


  • Do NOT use conductive thread for this step.
  • Make sure the tails do not touch.



Step 4: COMPLETE the Sensor

Stitch or fuse the sensor together.

Here is the completed sensor. Note the two tails do not touch.

Also, here is a basic sewing sketch. In case you have never sewn before, it will give you an idea.

Step 5: PREP the LED

Twist the tails of the LEDs

Using needle-nose wire pliers, clamp the LED tail and twirl around the nose. Do both sides. This will made it easier to sew.

One LED leg is negative and the other is positive. You can check which is which by placing on either side of a coin cell battery.

! WARNING ! The positive and negative tails must never touch on the circuit! or it wont work...

Step 6: SOLDER and Twist the Battery Holder Tails

This battery holder needs tails too.


Solder on copper wire and twist the tails like the LEDs. The tails give a surface to sew onto. Now it can be easily sewn onto the circuit.

Step 7: SEW the Circuit

Use a single strand of conductive thread and sew direct lines.


Secure all component connections by over-stitching at least 5 times to make good connections.


The circuit

  • + positive to positive
  • - negative to negative


Keep the positive and negative separate. Do not overlap conductive thread. They should never touch !


Circuit flow


+++Stitch one sensor tail to the positive LED tail and the other sensor tail to the positive end of the battery / power.


How it works: Pressing the sensor will connect the positive line and complete the circuit.


--Stitch the negative LED tail to the negative end of the battery.


[if you are a visual person, see the pattern sketch right.]

Step 8: TEST the Circuit

Now that you have sewn the circuit, test it.


Press the sensor, the LED should light up.

If it does not, check the connections. All the connections must be secure. Make sure the positive and negatives are in line.


Step 9: Diffuse LEDs

LEDs are bright and it is best to cover electronics for durability and also for style.

Cut a fabric piece to cover the LED and stitch in place.

You now have a finished design. Press away!