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Picture of Sew a Soft Circuit Touch Sensor
Let us sew a circuit that responds to touch.

This tutorial shows how to make a Soft Circuit Touch Sensor.
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. copper taffeta from Less EMF

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 or Radio Shack is good for local pick up in the US


TOOLS

sewing needle

needle nose pliers


scissors

and

a finger to press the sensor !

 
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Step 1: Basic Circuit pattern

Picture of 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's begin !

Step 2: DESIGN ! CUT conductive material for the sensor

Picture of DESIGN !  CUT conductive material for the sensor
touchsensor0.jpg
Circuits like to connect, but sometimes need help...

Cut two conductive copper taffeta squares with tails.
The large square here will be used for the sensor.
The small square "tail" is to sew the conductive thread onto.




Step 3: CUT foam

Picture of CUT foam
The foam regulates the touch sensor button.

This is the barrier of the sensor.

Cut it larger than the conductive fabric.

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

Step 4: LAYOUT the sensor

Picture of LAYOUT the sensor
The sensor is like a foam sandwich.

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

Make sure the tails never touch !

[ from left to right ]
sensor top
copper with tail
foam with holes cut in it [middle]
copper with opposite tail
sensor bottom

Step 5: SANDWICH the materials and sew together

Picture of SANDWICH the materials and sew together
touchsensor23.jpg
touchsensor24.jpg
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.

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

make sure the tails do not touch !

Step 6: COMPLETE the sensor

Picture of COMPLETE the sensor
sewing.jpg
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 7: PREP the LED

Picture of PREP the LED
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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 8: SOLDER and twist the battery holder tails

Picture of SOLDER and twist the battery holder tails
This battery holder needs tails too.

Solder on copper wire and twist the tails like the LEDs.
Now it can be easily sewn onto the circuit.


Step 9: SEW the circuit

Picture of SEW the circuit
touchsensor3.jpg
touchsensor20.jpg
touchsensor10.jpg
conductivo.jpg
Use a single strand of conductive thread and sew direct lines.

Secure all component connections by over-stitching at least 5 times. Make good connections!

A circuit must run it's course...
+ positive to positive
- negative to negative

Keep the positive and negative separate. They should never touch !
! very importante ! no overlapping.

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 10: TEST the circuit

Picture of TEST the circuit
touchsensor06.jpg
touchsensor13.jpg
touchsensor01.jpg
touchsensor09.jpg
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.

Now, don't go blind! LEDs are bright. To protect your eyes and everyone else, cut a fabric piece to cover the LED and stitch in place.

Press away !