Intro: 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.
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
needle nose pliers
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's begin !
Step 2: DESIGN ! CUT Conductive Material for the Sensor
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
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
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 ]
copper with tail
foam with holes cut in it [middle]
copper with opposite tail
Step 5: SANDWICH the Materials and Sew Together
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.
foam with holes
fabric base you are sewing this onto
make sure the tails do not touch !
Step 6: 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 7: 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 8: 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
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.
+++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
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 !