05. E-textiles¶
Week 05: This week we got introduced into the world of electronics, wearables and microcontrollers! We used Arduino IDE to code the project and the Adafruit Flora as the microcontroller.
• • •
Introduction¶
Assignment
- Build at least one digital and one analogue soft sensor, using different materials and techniques.
- Document the sensor project as well as the readings got using the AnalogRead of Arduino
- Integrate the two soft sensors into one or two textile swatches using hard soft connections
- Document the circuit and its schematic
- Upload your arduino code as text
- Upload a small video of the swatches functioning
- Integrate the swatch into a project (extra credit)
Inspiration¶
Alumni:
- Anna Cain - similar idea to me of creating an LED necklace
The Wider World!
Cyborg, artist and dancer - she has inserted sensors into her feet to feel the earths vibrations and translate this feeling into a dance.
[1] Photo by Cyborg Arts on "Moon Ribas"
One step beyond this week! I want to maybe grow crystals like these on either whatever I produce this week or on some biomaterials I create in biofabrication week.
E-textile artist who has created a wearable haptic glove that controls musicians audio and visuals, and e-textile stretch circuits ( a "stretchy human breadboard"!?)
[2] Photo by Rachel Freire on "Second Skin"
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Tools¶
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TinkerCAD - for drawing out circuit schematics and 3D diagrams
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Fab Labs Docs - for info on setting up Arduino and Flora
Electronics Basics¶
Key Words
Voltage: The electrical potential difference between two points - measured in Volts (V)
Current: The rate of flow of charge - meausred in Amps (A)
Resistance: The opposition to the flow of electric current in a material or circuit - measured in Ohms (Ω)
Series Circuit : All components are connected end to end to form a single path in the circuit. Voltage is shared between each component, the current is the same in each component.
Parallel Circuit : An electrical path that branches so that the current is divided between each path. The voltage in each component is the same.
Short Circuit : A low resistance path for the current to follow. This results in excessive current flowing through the circuit.
Some basic electronics laws:
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Voltage = Current x Resistance
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Electricity runs from the positive terminal to the negative terminal.
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Electrical energy follows the path of least resistance to the ground.
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Resistance increases with distance, no matter the material.
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Increasing the surface area for electricity to flow decreases the resistance.
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If there's 0Ω in a circuit then there is infinite current which causes a short circuit
Building a circuit¶
This exercise was just a refresher for me and it actually felt fun doing it again since uni. We made a simple series circuit with a 9V battery, LED and 150kΩ resistor.
I used TinkerCAD to draw schematics and 2D models of the circuits.
Here is a simple parallel circuit hooked up to a power supply of 3.3V. I learnt that RGB LEDS all have different forward voltages depending on their colour - this means that they each shine with a different intensity. Warmer colours ( i.e. red) have a lower forward voltage so shine brighter than cooler coloured LEDS ( i.e. blue) which have a lower forward voltage. This meant that on our circuit each LED had a different brightness.
Designing a Digital Sensor Prototype¶
A digital sensor is one that only reads 0/1 or ON/OFF. I wanted to make one that was similar to a necklace clasp so that when the clasp was closed the circuit was running.
All you need is: - yarn threads
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conductive thread
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conductive tape
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normal tape
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multimeter
I plaited some conductive thread through 2 pieces of yarn and taped the end with electrical tape, I taped the other end with normal tape just to keep the threads together.
With Citlali's help we tested the connections to check for continuity. The ends with normal tape were pressed to the multimeter (on the soundwave/continuity setting) while with our other hands we touched the two electrically taped ends together and heard a beeeeep so that's all good!
Designing an Analog Sensor Prototype¶
An analog sensor is one that has variable readings and for this we needed resistance - Velostat! I wanted to use the wool to create some sort of stress ball that can measure the pressure from your clench.
All you need is: - velostat
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sewing needle and thread
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conductive thread
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conductive tape
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multimeter
I cut some pieces of velostat and sewed them using normal thread to the centre of the wool. On the other side I scrunched up bits of wool and wound the conductive thread around them to make a tight ball which I placed behind the velostat - make sure that none is visible on the other side as if the two separate conductive thread pieces touch this creates a short circuit. Leave the ends of the yarn hanging out of the wool and tape them with electrical tape to make them easier to clip with alligator clips to the circuit.
Using the multimeter again we pressed the ends of the cables to the velostat and pressed down on the wool. The max resistance was ~20kΩ and the min was ~5kΩ - so I needed to choose a resistor for the next step at around the 10kΩ mark.
Adafruit Flora and Arduino¶
The Flora is a microcontroller board for wearable projects with many built-in features which you can upload to your designs through Arduino. You can cehck out the libraru of designs other people have made here :)
The important pins to note are:
- Ground
- Pin D12 (Digital) / A11 (Analog)
- Voltage 3.3V
Code Example¶
Here is the basic starter Arduino code to allow the Adafruit Flora to read the button sensor (Digital) and pressure sensor (Analog).
Remember:
- Analog sensor is connected to PIN 11
- Digital sensor is connected to PIN 12
int value;
// the setup function runs once when you press reset or power the board
void setup() {
pinMode(11, INPUT); // Analog Pin 11/ Digital Pin 12 is connected to my sensor. Use INPUT for Analog sensor and INPUT_PULLUP for digital sensor so that flora uses the internal resistance of the microcontroller.
Serial.begin(9600); // makes a communication between the computer and flora
}
// put your main code here, to run repeatedly:
void loop() {
analogRead(11); // function to read our sensor which is connected to pin 11 for analog and pin 12 for digital. digitalRead() for digital sensor.
value=analogRead(11); // value is going to continuously be reading whatever analogRead(11) is receiving.
Serial.println(value); // prints the value
delay(100); // gives a pause between each reading
}
• • •
Below are the values that the Flora records when the conductive ends are touched together on the Digital Necklace Clasp Sensor - notice how it is only 0/1 values.
Here are the values for when the Stress Ball Analog Pressure Sensor is pushed down. The values range from 0 - 400+ .