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The Edge | Colleen Morgan | Digital Visual Arts Catalyst

TimelineIntroduction to workshop materials

Take a look at some examples

Light Sensor

Temperature Sensor

Accelerometer

Other fun, useful links

Workshop Materials

conductive thread

lilypad light emitting diodes(LEDs)

Lilypad Pro Kit

Jumper Leads

Light Sensor

Temperature SensorAccelerometer

Examples

http://vimeo.com/20567677

Examples

http://www.youtube.com/watch?v=wgGWcFdDEws&feature=player_embedded

VJacket

Examples

http://www.youtube.com/watch?v=3q66T_x0Z7c

Electric Dress in Snow - Accelerometer and LEDs

Examples

http://www.youtube.com/watch?v=gaeYc0Iyt0k

LED Pants - Accelerometer and LEDs

Examples

http://www.youtube.com/watch?v=VG6NVdtaKKo&feature=related

Bono’s Laser Jacket

Examples

http://www.electricfoxy.com/zip/

Electricfoxy - ZIP

Control Your music with your zip

The Lilypad

An Arduino Micro Processor designed to be sewn.

Designed by Leah Buechley from MIT and SparkFun Electronics.

Can be programmed with the Arduino Software (Opensorce)

Is Washable!! (by hand)

The Lilypad

positive power supply(anode)

negative power supply

(cathode)

ResetButton

Digital I/O Pins1 - 13

Analog Input Pins

6 Pins For The FTDI Basic

Breakout Board

Arduino Software

Arduino is an opensource software

Free to download

Based on the C programming language and Processing Software

Runs on Windows, Mac OS and Linux

http://arduino.cc

Arduino Setup

1. Select Board: Lilypad Arduino w/ ATMega 328

2. Select Serial Port:

Mac will look something like this: /dev/tty.usbserial....

PC will look something like this: com1

http://arduino.cc

Tools Menu

Arduino Software

Text EditorFor Writing

Code

Toolbar

Debugging Text

Arduino ToolbarVerify/CompileChecks Code for Errors

Stop Open Sketch Upload

Serial MonitorSave SketchNew Sketch

Sketch Setup

sample code from arduino library

Light Sensor

Lilypad Light Sensor

20mm in Diameter

Light Sensor

The Lilypad Light Sensor uses an Analog Output value to sense Light. The sensor outputs values from 0 to 5V.

With exposure to bright light the sensor will output 5V. In total darkness the sensor will output 0V.

In normal indoor light contexts the sensor will output between 1 and 2V

Light Sensor

The Hardware Set Up

Analog Pin 0A0

Light SensorNow that we can see the values our sensor is spitting out we can start to use those values to control lights

We start off by defining some variables that we will use later on in our code.

Then in the setup procedure we begin the communication between the sensor and the computer. This is what the Serial.begin(9600) is all about. By doing this we are setting the Baud to 9600 which means we are communicating with the computer at a rate of 9600 bits per second.

In the loop procedure we then read the value the sensor is outputting and ask the computer to print it out for us so we can see it. We use the Serial.print function to get the computer to write the values for use to see.

Light SensorNow lets start on some code so that we can us the sensor values from the light sensor to control lights. First we need to define a couple of pins that we will attach LEDs to:

Now in our loop procedure we will write an if statement to get lights to switch on at different light values.

This if statement says: if the sensor value is less than 120 and greater than 70 then turn the LED attached to pin 13 on.

And it also has another possibility (the else if): if the sensor value is less than 50 and greater than 30 then turn the LEDs attached to pin 13 and 12 on.

Using these if and else if statements we are getting more lights to come on as it gets darker.

Light SensorWe can write the code in a slightly different way, so that it has the same effect on lights, but is easier to tweak depending on the type of light the garment will be in. We will start by defining some threshold values:

Now in our loop procedure we can change our if and else if statements to be based on the thresholds we have just defined.

Light SensorNow lets have a go at fading lights depending on light. We will write some code so that one LED fades in and one LED fades out as it gets darker. Lets take a look at the code:

Light SensorWe have a few interesting things going on in this code. Firstly we have a constraint so that we can determine the maximum and minimum readings of the light sensor depending on the light we are in at the moment.

Constraining the values to the maximum reading in the current light allows us to calibrate the light sensor to the current conditions in the room.

The next interesting thing is a map function. A map function allows us to re-map values from one range to another. The general form of a map function is:

map(value, fromLow, fromHigh, toLow, toHigh)

We are using a map function to convert the sensor readings to a value range between 0 and 255. We are doing this because we want to fade the LEDs so we need to make sure the values we are getting from the sensor can be ‘mapped’ within the Pulse With Modulation range of 0 - 255.

This is the map function we write to get the lights to fade out as it gets darker:

Light SensorTo get the lights to do the opposite, ie. to get the lights to fade in as it gets darker, we have to swap our toLow and toHigh values around. By doing this we are telling the computer that we want the lights to be at the brightest when the the light is as dark as it can get, and the lights to be at their dimmest when the light in the room is as bright as it can get.

Temperature Sensor

Lilypad Temperature Sensor (MCP9700)

20mm Diameter

Detects temps between -40C and +125C

Temperature Sensor

The Lilypad Temperature Sensor senses ambient temperature in a very simple and effective way.

The analog voltage it outputs is directly proportional to the temperature. (the analog voltage is independent of the power supply.)

We can use two very simple formulas to convert the voltage to temperature:

Voltage (in mV) = sensor reading * 3300.0/1024

Temp in °C = [voltage - 500] /10

Temperature Sensor

The Hardware Set Up

Analog Pin 0A0

Temperature SensorLets start by writing some code to read the values from our Temperature sensor:

This code allows us to print out the values from our sensor, both in raw analog values and in degrees celsius. We write float before our two formulas because we want to return values that are not necessarily whole numbers. Instead of writing ‘int’ which is short for integer or a whole number. We write ‘float’ to indicate that a number has a decimal point or is a floating point number. Floats can have up to 7 decimal points.

Temperature SensorNow that we can see what the temperature is we can write some code to get lights to come on at different temperature readings. Start by attaching two LEDs to the lilypad board and make sure you declare them as outputs in your setup procedure.

I have written some code so that a green light is on at the ambient temperature of the room and a red lights comes on when the temperature sensor is touched. With this code, your shirt could glow red when you get a hug from your friends!

As long as you are in a room that is cooler than 26 degrees that is!!

Remember you can tweak the code for different contexts.

Temperature SensorTo make our temperature readings a little more accurate we can do something called ‘Smoothing’. Smoothing is a technique of gathering a number or sample readings from the sensor and averaging it out to get an average reading. We will start by defining the variables we will need to do the smoothing.

int readings[sensorReadings]; is what we write to declare an array. An array is collection of variables that are accessed with an index number. We are using this array to store 5 readings from the temperature sensor.

We will then add each of the readings together an divide it by the number of readings in the index to get an average reading.

Temperature SensorHere is the code we need to write to make the smoothing happen:

Now our temperature readings and light changes will be a bit more accurate!!

Motion Sensor (Accelerometer)

Lilypad Accelerometer Sensor (ADXL335)

20mm Diameter

A three-axis accelerometer

Detects movement x, y and z axis.

Can be used to detect tilt and acceleration

The Hardware Set Up

Analog Pin 0

Analog Pin 1

Analog Pin 2

Motion Sensor (Accelerometer)

Motion Sensor (Accelerometer)We will start by writing some code to get readings from our accelerometer.

We have to declare some variables first and in our setup procedure we have to open the serial port to start communication between our sensor and the Lilypad and set our LED pins as outputs:

Motion Sensor (Accelerometer)In our loop procedure we can read each of our axes and send the values to the computer.

When you open your serial monitor you should see something a little like this:

When your sensor is flat you should get readings close to: X: 512, Y: 512, Z: 612

Motion Sensor (Accelerometer)Now that we can see the values we are getting from our accelerometer we can start to figure out how to write some code for lights to respond to the movement of the sensor.

The first sketch we are going to write will detect the tilt of the sensor on the x and y axis and fade LEDs accordingly. In order to write this code we need to figure out what values we get when we tilt the sensor. These are some approximate values that I came up with:

Tilt x-axis away = 370 (minimum value)Tilt x-axis towards = 630 (maximum value)

Tilt y-axis left = 370 (minimum value)Tilt y-axis right = 630 (maximum value)

Now we can use these values to write some code.

Motion Sensor (Accelerometer)The first thing we are going to do is write a function to constrain the sensor values we want to use:

To stay on the safe side I have made the maximum and minimum values inside the maximum and minimum values I identified earlier.

Now we want to map these constrained maximum and minimum values to the PWM range (between 0 and 255):

Now all we have to do is write those PWM values to our LEDs for each axis and add a delay that will give us a good balance between movement and glow:

Motion Sensor (Accelerometer)Now lets write a new sketch to detect the acceleration of the sensor on each of the three axes.

Acceleration is a measure of how fast the speed of something is changing.

Accelerometers provide an output voltage proportional to the linear acceleration in each axis. Zero acceleration (or zero-g offset) is usually defined as an output voltage equal to half the supply voltage. The Lilypad provides a supply of 3.3V, so this would be a zero-g offset equal to 1.65V or 1650mV. Voltages above 1.65V indicate a positive acceleration. Voltages below 1.65V indicate a negative acceleration.

The magnitude of the acceleration is typically expressed in units of g. 1g = the Earths gravitational acceleration (gravity). So when an accelerometer is still the z axis (up-down has a force of 1g.

Acceleration is caculated by finding the difference between the measured output and the zero-g offset then dividing by the sensitivity of the accelerometer (expressed in V/g or mV/g). The sensitivity of the ADXL355 accelerometer, the one we are using today is 300mV/g or 0.300V/g.

So acceleration can be calculated using the following two formulas:

voltage = (reading from pin)*3300 / 1024aaccelration = (voltage - 1650V) / (300V/g)

Motion Sensor (Accelerometer)Lets start on the code. We will start by writing the code to read the values for each axis, just like we did in the last sketch:

Motion Sensor (Accelerometer)Now it we need to introduce a couple of things in order to detect acceleration. We will use the formulas we identified earlier.

First up lets declare a couple of variables and define the Pins we will attach our LEDs to for each axis:

Motion Sensor (Accelerometer)Now for the code that puts the formulas into play. We will start with the x axis:

The first two lines print our the analog reading of the x axis.

The third line is our formula for calculating voltage from the analog reading of the x axis. The forth and fifth lines tells the computer to print out this information for us to see.

The sixth line is our formula for calculating acceleration from the voltage reading we just calculated. The seventh and eighth line tell the computer to print out this information for us to see.

Motion Sensor (Accelerometer)Now we can write this code again to calculate the acceleration on the y and z axes.

Motion Sensor (Accelerometer)Now that we can see the acceleration values or g force of each axis, we can write some if statements to get the LEDs to light up as the sensor detects movement on each of the axes. Here are the if, else if and else statements I wrote for the x and y axes:

Motion Sensor (Accelerometer)The statements I wrote for the z axis is slightly different. The g force of the z axis is different due to gravity.

Useful LinksHardware

LittleBird Electronics - littlebirdelectronics.com.au

Jaycar - jaycar.com.au

Sparkfun - sparkfun.com (america)

Inspiration

Fashioning Technology - fashioningtech.com

Diana Eng - fashionnerd.com

Talk2MyShirt - talktomyshirt.com

Useful LinksInnovative Artists to WatchHussein Chalayan - www.husseinchalayan.com

Electricfoxy - www.electricfoxy.com

Moon Berlin - www.moon-berlin.com

Other Fun...Materials

Pressure Sensors & Flex sensors

Speakers

Switches

Wireless Communication - Live data feeds

Workshop

Making Things Sense Workshop - 7th & 8th May

What Next...Making Things Sense Workshop - 7th & 8th May