Physical Computing Tutorials

Transcription

1 Physical Computing Tutorials How to install libraries Powering an Arduino Using an MPR121 capacitive touch sensor Using a Sparkfun MP3 Trigger Controlling an actuator with TinkerKit Mosfet Making sounds with a piezo Using a Sparkfun Sound Detector How to connect a push button or switch Using a HC-SR04 distance sensor Connecting a Potentiometer How to connect a Light Dependent Resistor (LDR) How to use a rotary encoder

2 How to install libraries Arduino libraries are collections of code that are designed to provide additional, reusable functionality or to simplify using external electronic modules. Libraries typically come with examples of how to use them. The library developer usually provides online documentation and explains how it possibly relates to what you are trying to achieve. Installing a library There are three different ways to install libraries; we'll show you each of them. Arduino Library Manager The simplest method of installing libraries is using the Library Manager built into the Arduino IDE. You can access the Library Manager from the menu bar:

3 A new window will open: From here you can search for libraries to use in your code. Only a few libraries are

4 currently available this way, as this feature is relatively new. You will often have to manually download and install a library, following the other two processes. ZIP library Locate and download a library you wish to use. Sometimes the library will download as a *.zip archive, which can sometimes be installed directly without restarting the Arduino IDE. Similar to the Library Manager, this option is in the menu bar: Use the file dialog to locate and select the zip file from your Downloads folder. You will be notified if the installation has been successful otherwise you'll need to install manually. Manually adding libraries This is the original method of adding libraries. 1. Locate the Arduino folder inside your Documents directory. 2. Open the libraries folder. If not found, create a new folder with that name (must be lowercase). 3. Unzip the library archive that you wish to install. 4. Inside the archive you should find a folder bearing the name of the library for

5 example 'MPR121'. 5. Copy this entire folder (named 'MPR121' in our example) into the Arduino's libraries folder. 6. Restart the Arduino IDE. 7. In the menu bar, select Sketch > Include Library. You should now see that your library is listed:

6 Powering an Arduino Here is some resources about powering Arduino or other electronic projects: General How to power an Arduino: How to power a project: What adapter? Portable / Battery powered For portable projects some info on battery usage

7 9V batteries are bad: Motors (To do)

8 Using an MPR121 capacitive touch sensor What is the MPR121? The MPR121 is a tiny microchip formerly manufactured by NXP, now under Resurgent Semiconductor, it is a tiny surface mount device that provides 12 capacitive touch electrodes through an I2C interface. What is capacitive touch? Capacitive touch the the technology used on modern touch sensitive devices such as phone and tablet screens, trackpads and computer mice like Apple's Magic Mouse. Capacitive touch takes advantage of the human body being electrically conductive, this is why using a pen on a smart phone doesn't work and styluses for these devices are made of metal so they will make an electrical connection.

9 Capacitive touch is relatively complex to understand but fundamentally the sensor can detect when you are in proximity or actually touching the electrode, or any conductive part between the chip and the end of the wire. If you extend a wire from the electrode, even if it is shielded with plastic, it will probably detect you touching the wire just the same as the exposed metal part. Different versions of MPR121 The first common use of the MPR121 in physical computing was the now discontinued Sparkfun MPR121 breakout, this is the most commonly available version in the Prototyping Lab here at LCC. MPR121 breakouts from Adafruit and Seedstudio also exist, and we've begin replacing our Sparkfun boards with Adafruit as the Sparkfun boards break and need replacing. Additionally the MPR121 is used in the Bare Conductive Touch Board which is effectively an Arduino Leonardo with an MPR121 and MP3/WAV/OGG/MIDI player (similar to the Sparkfun MP3 Trigger) integrated one board. Key differences

10 Sparkfun MPR121 Power input: 3.3V only! 5V is the primary reason these break. Address: 0x5A is the default address, changing this requires alterations to the board Adafruit MPR121 Power input: 3.3V to 5V Address: 0x5A, it is also relatively easy to configure the address to 0x5B, 0x5C or 0x5D allowing up to 48 electrodes (12 x 4). Wiring Wiring is pretty simple, it's an I2C component so it's relatively standard. Warning The Sparkfun MPR121 is a 3.3V device, do not connect the power pins to 5V, you will instantly destroy the board.? Older Arduino boards Some older Arduino boards do not have SDA and SCL pins as shown in the diagrams,? in this case you'll need to look it up on the boards documentation, however most Arduino boards used A4 as SDA and A4 as SCL.

11 Sparkfun MPR121 Adafruit MPR121

12 Library Adafruit, Sparkfun, Seeedstudio and Bare Conductive all provide Arduino libraries, however by far the best which includes tools for visualising the data is the Bare Conductive Touch Board library and grapher. All libraries should all work interchangeably as long as you get the correct address and IRQ pin.

13 The key thing to remember when using examples from the Bare Conductive library is that they use the address 0x5C rather than the default 0x5A address used on both the Sparkfun and Adafruit boards, also ensure that you use the correct IRQ pin based on the example you are using. We have a tutorial on how to install a library here. Getting started After installing the library and wiring the board, go ahead and use the examples in the File > Examples menu in Arduino, the Simple Touch example is particularly good as it's simple to check it's working. Basic Example This is a basic example of using the MPR121 with the Bare Conductive MPR121 library to get the proximity value and touch status, this can easily be extrapolated into a project. Sketch: Basic Example CSV Example This is an example using the MPR121 with the Bare Conductive MPR121 library to output each electrode's touch status to the serial port as a comma separated string. This example can be modified to work with MaxMSP easily by changing the delimiter line

14 to a space instead of a comma: #define DELIMITER " " You could also modify this example to output the proximity data, instead of the touch data by modifying the updatetouchdata line to: MPR121.updateFilteredData(); And the gettouchdata line to: Serial.print( MPR121.getFilteredData( i ) ); Sketch: CSV Example

15 Using a Sparkfun MP3 Trigger What is the MP3 Trigger? The MP3 trigger is a board made by Sparkfun electronics that provides a way to play MP3 files from a Micro SD card via either one of 18 TRIG inputs on the board, or serial communication with the board. The MP3 Trigger has a headphone output which can be connected to powered speakers of your headphones for testing. Loading files You must us a micro SDSC (up to 2GB) card, or a SDHC (up to 32GB) card formatted in FAT16 or FAT32. After inserting the card you must power cycle the MP3 Trigger so it detects the card, this can be done by switching the USB <-> EXT switch back and forth.

16 USB: means power from the Arduino. EXT: means power via the 2.1mm connector to the left of the switch. File naming Files should be named 001.MP3 through 018.MP3, and the MP3 Trigger will match the file name to the TRIG pins, if you controlling the MP3 Trigger via serial the number will match 0 to 255. Wiring Wiring is simple: There are three wires: 1. Ground (GND connects to GND) 2. Power (USBVCC connects to 5V) 3. Data (RX on the MP3 Trigger to TX on the Arduino) 4. Optionally you can connect the TX on the MP3 Trigger back to the RX on the Arduino if you wish to get playback status information.

17 Warning Arduino Leonardo, unlike Arduino Uno has two serial ports. In this example we will be using Arduino Uno, if however you want to use Arduino Leonardo you'll need to use Serial1 which is the RX/TX pins on pins 0 and 1, rather than Serial which is the USB serial monitor. Read more? Getting started There are libraries available for the Sparkfun MP3 Trigger however it's so easy to use it's easier to use Serial.print to control it rather than a library.

18 Basic Example This basic example will play 001.MP3-005.MP3 from the SD card with a 1 second delay between playing each. This is a great demo of how to play files from the SD card via Serial. Sketch: Basic example - Arduino Uno Sketch: Basic example - Arduino Leonardo Sample MP3 files To help you get up and running quickly there are 5 example MP3's you can use with the basic example of Tom saying 1-5. Example MP3 Files Resources Sparkfun Hookup Guide

19 Controlling an actuator with TinkerKit Mosfet What is the TinkerKit Mosfet? The TinkerKit Mosfet is a simple module for controlling devices like motors, solenoids, LED strips and electromagnets which require higher voltages and currents than the Arduino can handle alone. Typically you might find an example of a mosfet circuit online when trying to solve this problem, however high current circuits can melt breadboards, and accidentally wiring up the 12 or 24 volt power supply to your Arduino is a easily made mistake that will damage the Arduino and potentially your computer.

20 For this reason we use a small, cheap module which takes away all these headaches, on the Arduino side you have three header pins and on the actuator side you've got your power in, and switched power out. In effect TinkerKit Mosfet is an electronic switch that can turn your actuator on and off using an Arduino. Wiring There are three wires to connect on the Arduino side: 1. Ground ( - connects to GND ) 2. Power ( + connects to 5V) 3. Signal (The middle pin connects to your Arduino pin e.g. pin 6) On the other side there are four screw terminals, labeled: GND (Connects to your power supply ground) +V (Connects to your power supply positive) M+ (Connects to one side of your actuator) M- (Connects to the other side of your actuator) Warning The TinkerKit Mosfet can only drive up to 24V DC.?

21 Getting started After wiring up the board it can be controlled via digitalwrite just like an LED. There are some quick examples below: Basic Example This basic example is effectively the blink sketch, the TinkerKit Mosfet operates just like any other digital device. #define actuatorpin 6 void setup() {

22 pinmode( actuatorpin, OUTPUT ); } void loop() { digitalwrite( actuatorpin, HIGH ); delay( 1000 ); digitalwrite( actuatorpin, LOW ); delay( 1000 ); } Advanced Example You can also control the speed of some actuators, normally this is only useful for motors, this is accomplished using analogwrite (PWM) this is effectively the same as setting the brightness of an LED. Danger Below a certain voltage/pwm value most actuators such as motors will stall (won't turn), this will cause the motor to become extremely hot potentially causing a fire damaging the motor, or burning you. Always make sure your code prevents the speed of the motor going below the stall speed, you can find the stall speed by testing different values until the motor is only just turning, this should be your minimum.? #define actuatorpin 6 void setup() { pinmode( actuatorpin, OUTPUT ); } void loop() { // This example uses 128 as an example of the minimum motor speed to protect the motor for ( int i = 128; i < 255; i++ ) { analogwrite( actuatorpin, i ); delay( 10 ); } }

23 Making sounds with a piezo What is a piezo? 'Piezo' normally refers to an electrical component which can be used to make sound, however more broadly a piezo is a component that is susceptible to the two-way piezoelectric effect where pressing or squeezing the piezo element can create a small voltage, and vice versa a small voltage can create a small expanding/contracting movement. Practically this means you can use a piezo to make sounds like a simple speaker, or act as a contact microphone. In this tutorial we'll look at wiring it up to Arduino with the Tone feature to create a melody. Wiring

24 Wiring is simple, there are just two wires, applying power causes the piezo to expand, just as applying power to an LED causes it to illuminate. 1. Ground 2. Power Getting started To get started quickly you can use one of the examples from the Arduino examples menu:

25 Read more about tone()

26 Using a Sparkfun Sound Detector What is the Sound Detector? The Sound Detector is a board made by Sparkfun electronics that provides a way to detect ambient sound levels. There are three connections on the board: Audio - This is the raw audio from the microphone. Envelope - This is a analog value representing the volume of the ambient sound. Gate - This is a digital value representing if sound levels are low or high.

27 Wiring There are two options for wiring, you can use both at the same time: Digital Wired up in digital mode the sound detector signals if the sound level is low with a LOW signal, and high with a HIGH signal. This method requires: 1. Power (VCC to 5V) 2. Ground (GND to GND) 3. Gate to a digital pin on the Arduino (turquoise wire in the diagram) Analog Wired up in analog mode the sound detector provides voltage proportional to the sound level. This method requires: 1. Power (VCC to 5V) 2. Ground (GND to GND)

28 3. Envelope to a analog pin on the Arduino (pink wire in the diagram) There are three wires: Diagram

29 Getting started Once wired, the code is that of a standard digitalread or analogread to obtain the value. Example code reading envelope #define envelopepin A0 void setup() { Serial.begin( 9600 ); pinmode( envelopepin, INPUT ); } void loop() { Serial.println( analogread( envelopepin ) ); } Example code reading gate #define gatepin 2 void setup() { Serial.begin( 9600 ); pinmode( gatepin, INPUT ); } void loop() { Serial.println( digitalread( gatepin ) ); }

30 Resources Sparkfun Hookup Guide

31 How to connect a push button or switch What is are push buttons/switches? Buttons and switches are a way of opening and closing a circuit, i.e. making and breaking a connection as one of the most rudimentary forms of sensor you can use with an Arduino. There are dozens of different types of switches and buttons, but at their most basic is the momentary push button which we'll be focusing on in the wiring and getting started sections below. However the same approach applies to these as it does to any other type of button or switch. Different types Rocker switch

32 Push button Tactile button Reed switch Tilt switch Key operated switch Rotary switch Slide switch Micro switch Toggle switch There are many different types for different purposes: Push buttons like those found in a computer keyboard are really useful for activating an action, like a start video button.

33 Rocker, slide and toggle switches work more like light switches holding their position, they can be a good way of indicating the mode of a device, such as playing video forward or backwards.

34 Micro switches can with motors to detect when it has reached the end of movement, such as in a 3D printer to stop the motor going too far over the end, or to detect if a draw is open or closed. Wiring Wiring up buttons and switches is simple, however there is a complexity you might not

35 have thought about. Although a push button like that in the diagram only has two connections, which are closed by pressing the button, you have to add a resistor to make the circuit work properly. When the button is pressed the current on one side is able to flow to the other, however when the button is released the circuit is broken and the wire to the Arduino is known as floating, the voltage is indeterminate, so we need to connect it to ground to ensure the Arduino reads 0V. It's not possible however to do this otherwise when you apply 5V by closing the circuit you would create a short circuit, instead we connect the Arduino pin through a high value 10KΩ resistor to ground, this allows the circuit to quickly reach 0V when the button is released but prevents large amounts of current flowing when the button is pressed. Getting started The following is a simple circuit that will get your button controlling the LED built into the

36 Arduino. #define ledpin 13 #define buttonpin 7 void setup() { pinmode( ledpin, OUTPUT ); pinmode( buttonpin, INPUT ); } void loop() { boolean btnstate = digitalread( buttonpin ); if ( btnstate == HIGH ) { digitalwrite( ledpin, HIGH ); } else { digitalwrite( ledpin, LOW ); } } If you want to add a toggle functionality such that one press causes the LED to come on, and another press then turns it off, so you don't have to hold the button down things get a little bit more complex. The Arduino is a powerful computer and operates many times faster than human perception, as such when the mechanical push button is closed there is a small amount of 'bounce' where the circuit makes and breaks the connection a few times before it settles, this is detected by the Arduino as multiple presses.

37 This diagram shows the signal bouncing up and down over a period of 10µS ( seconds) In effect this means that each time you press the button to toggle just once it toggles multiple times, you can fix this either with a small capacitor, or modifications to your Arduino sketch. The code here adds two major changes, first it tracks the current and previous button state through each loop meaning it can see if the button has changed from LOW to HIGH, and then adds a delay of 75ms to allow the button to settle but keep it fast enough that the user doesn't perceive this delay. #define ledpin 13 #define buttonpin 7 boolean ledstate = LOW; boolean prevbtnstate = LOW; void setup() { pinmode( ledpin, OUTPUT ); pinmode( buttonpin, INPUT ); } void loop() { boolean btnstate = digitalread( buttonpin );

38 if ( btnstate == HIGH && prevbtnstate == LOW ) { ledstate =! ledstate; delay( 75 ); } digitalwrite( ledpin, ledstate ); prevbtnstate = btnstate; }

39 Using a HC-SR04 distance sensor What is the HC-SR04? The HC-SR04 is a ultrasonic distance sensor, it uses ultrasound to send out a ping and measure how long the sound takes to come back, exactly like bats use to fly in the dark. The sensor works between 2-400cm however if the ping sound is reflected away from the sensor by an a divergent (not parallel) surface, or absorbed by a soft surface like fabric there may no measurement. There are other types of distance sensors that are more accurate for projects where needed, this is a cheap < 5 sensor, while more accurate ones are over 100. Wiring

40 Wiring up buttons and switches is simple: 1. Power (VCC to 5V) 2. Ground (GND to GND) 3. Echo to digital pin 8 4. Trigger to digital pin 7 Additionally in this diagram there is a LED attached to digital pin 13 for the getting started example code, however this isn't required for other projects.

41 Getting started This example turns on an LED when the distance measured is less than 50cm and back off when the distance goes over 60cm. #include <NewPing.h> #define trigpin 7 #define echopin 8 #define maxdistance 400 NewPing sonar( trigpin, echopin, maxdistance); void setup() { Serial.begin( 9600 ); } void loop() { Serial.println( sonar.ping_cm() ); delay( 100 ); } To use this code you will need the NewPing Library. We have a tutorial on how to install a library here.

42 Connecting a Potentiometer What is a potentiometer? A potentiometer (often abbreviated to pot) is an electronic component with three connections, the main purpose of the pot is to create a variable voltage as an input to a circuit, for example controlling how loud your speakers should be.

43 Inside a potentiometer is a large resistive area between pin #1 and #3, the middle pin #2 is called the wiper, and by actuating the pot you can select a position along that resistive area to create a proportional to the voltage between pins #1 and #3. For example if you have Ground (0V) on pin #1, and 5V on pin #3, you could select a voltage between 0V to 5V, at the half way the voltage on pin #2 would be 2.5V. Different types There are two main types:

44 Rotary Potentiometers like those found on speakers to control the volume.

45 Slide Potentiometer like those found on audio mixing desks. Wiring Wiring up buttons and switches is simple, both are fundamentally the same, however it can be tricky identifying pins #1, #2, and #3 (more on this later). At its most basic, pins #1 and #3 need to be connected to Power and Ground, for example

46 5V and GND on an Arduino. Pin #2 the wiper needs to be connected to the analog input pins: Rotary Potentiometer Wiring

47 Slide Potentiometer Wiring

48 Identifying the pins of a potentiometer The most common type of potentiometer to use is a 10KΩ potentiometer, that means the

49 resistance between pin #1 and #3 is fixed at 10KΩ or thereabouts, and that the resistance between pin #2 and either of the other two will be proportional to the position of the potentiometer rotation/sliding. In other words, using a multimeter set to resistance/ohms/ω measurement you can find the two pins that don't change at all, and measure a resistance close to the rating marked on it. The remaining leg is likely the wiper. Getting started The following is a simple sketch that will get a potentiometer controlling the LED built into the Arduino. This sketch will make the LED blink at a rate between 0ms to 1023ms, this is because the function analogread returns a value between #define ledpin 13 #define potpin A0 void setup() { pinmode( ledpin, OUTPUT ); pinmode( potpin, INPUT ); } void loop() { digitalwrite( ledpin, HIGH ); delay( analogread( potpin ) ); digitalwrite( ledpin, LOW ); delay( analogread( potpin ) ); }

50 How to connect a Light Dependent Resistor (LDR) What is an LDR? An LDR or Light Dependent Resistor is a component which restricts how much power can flow through a circuit based on how much or little light hits the sensitive part on the top.

51 Wiring To use a Light Dependent Resistor, we have to use it in combination with a fixed value resistor, the combination of these two components acts a little like a kitchen mixer tap, we can vary the temperature (voltage) by adjusting the tap. The zig-zag lines indicate resistors, the voltage output we measure with the Arduino comes from this middle point between the two, as the value of the LDR varies it changes the voltage between Ground (0V) and 5V (VCC).

52 More information about voltage dividers. Getting started The following code uses analogread() to get a integer between representing the voltage, where 0 is 0V and 1023 is 5V. The code below uses the serial port to output the value every 50ms to the Serial Monitor. #define ldrpin A0 void setup() { Serial.begin( 9600 ); pinmode( ldrpin, INPUT ); } void loop() { Serial.println( analogread( ldrpin ) ); delay( 50 ); }

53 How to use a rotary encoder What is a rotary encoder? A rotary encoder is a device used to measure the rotation of something, similar to a rotary potentiometer but not limited to how many rotations can be made, a common example of a rotary encoder is the volume dial on a car radio, which can be turned infinitely but still only goes from 0 to 100% volume. Rotary encoders come in a number of different types, typically either with or without 'detents' that is physical feedback as the encoder rotates, and in varying levels of resolution for more or less precise applications. Wiring Wiring is simple...

54 There are four wires: 1. Ground 2. 5V 3. A switch 4. B switch

55 #define enc1a_pin 2#define enc1b_pin 3boolean enc1a_prev;boolean enc1b_prev;long enc1 = 0;long prev_enc1 = 0;void Rotary In this basic encoders example workthe using encoder two switches outputswhich the value are operated as a positive slightly or negative out of phase, number meaning from it's that starting in onepositi direc Basic Example Getting started