cmsc838 week 01 | lecture 02 | jan 29, 2015 arduino ... · today’s learning goals experimenting...

Human Computer Interaction Laboratory

@jonfroehlich Assistant Professor Computer Science

CMSC838 Tangible Interactive Computing

Week 01 | Lecture 02 | Jan 29, 2015

Arduino, Sensing, and Processing

TODAY’S LEARNING GOALS

1. An overview of the course, course logistics, ‘Maker’ culture, the

Hackerspace, and assignments (especially IA2 & MP1)

2. Arduino basics such as digitalWrite, digitalRead, analogWrite, and

analogRead

3. Light-emitting diode (LED) basics including: LEDs only allow current flow

in one direction and that they require current limiting resistors.

4. How to read an LED datasheet and calculate the value of the resistor

5. How to use basic input components like trimpots and basic output

components like a speaker

6. How to use the Serial println functionality in Arduino to communicate

with your computer and build a simple interactive application in

Processing

You’ll get a taste of a lot of things today, some of which we will go over again ourselves; however, I

encourage you to grab components from the HCIL Hackerspace and begin playing and

experimenting with concepts, tools, and components to help you learn and reinforce your learning.

Making the invisible, visible.

First, some inspiration: you can do a lot of creative

things with simple circuits, a microcontroller, and light

Timo Arnall, Jørn Knutsen, & Einar Martinussen, Immaterials: Light Painting WiFi, https://vimeo.com/20412632

Timo Arnall, Jørn Knutsen, & Einar Martinussen, Immaterials: Light Painting WiFi

Kuznetsov et al., Red Balloon, Green Balloon, Sensors in the Sky, UbiComp2011

Kuznetsov et al., http://www.instructables.com/id/Air-quality-balloons/

air quality sensor + microcontroller + RGB LED + battery

Kuznetsov et al., Red Balloon, Green Balloon, Sensors in the Sky, UbiComp2011

Helen Evans and Heiko Hansen, Nuage Vert, http://hehe.org2.free.fr

Helen Evans and Heiko Hansen, Nuage Vert, https://vimeo.com/17350218#

power-aware cord

cord light pulsates & varies in intensity based on power draw

[Gustafsson and Gyllenswärd, CHI2005]

Arroyo et al., Waterbot: exploring feedback and persuasive techniques at the sink, CHI’05

HEATSINK thermistor senses water temperature , which feeds into a microcontroller that controls LEDs mounted around faucet

hello world intro arduino example

OPEN THE ARDUINO IDE

SELECT THE BOARD YOU ARE USING

SELECT THE COM PORT You will program your Arduino via the serial port over USB.

NOW, WE’RE READY: LET’S BLINK AN LED Arduinos typically have a single LED—often called the ‘L’ LED as this is how it’s labeled

on your board--that you can control from your sketches. The location of the ‘L’ LED is

circled below on the UNO and Leonardo. On the UNO and Leonardo, we can control

this LED via D13 (digital pin 13).

[source: https://learn.adafruit.com/adafruit-arduino-lesson-1-blink/the-l-led]

WRITING THE BLINK PROGRAM Goal: blink pin 13 (hooked up to the ‘L’ LED on the board) once every 1 second.


The ‘checkmark’ compiles and verifies the program


The ‘checkmark’ compiles and verifies the program

The ‘right arrow’ sends the program to your Arduino

THE ENTIRE BLINK PROGRAM

SOME MODIFICATIONS I paramaterized the code a bit and added my own special prefix to track global

variables.

[source: https://cdn.sparkfun.com/assets/f/4/9/2/2/Arduino_Cheat_Sheet-11-12-13.pdf]

hello world 2 blinky with external led

NOW, LET’S BLINK

OUR OWN LED

NOW, LET’S BLINK

OUR OWN LED

To do this, we need to

learn about two things:

breadboards and LEDs.

breadboards

BREADBOARDS: LOTS OF VARIETY

[source: sparkfun.com]

BREADBOARDS: HOW THEY WORK

[source: https://learn.sparkfun.com/tutorials/how-to-use-a-breadboard,]


wire1

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wire1

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[source: https://learn.adafruit.com/assets/17394, https://learn.sparkfun.com/tutorials/how-to-use-a-breadboard,]

Breadboard now flipped over (you’re looking at the back with the insulated backing peeled away)

BREADBOARDS: A LOOK INSIDE


A single strip of conductive metal from breadboard column

BREADBOARDS: A LOOK INSIDE

BREADBOARDS: A QUICK TIP


Two jumper wires used to connect the power rails on both sides. Always attach the ‘+’ to ‘+’ and the ‘-’ to ‘-’. I also like to use ‘black’ wire for ‘-’ and ‘red’ wire for ‘+’.

The power rails on either side are not connected, so if you want the same power source on both

sides, you will need to connect the two sides with some jumper wires. Keep in mind that the

markings are there just as a reference (you need not follow this convention if you have good

reason not to).

DEFENSIVE BREADBOARDING


Notice how the 5V and GND rails are only connected on opposite sides of the breadboard. This is to limit stupid mistakes!

Some ‘Makers’ choose to only connect power on one side of the breadboard and

ground on the other to reduce the chance of accidentally plugging a wire into the

wrong socket and shorting out a circuit.

BREADBOARDS: LIKE LEGOS!

[source: sparkfun.com]

Many breadboards have little nubbins and slots on the sides, and some even have

them on the tops and bottoms. These allow you to connect multiple breadboards

together to form the ultimate prototyping surface.

BREADBOARDS VS. PERFBOARDS

!=

Sometimes novice ‘Makers’ mistake breadboards for perfboards—but they are

completely different (though both allow you to hook up circuits in a semi-organized

fashion).

Breadboard Perfboard

Breadboards are great for experimenting, and testing a circuit - but once you’re happy with how it works, you’ll probably want to transfer it to something that makes it a bit more permanent. In that case you can transfer your circuit to a perfboard. Perfboards require soldering.

[source: https://learn.adafruit.com/collins-lab-breadboards-and-perfboards/transcript,]

BREADBOARDS VS. PERFBOARDS Some perfboards have the same connections and hole spacings as a breadboard


PERFBOARD USE


NOW, LET’S BLINK

OUR OWN LED

So, that’s a quick intro

to breadboards. Now

we need to learn

about LEDs.

Anode

Cathode

light-emitting diodes (LEDs)

LEDS

LEDs have polarity: the long end is the ‘positive’ lead

[https://learn.adafruit.com/adafruit-arduino-lesson-2-leds/leds]

Anode

Cathode

LEDS


[https://learn.adafruit.com/adafruit-arduino-lesson-2-leds/leds; Platt, Encyclopedia of Electronic Components]

Anode

Cathode

Helpful mnemonic: the long side is ‘+’ and the negative side is ‘-’, so consider that the plus sign would be twice as long as the minus sign if its horizontal and vertical stroke were dissembled and placed end to end.

LEDS



Anode

Cathode

You cannot connect an LED directly to a battery or voltage source. You must include a resistor to limit the current flowing through the LED, otherwise the LED could burn out!

LEDS



Anode

Cathode + -

Resistor

Long end of LED (anode) connected towards positive supply voltage

Current limiting resistor to protect LED

Current limiting resistor. An absolute must!

+ -

Resistor

But how do we know what resistor value to select?

TRIAL AND ERROR!

[source: https://learn.sparkfun.com/tutorials/light-emitting-diodes-leds]

Makers know that their LEDs require

current limiting resistors but they are often

not so exact in selecting the theoretically

optimal resistor. Instead, they pick a likely

resistor value (e.g., 330Ω) and check the

resulting brightness of their LEDs and

iterate. See flow chart.

Honestly, the easiest way to do this is via a

variable resistor like a trimpot where you

can adjust the resistance, find a good

value, and then replace the trimpot with a

permanent resistor of that value.

This works fairly well in practice but it’s

important that you understand how to

select an appropriate resistor as it involves

key circuit skills like reading a datasheet

and applying Ohm’s law.

[source: https://learn.sparkfun.com/tutorials/light-emitting-diodes-leds; https://www.sparkfun.com/quiz/60]

SELECTING A CURRENT LIMITING RESISTOR

+

-

Resi

sto

r

“Pseudo” schematic “Real” schematic

Though we’ve been using the schematic representation on the left,

the “real” electronics schematic representation is on the right. Both

diagrams represent the same circuit.


SELECTING A CURRENT LIMITING RESISTOR

Using the circuit to the left, we need to

know three values in order to determine

the current limiting resistor value:

1. i : LED forward current in Amps (found

in the LED datasheet)

2. Vf : LED forward voltage drop in Volts

(found in the LED datasheet)

3. Vs : supply voltage

Once you have obtained these three values, you can use this equation

derived from Ohm’s Law to find the value, in Ω, of the resistor:

𝑅 =𝑉𝑠 − 𝑉𝑓

𝑖

Let’s try an example…

All we really need to know has been highlighted here by Sparkfun, but let’s view the datasheet anyway as a learning exercise

LED

DATASHEET

Forward Current: how much current your LED will be able to handle continuously. In this case, 20mA.

Peak Forward Current: how much current the LED can sustain in short bursts. In this case, 30mA.

Suggestion Using Current: not all data sheets provide this, but this company recommends operating the LED at 16-18mA for best performance

Reverse Voltage: The maximum reverse voltage that the LED can sustain without damage (pay attention to this value if you often accidentally connect your LED anode to GND and cathode to VSS)

Power Dissipation: The amount of power in milliWatts that the LED can use before taking damage

[source: https://learn.sparkfun.com/tutorials/light-emitting-diodes-leds]

READING AN LED DATASHEET https://www.sparkfun.com/datasheets/Components/LED/COM-09590-YSL-R531R3D-D2.pdf

Forward Voltage: The forward voltage is the voltage drop across the LED. You must reach this threshold to turn ‘on’ the LED. In this case, 1.8V to 2.2V

Wavelength: A precise way of explaining the color of the LED, in this case its 620-625nm

LED Brightness: A measure of how bright the LED can get. The unit, millicandela (mcd), is standard for measuring the intensity of a light source. This LED has a luminous intensity of 150-200, which would make for a good indicator light (super bright LEDs can have 160,000-180,000mcd).

Viewing Angle: Different style LEDs will incorporate different types of lenses, reflectors, or diffusers to concentrate light or spread it widely.


READING AN LED DATASHEET https://www.sparkfun.com/datasheets/Components/LED/COM-09590-YSL-R531R3D-D2.pdf


Using the circuit to the left, we need to

know three values in order to determine

the current limiting resistor value:

1. i : LED forward current in Amps. In this

case, it’s 20mA.

2. Vf : LED forward voltage drop in Volts

(found in the LED datasheet). In this

case, it’s 1.8-2.2V, so let’s say 2V.

3. Vs : supply voltage. In this case, let’s

say 5V (which is a common Arduino

value)

Once you have obtained these three values, you can use this equation

derived from Ohm’s Law to find the value, in Ω, of the resistor:

EXAMPLE LED https://www.sparkfun.com/datasheets/Components/LED/COM-09590-YSL-R531R3D-D2.pdf

𝑅 =𝑉𝑠−𝑉𝑓

𝑖 𝑅 =

5 −2

0.02 = 150 Ω

EASY WAY TO TEST AN LED Just use a coin cell battery (e.g., a 3V) CR2025 or similar

SOME ADDITIONAL LED RESOURCES AddOhms #8 Current Limiting Resistors http://youtu.be/81zNcctopBI

LED Current Limiting Resistors https://www.sparkfun.com/quiz/60

Electric Power https://learn.sparkfun.com/tutorials/electric-power

http://youtu.be/81zNcctopBI



https://www.sparkfun.com/quiz/60



https://learn.sparkfun.com/tutorials/electric-power




NOW, LET’S BLINK

OUR OWN LED

So, that’s a quick intro

to breadboards and

LEDs, let’s get back to

our example.

LET’S HOOKUP OUR CIRCUIT The circuit is on the left and code is on the right

hello world 3 analogWrite and fading the LED

ARDUINO CODE: FADE THE LED ON/OFF

hello world 4 analogRead to control the fade of the LED

ARDUINO CODE: FADE THE LED BASED ON ANALOGREAD Here, we will fade the LED based on the value of the analog input pin A0

HOW TO USE YOUR TRIMPOTS! You all have breadboard friendly trimpots, let’s quickly learn a bit about them and

how to use them in our circuits!

POTENTIOMETERS ARE EVERYWHERE! Used to adjust sensitivity, balance, input, output

(especially in audio equipment)

HUGE VARIETY OF POTENTIOMETERS

SLIDE POTENTIOMETERS!

[source: https://www.sparkfun.com/products/11620]

SCHEMATIC SYMBOLS

[source: Platt, Encyclopedia of Electronic Components: Volume 1, 2012]

American Symbol European Symbol

THIS IS A BREADBOARD FRIENDLY TRIMPOT

[source: https://www.sparkfun.com/products/9806?_ga=1.88313947.1111827570.1420822056]

POTENTIOMETERS: HOW IT WORKS Inside the potentiometer is a single resistor and a wiper, which slides along the

resisitive material. Externally, there are three pins: two pins connect to each end of the

resistor while the third connects to the “wiper.”

POTENTIOMETERS: HOW IT WORKS

[source: https://learn.sparkfun.com/tutorials/voltage-dividers/applications]

Inside the potentiometer is a single resistor and a wiper, which slides along the



A

W

B


[source: https://learn.sparkfun.com/tutorials/voltage-dividers/applications]

Inside the potentiometer is a single resistor and a wiper, which slides along the



A

W

B

If the resistive material in a potentiometer is of constant width and thickness, the electrical potential at the wiper will change in ratio with the rotation of the wiper and shaft (or with movement of a slider).


A

W

B

[source: Platt, Encyclopedia of Electronic Components: Volume 1, 2012]

FADE LED WITH A POTENTIOMETER Let’s hookup the circuit first.

FADE LED WITH A POTENTIOMETER Let’s hookup the circuit first.

How would you write code to read the potentiometer value and then use this value to control the brightness of the LED?

FADE LED WITH A POTENTIOMETER The circuit is on the left and code is on the right

We can use Serial.println and the serial monitor to display our values

Super useful for debugging!

ARDUINO SERIAL MONITOR Go to Tools -> Serial Monitor

hello world 5 Fading an LED and playing a tone

ARDUINO TONE() FUNCTION Generates a square wave of the specified frequency (and 50% duty cycle) on a pin. A

duration can be specified, otherwise the wave continues until a call to noTone(). The

pin can be connected to a piezo buzzer or other speaker to play tones.

Only one tone can be generated at a time. If a tone is already playing on a different

pin, the call to tone() will have no effect. If the tone is playing on the same pin, the call

will set its frequency.

Use of the tone() function will interfere with PWM output on pins 3 and 11 (on boards

other than the Mega).

It is not possible to generate tones lower than 31Hz. For technical details, see Brett

Hagman's notes.

[source http://arduino.cc/en/reference/tone]

FADE LED AND PLAY TONE The circuit is on the left and code is on the right

hello world 6 interacting with processing

Open Processing and copy/paste the code from here:

http://arduino.cc/en/Tutorial/Graph

PROCESSING ARDUINO GRAPH

PROCESSING ARDUINO GRAPH The sketch should run right away with one exception, the highlighted part. Note: the

code below is a slightly modified version of the Arduino Graph with my own variable

names and code formatting

You must change the index in Serial.list()[4] to whatever port your Arduino is plugged into. How do you know? See next slide.

SELECTING THE RIGHT SERIAL PORT You can open up the Arduino IDE and go to Tools -> Port and simply count (starting

from 0) until you get to the COM port that is connected to your Arduino.

index 0 index 1

So, my UNO is on COM6, which will be index 1 in the Serial.list() array

SELECTING THE RIGHT SERIAL PORT The sketch should run right away with one exception, the highlighted part. Note: the

code below is a slightly modified version of the Arduino Graph with my own variable

names and code formatting

Changed to index 1

PROCESSING ARDUINO GRAPH From Serial Monitor to fanciful visualization. Note: you cannot have them both open

at the same time!

If you have the Arduino Serial Monitor open, you will not be able

to read the serial port with your Processing program!

Can you modify the code so that the graph color is based on the analog value?

PROCESSING ARDUINO GRAPH Let’s modify this graph so that the color is based on the input

SCROLLING, RESIZABLE ARDUINO GRAPH You will need to make your graph resizable for IA2

Can you draw and move a box across the screen based on the analog value?

MY SILLY DRAW RECTANGLE EXAMPLE

Photocell; $1.50 Touch Membrane

Potentiometer; $12.95

Trimpot 10k; $0.95 Flexiforce Pressure Sensor

(1lb); $19.95

MY IA2 ARDUINO GRAPH DEMO

https://www.sparkfun.com/products/8680

Playtime

cmsc838 week 01 | lecture 02 | jan 29, 2015 arduino ... · today’s learning goals experimenting...

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