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Tangible Matrix

Last updated on September 26th, 2021

Before you take your deep dive into Arduino its a good to first get a birds-eye view of what this world called tangible is all about.

In this exploration I will introduce a general framework for thinking about and creating interactive and behavioural artworks.

One of the biggest challenges students face when entering into the world of tangible is sorting how to relate lived experiences with how a microcontroller and a circuit see the world.

It is a big conceptual leap — but the tangible matrix below will give you a point of departure for this journey.

Video :: tangible matrix overview

tangible matrix

As indicated in the video, there are four basic circuit patterns or interactions that we can work with microcontrollers. That’s it. Just four.

It can be really helpful to start your tangible journey by thinking about how you experience the world. Two really important systems shape how you become aware of and move through the world. They are your sensory systems and the skeletal muscular system that enables movement.

Inputs

Let us begin by considering your sensory systems and let us describe those as inputs. Sensory systems — vision, hearing, taste, touch and smell — are how you bring information into your body. We also have systems that lets us evaluate our internal state — our sense of balance, proprioception (kinesthesia) or our sense of our own movements, thermoception (temperature), itch, muscle stretch and hunger. Each of these is a pathway for us to gather information about our body and how it relates to the world.

Inputs are circuits or contexts that bring information into our system.

Outputs

We can also consider the ways we move, behave and impact our environment. We will call these outputs. These may include sounds, movement, chemical signals (pheromones), sweat, exhaled breath or even waste products.

Outputs are circuits or contexts that push information out of our system.

How does an Arduino see the world?

Your Arduino (Uno, microcontroller) also has inputs and outputs. But it has a very constrained way of accepting information and generating actions.

Microcontrollers can only listen to voltages and sometimes currents. We can combine electronics (circuits) with our microcontroller to create all kinds of input and output based experiences.

And despite all of that diversity, all of thousands (millions?) of circuits that are possible — and it amazing what is possible — ALL of the circuits fall into only two categories: digital or analog.

Digital

Digital refers to circuits that can only be in one of two states — on or off. We use some synonyms for this, we might say HIGH or LOW, or 1 and 0, or true and false. Think about a simple light switch in a room — it can either be on or off.

Binary (anything that has 2 parts) is the number system associated with these 1s and 0s. So digital means two states; 1,0 and is identified numerically with binary.

Binary Voltages

When we describe a digital system as being in the OFF, LOW, FALSE or 0 state we talk about its voltage being equal to zero volts. In a circuit that means it is associated with the negative side of your battery or power supply (bottom of the waterfall).

When we describe a digital system as being in the ON, HIGH, TRUE or 1 state we talk about its voltage being equal to whatever the plus volts is in your power supply (in Arduino this equals 5V max). In a circuit that means it is associated with the positive side of your battery or power supply (top of the waterfall).

Analog

The other kind of circuit we will encounter is analog. Analog circuit are much more human like. In fact, nothing in the human body is digital.

Analog circuits refer to the worlds of continuous gradation. This could be volume of music, speed control or a light on a dimmer switch. Analog is all the shades of grey that make experiences great.

Analog Voltages

Analog circuits require a different way of thinking about compared to digital systems.

Analog circuits can be in at any voltage between ground ( bottom of waterfall) and plus voltage (5V for Uno, top of waterfall). So we can think of analog circuits as having power waterfalls of different heights.

Summary

There are only four kinds of basic contexts that we need to consider when working with microcontrollers like the Arduino Uno. Those contexts are defined by direction of electricity flow; input and output, as well as the number of voltage states a circuits can achieve; 2 for digital, infinite (from zero to +V) for analog.

The tangible matrix above summaries these contexts and offers basic examples of each context.

Explore each context in the related building blocks:

First Circuit :: Breadboard Edition

Last updated on September 26th, 2021

In this exploration we are going to take your Alligator Clip Circuit as a starting point and move it onto a breadboard.

Before you Begin

Before you start his build you should have completed the Alligator Clip Circuit — and all associated Building Blocks. You should also review the Breadboard Building Block.

Breadboard Logic

Let’s quickly review the inner workings of breadboards (complete the Breadboard Building Block if you need more details). The surface of the breadboard is covered in small holes called tie points. These holes accept wires and component legs allowing quick, temporary and stable connections among parts.

It is vital that you memorize the internal pattern of connections of your breadboards.

Bread board and its internal connections. Front and Back views of a BB.

Power Rails ( Busses )

Power rails run full width, top and bottom. They are labelled with blue and red silk screen. These labels indicate power connections. By convention RED rails get connected to the POSITIVE side of your battery pack or power supply and blue rails receive GROUND connections.

The Great Divide

I like to call the gap in the middle of the board the great divide. It is spaced so that integrated circuits (chips) can be easily fit onto the breadboard. the tie points above and below the great divide are associated with numerous terminal strips.

Terminal Strips (Middle)

The array of tie points in the middle of your breadboard cover rows of terminal strips. The terminal strips are arranged side by side. They do not cross the great divide and they do not connect directly to power rails.

Circuit Representations

During this course I will share circuit representations in several formats.

Schematics

The most reliable of these is the schematic. This representation gives a topological (relational) map of the components in a circuit and how they should be connected. Schematics do NOT described the physical orientation of parts, what sort of wire or conductive material to use, how much of that wire to use, nor where on a breadboard to place your parts. Schematics only describe electrical connections.

Diagrams and Photos

I also use photos and diagrams (the later usually made with software called fritzing). These hold the same basic information as a schematic but also define a specific instantiation of the circuit. These will show specific placement of parts and real world orientations.

circuit representations, photo, diagram,schematic

Lets Build

We are now ready to start building our first circuit :: breadboard edition. This circuit is the hello world of electronics. It is a proof of concept circuit as well as a placeholder circuit — as we will learn later in term.

schematic of LED wit current limiting resistor

Our first circuit is a simple LED with current limiting resistor.

Goal of this build.

Remember, circuits are circles of conductors. The goal of this build is to get your LED glowing on a breadboard.

Parts you will need

  • battery holder — loaded with AA batteries.
  • wire battery clip
  • LED-single color ( red OR green OR blue )
  • fixed resistor (1k — what color bands is that?)
  • resistor chart or worksheet
  • a breadboard
  • breadboard

Video :: First Circuit Breadboard Edition

Get the slides

ex_digitalOut_slidesDownload

Is it Glowing ? Celebrate!

Take a moment to celebrate if you got to this point and your LED is glowing. This may be a happy candy moment — your call. It is a simple circuit but it has a ginormous learning curve. Bask in the light of your little LED and know that it is just the start of big things to come.

Troubleshoot — mine didn’t glow 🙁 — Yet.

If your LED is not yet glowing don’t despair. Most circuits don’t work on the first try. Here are some things to try to test and troubleshoot your circuit.

  • Disconnect your battery
  • Is the battery hot ?
    • feel it and make sure its cool. If its HOT you have a short circuit — a direct path from battery positive (battery clip red wire) to battery ground (clip black wire). FIND the SHORT solve it before you continue. This is not always obvious — and shorts can be dangerous — if you can’t find the error and your battery keeps getting hot — disconnect and reach out for help (see below).
  • Is the battery cool?
    • assuming your battery is cool to touch, you likely just have a misplaced connection on the breadboard OR your LED is in the wrong way.
    • FLIP the LED — remember LEDs have polarity, and act as gates. Current can only flow through them one way. IF that doesn’t solve it flip it back (make sure flat side, short leg faces ground).
    • If LED is right, this is next big point of error — Check that the LED and resistor legs that are supposed to connect are in the same terminal strip. And that they are on the same side of the great divide. They should be side by side in one short row.
    • check your battery pack did you put each battery in properly? Make sure each battery is alternating direction with the +ve on each battery aligned with +ve in the holder? Check the battery clip — is it securely connected and seated (did you hear it ‘snap’ on). Check the wire ends of your battery clip — are they frayed? Do they insert easily? Try the other clip in your kit.
  • Still not Working?!
    • Double check the whole circuit — Start at red wire on your battery clip, make sure it is connected to a red rail on your breadboard.
    • Check that the long leg of the LED is in the RED rail and is seated well.
    • Confirm that the short leg of the LED is securely placed in a tie point.
    • Confirm that the first resistor leg is on the same terminal strip as the short LED leg. (Resistors do NOT have polarity so flipping it won’t change anything — but good idea).
    • Confirm that the second resistor leg in securely connected to the ground rail on your breadboard.
    • Confirm that the ground wire is connect to the same rail as the resistor leg.
  • Really, still not working … ok, let’s change some parts.
    • try a different LED there is a slim chance the one you have is broken.
    • try a different breadboard — sometimes these just don’t hold wires right. If this fixes it — throw the first breadboard out.
    • try your other battery holder — move all the batteries to the other holder try again. Keep the first one it may have just been improperly loaded.
  • Still? #$%^@$%! I feel your frustration
    • eat one of the candies in your kit (its time).
    • reach out — ask a friend, hit discord, go to the virtual makerspace, email steve

Arduino :: Introductions

Last updated on September 6th, 2024

Understanding the Arduino Ecosystem

The Arduino platform is made up of a combination of microcontroller boards (hardware) and the Arduino IDE (Integrated Development Environment, software). There are countless variations on boards that have a wide range of capabilities. There are several official options for the code environment and several other platforms that support programming Arduinos.

In this course we will be using Arduino UNO microcontrollers and the latest version (2.x) of their desktop IDE.

Part 1 – Hardware :: What’s an Arduino ?

Microcontrollers are small computers designed to respond to and control connected circuits. These are distinct from microprocessors (the kind of computer chip inside your laptop of desktop). The microcontroller included in your kit is an Arduino Uno.

The Uno is a microcontroller chip (Atmega328) and some related hardware (USB, power regulation, breakout headers) all attached to a single board making it easy to use and program. The Uno is very popular in creative and maker communities. It is an excellent way to start exploring tangible.

Like all of our hardware components we need to be able to identify the device — or in this case it various hardware features, know if electrical limits and learn its representations.

Representation(s)

The Arduino symbol is complex, reflecting the sophistication of the device. We will come to understand all the parts over several weeks.

Arduino Power Limits

One must take care when powering the Arduino. It is a 5V max device. It can be very safely powered by USB — which is designed to provide 5V, 1A to connected devices.

When powered by your battery packs (9V) — the only safe way is to use your battery clip with the barrel jack.

Getting to know your Uno

Required Parts

  • Arduino UNO
  • USB cable
  • Battery Clip with Barrel
Uno
USB cable
Barrel Jack Battery Clip

Landmarks

The Uno has several features that you should take the time to get familiar with. They are highlighted in the image below.

Video :: Getting to kNow Your Arduino

Get the slides

ex_digitalOut_slidesDownload

Part 2 – Software :: What is the Arduino IDE?

The second component of the Arduino system is the programming environment or IDE.

Context of tangible Coding

Before we download and set up the Arduino environment, we should take a moment to think about how it relates to other code contexts you may have used in the past.

Different computer languages and platforms have been developed to solve different problems.

The problems we want to explore in this course revolve around themes of tangible computing: how can we build an experience that knows when people are present? How can I make that thing move? How can I built an object that responds changes in temperature?

All of these examples exist in the real world (not in a web browser or on a screen). The Arduino platform was developed to explore exactly these real world experiences.

Where is the code?

Arduino code is compiled and embedded. As a result, there are a few programming steps that you may not have experienced on other platforms. This is especially true if you are coming from a web (P5JS) background, or from P5JS’s parent platform Processing.

Like many other platforms you will write code in a glorified text editor. However, to make your code run you need to get it inside your Uno (microcontroller).

The first step in this process is compiling. Compiling is an automated process that takes the Arduino-language syntax that you typed and converts it into a machine readable format. Syntax error checking happens at this stage. So typos and language bugs will often be caught here.

Once compiled, the code is UPLOADED into the Uno. Uploading literally moves the compiled machine code from your programming computer into the chip on the Uno board. Once uploaded it runs automatically. You will solve semantic or experience errors and bugs at this stage.

Required Software

You can download the required free software from the Arduino site.

Arduino software is open source and donations are requested. But you can hit the <Just Download> button.

Here is a quick walk through of the process (2024).

Once you have the software downloaded and installed you should test your tool chain.

Comparing Arduino 1.x and 2.x

Make sure you get the latest Version 1.X desktop IDE for your platform (at time of writing this was 1.8.16). We will not be using the Web Editor or the Version 2.0 IDE — which is in Beta. (You are encouraged to check out the V2.0 IDE as it will be standard very soon, but i will teach from 1.X).

As of 2024 we will use Arduino IDE 2.x in our introductory class. This version is a fork of the VSCode environment, so if you have experience there you will see some similarities (and a few differences).

This means that moving forward, older videos use a different interface than the one we are using in class. Some things are in different places. At first you may find the translation between versions a bit overwhelming – but it should be quick to overcome.

To help in this transition, I have made a video which highlights the difference between V1.x and V2.x for board selection, port selection, serial monitor access and functioning, and serial plotter access. You may want to watch it now or later as you move through this introduction.

As mentioned in the video — this is a bit chicken and egg — seeing the comparison before you know the tasks. You may decided to come back to this video at various times through out the course.

GET to know the Arduino SOftware (IDE)

This video was made in 2020. The above video will help you figure out differences if you are unsure.

There is a section in this video (below) that shows you how to turn on line numbers and code folding — these are both enabled by default in the 2.x versions. So nothing to do there. On OSX you can’t turn them off anymore, I assume that is the same across platforms ( let me know if I am wrong, or if your platform is different).

Toolchain overview, Upload code, Blink an LED.

In this video near the end, there is a reference to an assignment called a Circuit Selfie. In 2024 these are now called ARTifacts … check D2L for specific course tasks, because these have changed since the pandemic years.

Checkout the Arduino language

The Arduino language is a subset of C and C++ with some hardware specific (contextual) additions. Take a few minutes to check it out. It has many structures that should be familiar.

Advanced Considerations

If you are new to all of this, feel free to ignore this paragraph.

If you have coded C or C++ or even C# for screen based contexts (apps, phones, gaming) you will notice some features are not available. Arduino Unos are a very basic, single threaded, 8-bit RISC architecture. They do not support screens or multitasking. There is also no math co-processor so INTs largely rule the day.

Going Further

There are thousands of pages and sites dedicated to learning Arduino. Google is your friend but there are caveats. A lot of information dates very quickly. Older posts are very likely no longer current. These may be great for background, but specifics often change. If you search instructables — and you absolutely should — note that info there is not fact checked — not all instructables are complete, nor do they always make sense or even come to the conclusion suggested by their titles. That said, I am learning new stuff there all the time.

The Arduino Getting Started page gives a great overview of all the available boards (when we first used Arduino in this course there was only one board!)

All the built in examples ( board specific) are well documented and could be places to dive in.

Check out the official Arduino Playground for loads of detailed information. It will go well beyond this course.

If you want to go beyond our kits Sparkfun has lots of Arduino info. BUT BE AWARE that they are US based so buying directly comes with border broker and currency costs. Perhaps use this link for info only and check out some buying tips here before ordering form the states.

Buying Parts in Canada

Last updated on September 22nd, 2024

This is a list of resources for buying additional parts if you so desire.  You should have most ( all?) of what you need in your kit but there are tons of other parts out there and you may want to explore some.  these are not endorsements — simply provided for reference.  Comparative shopping pays in this space.  

Canadian (shipping but no duty or import) 

Sometime in 2024 – Creatron seems to have crumbled. This is a big loss – they could be a bit socially cold and occasionally condescending, but they had a great range of products. Creatron (Toronto)  — https://www.creatroninc.com/ — post pandemic I think they are down to one store in Toronto.

As of sometime in 2022 or 2023 Elmwood Electronics has merged with pishop.ca This has resulted in slightly higher ticket price — but Canadian dollars and no exchange. Elmwood — https://elmwoodelectronics.ca/ — sell US suppliers (Sparkfun) without the direct import costs   — slightly higher prices than you will see on US site — cause they paid import/ shipping for you, and exchange.

You can still go to Supremetronic. 290 College St, Toronto, ON – (just west of Spadina)

Note: Supremetronic is part of Home Hardware and is located in the basement of this Home Hardware location.  AFAIK they are not online — but post-COVID they are an adventure and are totally worth a trip — i have not gone recently — let me know how it goes.

Robotshop ( Montreal ) — https://www.robotshop.com/ca/en/?___store=ca_en&___from_store=us_en

Solarbotics ( Calgary ) — https://solarbotics.com/

Buy A Pi—  https://www.buyapi.ca/. — mostly R-pis which are not the same thing.  But also some other interesting parts.

Canada Robotix — Toronto — https://www.canadarobotix.com/

Sayal — https://secure.sayal.com/STORE2/shop.php

This is a good list — I have not used all suppliers listed here but give them a try. http://makercanada.ca/

Warehouse Suppliers

These companies are massive suppliers who sell to individuals.  Its an epic experience but you can save some money if you know what you want — these places take a bit search practice.  These have Canadian and US sites — check your location when shopping. 

https://www.digikey.ca/ — most of your kit came from here

Mouser Electronics

Newark Canada

US Suppliers

Shipping, duty and exchange are all ADDED costs for these.  If you find something on these sites, search the suppliers above before you buy and compare prices. 

Sparkfun. https://www.sparkfun.com/

— this is one of the original shops that supply hobby electronics — huge range of parts — lost of ideas.

Ada Fruit.  https://www.adafruit.com/

— this site has great tutorials and supports.  They are worth a look.  Arduino used to be their bread and butter but they have created their own product line — so older tutorials are more relevant to this course than newer ones, but may be dated in some cases.

— they are the originators of LED strips and rings — which are really cool and expressive devices — but they can be expensive.  

Buttons and Switches

Last updated on September 26th, 2021

Buttons and switches are basic parts found in many physical user interfaces. They come in many shapes (form factors) and sizes. Switches and buttons can be used in stand alone electronic situations or combined with code (Digital Inputs). This Building Block will introduce you to the two basic examples of buttons and switches that we have in our kits.

Switch Basics

Find the basic switches in your kit and set them out in front of you. You should be able to find push buttons (left) and slide switches ( right ). Once you have them out explore the switches, get a feel for how they move and slide.

Simple switches in our kits.

What are Switches?

Switches are devices that allow us to make and break connections within a circuit. Our switches are small and can only switch small voltages (5V or 9V max) and current (milliAmp level – mA). We will use them to control inputs into our Arduino.

Switch Representations

As mentioned above, switches come in many shapes and sizes. While we can represent switches in many ways, you will commonly see the following symbol to indicate a simple switch.

simple switch symbol

More complex switches will reorganize the above symbol to reflect their internal connection patterns.

You may also see more diagrammatic versions of the switch. These indicate something about the physical structure as well as the electrical connections.

I may use the following for push buttons :

push button symbol


And this for our slide switches.

slide switch symbol

Let’s explore our switches in circuits to build an understanding of how they work and what they do.

Required Parts

  • switch
  • button
  • breadboard
  • LED
  • 470 ohm resistor (current limiting resistor)
  • battery pack
  • wire battery clip
  • slide switch
  • breadboard

Video

Please note — In an effort to reduce e-waste we decided to no longer include the 37-sensor set (mentioned in the video) in every individual kit. Many of these were not used by most students. These kits are available to borrow from the makerSpace (post-Covid, once we return to campus).

Get the slides

bb_switches_slidesDownload

Building A Switch Circuit

Here is a simple circuit that can be used to illustrated how switches work. It is also a great circuit to test a switch’s function independent of code.

simple button circuit schematic.

Using a Switch as a Digital Input

Switches are key elements in making digital inputs to an Arduino (or any microcontorller). For this cicrcuit, you will need a breadboard, a 10K and a 1k resistor and a jumper wire.

Here is the circuit:

simple digital input.

For a full explanation of this circuit refer to your digital input cheat sheet ! You can also find a lot more information at the Digital Input page.

Going Further

Switches come with a truly impressive amount of jargon. It is very specific, and once you get over the shock, actually useful. But it can make getting to know these devices overwhelming. In the sections below, i will intorduce you to some terminology you may encounter as you go further.

Momentary / Maintained

Switches may be distinguished by the kinds of movents built into them. Momentary switches are those that ‘bounce back’ or return to their starting position when released. Our buttons are momntary.

Maintained switches, hold their position when released. You can feel this action with our slide switches.

There are some switches, such as those in relays, that are momentary but are controlled by elecrticity — not human engagement.

Normally Open / Normally Closed

Momentary swiches amy also be categorized by their electrical state when not pressed. Our buttons for example are OPEN when not pressed and CLOSED when we force the plunger down. THey are called Normally Open (NO).

Some button are closed when resting and are opened when we press them down. These are called Normally Closed (NC).

WHile the wiring for these will be similar, think about how this affect circuit behaviour. A normally closed switch will allow curent to flow when NOT pressed. While a normally open switch will only allow current to lfow when pressed (closed).

Throws / Poles

More abstract and advanced is the idea of poles and throws. Poles indicated the number of circuits a device can controlled. Throws indicates the number of postions to which the poles can be connected.

Our buttons are very simple single pole (one circuit), single throw (one postiion) switches. We abbreviated this SPST.

Our slides are single pole (one cirucit), double throw (two positons) — or SPDT.

Learn alot more about poles and throws in the links below.

Related Links

Switches @ sparkfun.

Code of Conduct

Last updated on February 7th, 2022

tangible is a community of learners. One of our core beliefs is that everyone has something to share. Comments and forums provide one channel for engagement and dialog. Your actions must meet our basic expectations outlined below.

0. Kindness: Be kind to everyone and treat them as they want to be treated. Virtual space is not an excuse to be a jerk. EVER. Online spaces still have real world consequences (outlined in school policies).

1. Inclusion: Be committed to decolonization and antiracist practice. Be open to listening & learning.

2. Boundaries: Respect the boundaries of everyone in the comment sections of this site.

3. Take care: Get outdoors, drink water – 8 cups, sleep – 8 hours. It makes everything tangible so much better.

4. Feedback: When offering critical feedback, do so with the belief that people are here to learn; when receiving critical feedback, listen to others with a willingness to learn.

5. Support: Do your best to support each other — think about what you are saying BEFORE you post.

First Circuit :: Alligator Edition

Last updated on September 26th, 2021

In this Exploration you are going to make your first simple circuit. The goal is to make an LED glow.

Some of you are going to shoot straight to the video and get building. IF that’s your tactic — make sure you also come back and complete the Building Blocks listed below, if you have not already done so.

Before you begin

Before you start this build you should have reviewed the following Building Blocks:

I suspect some of you will just dive right in — if that’s your plan, make sure you come back and review the info above — it will really help you to understanding this build — and all that follow.

Parts you will need

  • battery holder
  • 6 ‘AA’ batteries
  • wire battery clip
  • LED-single color — your choice, Red or Green or Yellow.
  • fixed resistors – 1kΩ ( what are the color bands ) ?
  • alligator clips

Video :: First Circuit – Alligator Edition

Troubleshooting :: I didn’t glow 🙁 YET)

Some ( ok, a lot, or most, maybe all ) of the time, circuits just don’t work on your first try. This is not a give up moment — this is a check your work moment!

The single biggest skill you will need to master in the world of tangible making is troubleshooting. Circuits fails are not because I have evilly planned to give you something dysfunctional (tho we may do that together live) — but because electronics is often an all or nothing event — either you build it right, or you don’t. When you are starting out lots of things can go wrong. That is OK. Check the video below to see how you can solve your circuit and get your glow on.

The take away — tenacity matters.

Still stuck ? Reach-out — hit discord, come to hackNight, ask in class.

Going Further

Reflect: Which side of your LED faced ground when it successfully glowed?

Did you try all the LED colors in your kit?

Can you make a version of this that uses ALL of your alligator clips to make a giant circuit-hoop?

LEDs :: Light Emitting Diodes

Last updated on September 5th, 2024

What are LEDs?

LED stands for Light Emitting Diode. When powered correctly LEDs glow different colors. Some LEDs have only a single color while others have multiple color channels build in. Multi-channel LEDS can be mixed to create almost any color imaginable.

What do LEDs want?

  • LED’s just want to glow.
  • LED’s want only a SMALL amount of current — and they need it going in the right direction.
  • They want the protection of a current limiting resistor.

LED Representation

The LED symbol combines a standard diode symbol (not all diodes glow) with outward pointing arrows to indicate light being emitted.

LEDs act like one way gates !

All diodes — whether they glow or not — act as one way gates. They only allow current to flow through them in one direction. We call this requirement for electrical direction polarity.

When an LED is given power in the wrong direction it will not light up (burn). So you must make sure to place the LED properly in your circuit.

Required Parts

At this point, you just need to grab your bag of LEDs.

Video :: Intro to LED landmarks

Slides: Grab a copy

bb_leds_slidesDownload

Flat Side to Ground!

Our kit’s single colored LEDs have two physical characteristics that will help you figure out which way the electrons are allowed to flow and therefore how to place them in a circuit.

The best way is to determine polarity is to examine the bottom of the LED cap or lens (the colorful plastic bit). If you look very carefully at the bottom of the lens you should be able to find a flat region. You may have to feel for it with your fingers. The leg immediately below the flat region should always be connected towards (closer) to the ground side of your circuit.

An alternate way to figure out polarity is too look at the length of the legs of your LED. A fresh-from-manufacturer LED will have one long leg and one short leg. The short leg should be placed in a circuit facing ground. (BTW — eventually you or some ruthless electronics fairy will trim the legs of your LED and then the whole leg length system is completely useless — so make sure you can find the flat side).

Last, you may be interested to know that physicists gave the legs fancy names. The long leg is called the anode, the short leg called the cathode. If you can remember flat side to ground, I will forgive you for not remembering the fancy physics names.

led landmarks

All of this information is actually also summarized in the LED symbol. The triangle in the symbol points in the direction of current flow and the straight line right after the triangle acts like a wall or dam — it prevents flow coming from the flat side. The straight line also indicates the flat side of the LED lens. You have to admit, that’s pretty cool.

Note — in the image above, imagine current flowing from left to right.

Going Further

Check out Forest, an LED based installation by Micah Elizabeth Scott, created in collaboration with New Media students in 2015.

Also, Marshmallow Clouds, by tangible interaction and New Media students.

Ready to make an LED glow? Give this first circuit build a try if you have alligator clips — or — try the breadboard version of the circuit if you don’t!

Fixed Resistors

Last updated on September 26th, 2021

Resistors are a fundamental component in electronics and we will see them in almost every circuit we build. They come in a wide variety of flavours ( as you will soon see) and your kit includes a number of examples.

What is resistance?

Broadly speaking all materials can be categorized as conductors or resistors according to their ability to let electrical current flow. Resistors are those materials — or components — in a circuit that inhibit or resist the flow of electrons.

Resistance is the measure of opposition to current flow. Its unit is Ohms and we represent resistance with the greek letter omega (Ω).

What do Resistors Want?

Resistors are placed in circuits to protect other components (they do other stuff but that will get us started). They are important because all of the components in our kit have electrical limits (including resistors). If you exceed the limits you can damage components.

Resistor Representations

Through out this course you will see resistors represented in photos, diagrams and schematics. There are two primary schematic representations for fixed resistors — i tend to use the zigzag one — some software packages use the rectangle.

Note that the specific value ( 1KΩ or 47kΩ) of the resistor is also given beside the resistor symbol. The R1 and R2 labels are tied to parts lists — they are not usually included in hand drawn circuits. I will leave them out most of the time.

Identifying Fixed Resistors

When starting out, one major skill you need to develop is resistor identification. Identification has to do with determining the size of a resistor. Where resistor size refers to the amount of resistance, not the size of the physical package. In fact, you should notice as you work your way through this Building Block that all of our resistors are the same size physically. But the resistances they provide differ by several orders of magnitude.

We determine resistor size by decoding the color bands on their bodies. The video below will explain the process.

Required Parts

You will need your fixed resistors, your resistor color chart and the resistor worksheet from your kit. OH — you also need your crayons! (I don’t have a crayon pic yet.)

  • resistor chart

Video :: Intro to Fixed Resistors

Slides: Grab a copy

ex_digitalOut_slidesDownload

Going Further

Why Ohms?

Many more details from Sparkfun.

About

Last updated on September 26th, 2021

Welcome to tangible.

This site was created by steve daniels, artist and instructor in the New Media program at X-University.

The site is maintained by steve with contributions from the New Media makerSpace staff and students of RTA 321: Introduction to Tangible Media.

You can reach steve by email here.