Weekend Project: Learning Ins and Outs of Arduino

Arduino is an open embedded hardware and software platform designed for rapid creativity. It's both a great introduction to embedded programming and a fast track to building all kinds of cool devices like animatronics, robots, fabulous blinky things, animated clothing, games, your own little fabs... you can build what you imagine. Follow along as we learn both embedded programming and basic electronics.

Arduino is an open embedded hardware and software platform designed for rapid creativity. It's both a great introduction to embedded programming and a fast track to building all kinds of cool devices like animatronics, robots, fabulous blinky things, animated clothing, games, your own little fabs... you can build what you imagine. Follow along as we learn both embedded programming and basic electronics.

What Does Arduino Do?

Arduino was invented by Massimo Banzi, a self-taught electronics guru who has been fascinated by electronics since childhood. Mr. Banzi had what I think of as a dream childhood: endless hours spent dissecting, studying, re-assembling things in creative ways, and testing to destruction. Mr. Banzi designed Arduino to be friendly and flexible to creative people who want to build things, rather than a rigid, overly-technical platform requiring engineering expertise.

The microprocessor revolution has removed a lot of barriers for newcomers, and considerably speeded up the pace of iteration. In the olden days building electronic devices means connecting wires and components, and even small changes were time-consuming hardware changes. Now a lot of electronics functions have moved to software, and changes are done in code.

Arduino is a genuinely interactive platform (not fake interactive like clicking dumb stuff on Web pages) that accepts different types of inputs, and supports all kinds of outputs: motion detector, touchpad, keyboard, audio signals, light, motors... if you can figure out how to connect it you can make it go. It's the ultimate low-cost "what-if" platform: What if I connect these things? What if I boost the power this high? What if I give it these instructions? Mr. Banzi calls it "the art of chance." Figure 1 shows an Arduino Uno; the Arduino boards contain a microprocessor and analog and digital inputs and outputs. There are several different Arduino boards.

You'll find a lot of great documentation online at Arduino and Adafruit Industries, and Mr. Banzi's book Getting Started With Arduino is a must-have.

Packrats Are Good

The world is over-full of useful garbage: circuit boards, speakers, motors, wiring, enclosures, video screens, you name it, our throwaway society is a do-it-yourselfer's paradise. With some basic skills and knowledge you can recycle and reuse all kinds of electronics components. Tons of devices get chucked into landfills because a five-cent part like a resistor or capacitor failed. As far as I'm concerned this is found money, and a great big wonderful playground. At the least having a box full of old stuff gives you a bunch of nothing-to-lose components for practice and experimentation.

The Arduino IDE

The Arduino integrated development environment (IDE) is a beautiful creation. The Arduino programming language is based on the Processing language, which was designed for creative projects. It looks a lot like C and C++. The IDE compiles and uploads your code to your Arduino board; it is fast and you can make and test a lot of changes in a short time. An Arduino program is called a sketch. See Installing Arduino on Linux for installation instructions.

Hardware You Need

You will need to know how to solder. It's really not hard to learn how to do it the right way, and the Web is full of good video howtos. It just takes a little practice and decent tools. Get yourself a good variable-heat soldering iron and 60/40 rosin core lead solder, or 63/37. Don't use silver solder unless you know what you're doing, and lead-free solder is junk and won't work right. I use a Weller WLC100 40-Watt soldering station, and I love it. You're dealing with small, delicate components, not brazing plumbing joints, so having the right heat and a little finesse make all the difference.

Another good tool is a lighted magnifier. Don't be all proud and think your eyesight is too awesome for a little help; it's better to see what you're doing.

Adafruit industries sells all kinds of Arduino gear, and has a lot of great tutorials. I recommend starting with these hardware bundles because they come with enough parts for several projects:

Adafruit ARDX – v1.3 Experimentation Kit for Arduino This has an Arduino board, solderless breadboard, wires, resistors, blinky LEDs, USB cable, a little motor, experimenter's guide, and a bunch more goodies. $85.00.9-volt power supply. Seven bucks. You could use batteries, but batteries lose strength as they age, so you don't get a steady voltage.Tool kit that includes an adjustable-temperature soldering iron, digital multimeter, cutters and strippers, solder, vise, and a power supply. $100.

Other good accessories are an anti-static mat and a wrist grounding strap. These little electronics are pretty robust and don't seem bothered by static electricity, but it's cheap insurance in a high-static environment. Check out the Shields page for more neat stuff like the Wave audio shield for adding sound effects to an Arduino project, a touchscreen, a chip programmer, and LED matrix boards.

Essential Electric Terminology

Let's talk about volts (V), current (I), and resistance (r) because there is much confusion about these. Volts are measured in voltage, current is measured in amps, and resistance is measured in ohms. Electricity is often compared to water because they behave similarly: voltage is like water pressure, current is like flow rate, and resistance is akin to pipe diameter. If you increase the voltage you also increase current. A bigger pipe allows more current. If you decrease the pipe size then you increase resistance.

Talk is cheap, so take a look at Figure 3. This is an old circuit board from a washing machine. See the stripey things? Those are resistors. All circuit boards have gobs of resistors, because these control how much current flows over each circuit. The power supply always pushes out more power than the individual circuits can handle, because it has to supply multiple circuits. So there are resistors on each circuit to throttle down the current to where it can safely handle it.

Again, there is a good water analogy — out here in my little piece of the world we use irrigation ditches. The output from the ditch is too much for a single row of plants, because its purpose is to supply multiple rows of plants with water. So we have systems of dams and diverters to restrict and guide the flow.

In your electronic adventures you're going to be calculating resistor sizes for your circuits, using the formula R (resistance) = V (voltage) / I (current). This is known as Ohm's Law, named for physicist Georg Ohm who figured out all kinds of neat things and described them in math for us to use. There are nice online calculators, so don't worry about getting it right all by yourself.

That's all for now. In the next tutorial, we'll learn about loading and editing sketches, and making your Arduino board do stuff.

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Weekend Project: Loading Programs Into Arduino

In last week's Weekend Project, we learned what the Arduino platform is for, and what supplies and skills we need on our journey to becoming Arduino aces. Today we'll hook up an Arduino board and program it to do stuff without even having to know how to write code.

In last week's Weekend Project, we learned what the Arduino platform is for, and what supplies and skills we need on our journey to becoming Arduino aces. Today we'll hook up an Arduino board and program it to do stuff without even having to know how to write code.

Advice From A Guru

Excellent reader C.R. Bryan III (C.R. for short) sent me a ton of good feedback on part 1, Weekend Project: Learning Ins and Outs of Arduino. Here are some selected nuggets:

 

Solder: 63/37 is better, especially for beginning assemblers, because that alloy minimizes the paste phase, where the lead has chilled to solid but the tin hasn't, thus minimizing the chance of movement fracturing the cooling joint and causing a cold solder joint. I swear by Kester "44" brand solder as the best stuff for home assembly/rework.Wash hands after handling lead-bearing solder and before touching anything.Xuron Micro Shear make great flush cutters.Stripping down and re-using old electronic components is a worthy and useful skill, and rewards careful solder-sucking skills (melting and removing old solder). Use a metal-chambered spring-loaded solder sucker, and not the squeeze-bulb or cheapo plastic models.Solder and de-solder in a well-ventilated area. A good project for your new skills is to use an old computer power supply to run a little PC chassis fan on your electronics workbench.

 

Connecting the Arduino

Consult Installing Arduino on Linux for installation instructions, if you haven't already installed it. Your Linux distribution might already include the Arduino IDE; for example, Fedora, Debian, and Ubuntu all include the Arduino software, though Ubuntu is way behind and does not have the latest version, which is 1.0. It's no big deal to install it from sources, just follow the instructions for your distribution.

Now let's hook it up to a PC so we can program it. One of my favorite Arduino features is it connects to a PC via USB instead of a serial port, as so many embedded widgets do. The Arduino can draw its power from the USB port, if you're using a fully-powered port and not an unpowered shared hub. It also runs from an external power supply like a 9V AC-to-DC power plug with a 2.1mm barrel plug, and a positive tip.

Let's talk about power supplies for a moment. A nice universal AC-to-DC adapter like the Velleman Compact Universal DC Adapter Power Supply means you always have the right kind of power. This delivers 3-12 volts and comes with 8 different tips, and has adjustable polarity. An important attribute of any DC power supply is polarity. Some devices require a certain polarity (either positive or negative), and if you reverse it you can fry them. (I speak from sad experience.) Look on your power supply for one of the symbols in Figure 1 to determine its polarity.

Figure 1 shows how AC-to-DC power adapter polarity is indicated by these symbols. These refer to the tip of the output plug.

Getting back to the Arduino IDE: Go to Tools > Board and click on your board. Then in Tools > Serial Port select the correct TTY device. Sometimes it takes a few minutes for it to display the correct one, which is /dev/ttyACM0, as shown in Figure 2. This is the only part I ever have trouble with on new Arduino IDE installations.

Figure 2: Selecting the /dev/ttyACM0 serial device.

Most Arduino boards have a built-in LED connected to digital output pin 13. But are we not nerds? Let's plug in our own external LED. Note how the LED leads are different lengths. Figure 3 shows how many Arduino boards have an onboard LED wired to pin 13. External LEDs have two leads, and one is longer than the other. The long lead is the anode, or positive lead, and the short lead is the cathode, or negative lead.

Plug the anode into pin 13 and the cathode into the ground. Figure 4 shows the external LED in place and all lit up.

Loading a Sketch

The Arduino IDE comes with a big batch of example sketches. Arduino's "hello world"-type sketch is called Blink, and it makes an LED blink.

 

/* Blink Turns on an LED on for one second, then off for one second, repeatedly. This example code is in the public domain. */void setup() { // initialize the digital pin as an output. // Pin 13 has an LED connected on most Arduino boards: pinMode(13, OUTPUT); }void loop() { digitalWrite(13, HIGH); // set the LED on delay(1000); // wait for a second digitalWrite(13, LOW); // set the LED off delay(1000); // wait for a second}

Open File > Examples > Basic > Blink. Click the Verify button to check syntax and compile the sketch. Just for fun, type in something random to create an error and then click Verify again. It should catch the error and tell you about it. Figure 5 shows what a syntax error in your code looks like when you click the Verify button.

Remove your error and click the Upload button. (Any changes you make will not be saved unless you click File > Save.) This compiles and uploads the sketch to the Arduino. You'll see all the Arduino onboard LEDs blink, and then the red LED will start blinking in the pattern programmed by the sketch. If your Arduino has its own power, you can unplug the USB cable and it will keep blinking.

Editing a Sketch

Now it gets über-fun, because making and uploading code changes is so fast and easy you'll dance for joy. Change pin 13 to 12 in the sketch. Click Verify, and when that runs without errors click the Upload button. Move the LED's anode to pin 12. It should blink just like it did in pin 13.

Now let's change the blink duration to 3 seconds:

 

digitalWrite(13, HIGH); // set the LED on delay(3000); // wait for three seconds

 

Click Verify and Upload, and faster than you can say "Wow, that is fast" it's blinking in your new pattern. Watch your Arduino board when you click Upload, because you'll see the LEDs flash as it resets and loads the new sketch. Now make it blink in multiple durations, and note how I improved the comments:

 

void loop() { digitalWrite(13, HIGH); // set the LED on delay(3000); // on for three seconds digitalWrite(13, LOW); // set the LED off delay(1000); // off for a second digitalWrite(13, HIGH); // set the LED on delay(500); // on for a half second digitalWrite(13, LOW); // set the LED off delay(1000); // off for a second}

 

Always comment your code. You will forget what your awesome codes are supposed to do, and it helps you clarify your thinking when you write things down.

Now open a second sketch, File > Example > Basics > Fade.

 

/* Fade This example shows how to fade an LED on pin 9 using the analogWrite() function. This example code is in the public domain. */int brightness = 0; // how bright the LED isint fadeAmount = 5; // how many points to fade the LED byvoid setup() { // declare pin 9 to be an output: pinMode(9, OUTPUT);} void loop() { // set the brightness of pin 9: analogWrite(9, brightness); // change the brightness for next time through the loop: brightness = brightness + fadeAmount; // reverse the direction of the fading at the ends of the fade: if (brightness == 0 || brightness == 255) { fadeAmount = -fadeAmount ; } // wait for 30 milliseconds to see the dimming effect delay(30); }

 

Either move the anode of your LED to pin 9, or edit the sketch to use whatever pin you want to use. Click Verify and Upload, and your LED will fade in and out. Note how the Blink sketch is still open; you can open multiple sketches and quickly switch between them.

Now open File > Example > Basics > BareMinimum:

 

void setup() { // put your setup code here, to run once:}void loop() { // put your main code here, to run repeatedly: }

 

This doesn't do anything. It shows the minimum required elements of an Arduino sketch, the two functions setup() and loop(). The setup() function runs first and initializes variables, libraries, and pin modes. The loop() function is where the fun stuff happens, the blinky lights or motors or sensors or whatever it is you're doing with your Arduino.

You can go a long way without knowing much about coding, and you'll learn a lot from experimenting with the example sketches, but of course the more you know the more you can do. Visit the Arduino Learning page to get detailed information on Arduino's built-in functions and libraries, and to learn more about writing sketches. In our final part of this series we'll add a Wave audio shield and a sensor, and make a scare-kitty-off-the-kitchen-counter device.

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