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The Arduino Boards

in Getting Started

This tutorial, continues with the quest of learning more about programming and electronics.  We will choose the Arduino Uno board for our tutorials. The Uno is the baseline Arduino board, being the one around which other Arduino boards are designed. Besides that, the Arduino Uno Board is an excellent board if you would like to begin with electronics and coding. Furthermore, the Arduino Uno is a cheap board, so if you do something wrong it will cost you a few dollars to start over again.

Therefore, the Uno is a great place for us to start with.  It’s also a fantastic launchpad if you decide to move on to other platforms in the future.

In this tutorial, we’ll do a high-level overview of the Arduino Uno hardware. Specifically, we’ll cover:

  • The Concept of an Arduino Board.
  • The Three Types of Pin Header Rows: Digital, Analog, and Power.
  • A summary of all the Arduino Uno Board elements.

The Arduino Board

The Arduino board is a microcontroller board based on the ATmega328P. It has 14 digital input-output pins, 6 analog inputs, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything you need to start with microcontrollers. Below is a picture with all the key elements of the Arduino Uno Board. We will discuss all of these elements in this tutorial.

Digital Pin Headers

There are three categories of headers: digital, power, and analog headers. The first one we’ll discuss is the digital category.

Digital pin headers make up the longest row on the Arduino board.

They are numbered from zero to 13.  That means there are a total of 14 digital pins that we can use.

Digital pins are used in one of two ways.  They can be used as inputs to do things like reading a voltage.  Otherwise, they are used as outputs, such as applying a voltage.

When they operate as an input, they can only read two different voltage states – HIGH or LOW.  The same is true when they act as outputs.  They can only output two voltage states – five volts (HIGH) or zero volts (LOW).

Just as in anything else in life, there is an exception to this.  You’ll notice that some of these pins have a little mark next to them.

There should be six of them, located at pins three, five, six, nine, 10, and 11. These specific pins allow you to use a technique called pulse width modulation, or PWM.

PWM is a technique that we’ll dive into in later tutorials.  It enables us to use digital pins in such a way that they appear as though they are outputting a varying amount of voltage.

Again, we’ll get into PWM in much greater depth later.  Right now I just want to point out those pins, and why they are special.

I also want to point out two other pins.  Notice that pins zero and one have a “TX” and “RX” next to them with little arrows.  That stands for transmitting and receive.

If you have the Arduino hooked up, and it’s supposed to be communicating with the computer, you should see these blinking.  If not, it’s a good indication that you probably don’t have the Arduino set up correctly in the IDE, and communication is unsuccessful.

Lastly, pin 13 is also worth noting. That is where an onboard LED is attached.  You can use that LED as though it were externally connected through a resistor to the Arduino.

Analog Pin Headers

The next category of headers is analog pin headers.  These are labeled A0 through A5, giving us six analog pins.

As you might have guessed, “A” stands for analog.

Before we said that digital means discrete states – either high or low, one or zero, black or white.  However, analog is a lot more colorful.

When we say something is analog, it means that it can be in any number of states.  Analog embraces all of the various shades of gray between black and white.

Many sensors create analog signals.  They’re not just on or off.  They can be all of the states in-between.

However, our integrated circuit really only knows digital states.  Therefore, the microcontroller handles analog inputs by using a tool called an analog-to-digital converter, or simply an ADC.

The ADC is part of the integrated circuit, built right into the chip.  The analog pins have access to it.

The ADC takes all of the variations in an analog signal and cuts it up into discrete steps.  In other words, instead of having an endless list of possibilities from your low to high limit, the ADC would cut that expanse from the low value to the high into a certain number of “chunks”.

In addition to being able to use the ADC, analog pins can also act just like digital inputs or outputs.  So, they are very versatile.  

Power Headers

The last row of pin headers is the power header row.  They are next to the analog headers.

There are only a handful of pins I want to point out right now.  The first one is labeled “5V”.

That stands for five volts.  If you have the Arduino hooked up to the computer via USB, or if you have external battery power applied, this pin can provide five volts to a circuit.  We’ll be using this pin extensively throughout the course when we’re setting up our circuits.

The pin next to it is labeled “3.3V”, which stands for 3.3 volts.

Arduino Board Elements

  1. USB-Power : the Arduino Uno board needs them through a USB Cable from the computer.
  2. Barrel Jack, POWER: The board can be powered from AC main power supply, such as batteries by connecting it to the board.
  3. Voltage Regulator: this is used by the Arduino Board to regulate the voltage given to the board by the USB-Power or the Barrel Jack.
  4. Crystal Oscilator: the Arduino board uses this to calculate time.
  5. Reset Button: you can hard reset your Arduino by pushing the button. In contrast, you can also use the PIN with the name RESET to attach an external reset button.
  6. 3.3 Volt output: supplies 3.3V output. Most of the external components used with Arduino will work between 3.3V and 5 volts. Examine the datasheet/details of the component to ensure that you use the right voltage?
  7. 5-volt Output: supply 5-volt output to external components.
  8. GND (GROUND): there are several GND pins on the Arduino Uno board. You can use any of those to ground your circuit.
  9. VIN PIN: equals the input voltage to the Arduino board when it is used as an external power source. You can supply voltage through this pin to components as if you are supplying voltage via the power jack.
  10. ANALOG PINS: there are 5 analog pins on the Arduino Uno board. These pins transform analog signals from sensors into digital readable values that can be read by the microcontroller
  11. Main microcontroller: this is where the brains of the Arduino is. In case of the Arduino Uno board,it uses an ATMEL chip.
  12. Power LED indicator: this LED should light up when you power your Arduino Uno board.
  13. Digital Pins: the Arduino Uno board has 14 digital pins. 6 pins, with “ ~ “, provide PWM (Pulse Width Modulation) output. See the tutorial about Pulse Width Modulation for more info. The digital pins read logic values (0 or 1) as input or as digital output to drive various modules like relays, LED’s, etc.

In the next tutorial, Arduino Tutorial: 1.2 How to use a Breadboard, you will learn about the breadboard and the wires that we will use in our lessons. After that, you will be able to make your first project

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