02) What is the Arduino?

What is the Arduino?

There is not just one Arduino, but many different types such as:

  1. Arduino Mega

  2. Arduino Bluetooth®

  3. Arduino Pro Mini

  4. Arduino Diecimila [2009 in Italian]

You will probably be using the Arduino Diecimila, unless noted otherwise.


On the left, we have the USB jack which will be used with the communication between the board and the computer. As well as the Power jack. Please only use one method at a time, as using both will damage the computer's USB port if not caught by the port surge protector.

On the top we have mainly Digital pins. Digital pins are what makes the Arduino what it is! The Arduino board can manipulate each individual pin using its uploaded code. It can manipulate each pin by either outputting voltage, or by interpreting the voltage. These pins are labeled from 0 to 13 (with a ground [negative] and AREF pin on the very right). Some pins are special, including pins 0,1, and 13.

Pins 0 and 1 should not be used unless suggested otherwise. The reason being is that they carry special properties of TX and RX which stand for Transmit and receive. When used, the ports interfere with the data transfer to and from the computer (which also leads to corrupted uploads). These pins are also connected to the TX and RX LED's, in which you can see them blink as you upload new code to the board!

Pin 13 you can use however, it has a special side affect of turning on the LED labeled “L” right below it.

There are even more special ports! Ports 3,5,6,9,10, and 11 are what we call PWM ports, which use Pulse Width Modulation. This Pulse Width Modulation enables the port to act like a “heartbeat” if asked to do so. Using pulses that refresh faster than the speed of your monitor, it can control the brightness of an LED (among other things) to brighten or dim at a precise percentage. I will be explaining how to use this later on when we actually need to use this.

All the rest can be set to on or off as well as to read if the port is on or off. But be careful, every port only has an output power of 40 mA!

On the right we have Power LED, Reset Button, and our Microcontroller! The Power LED is merely a status light that notifies the user if the board is functioning adequately and has power. If this board is provided power and the light it not on, unplug immediately! If the power source is too low, charge the battery, if the power source is fine, the board is drawing too much current.

The reset button resets the board, simple enough. If you hold down the reset button, it stays off until it is released.

And the Microcontroller! This beauty is the brains of this whole beast. Everything passes through this one little chip. If it fries, its not cheap, but it can be replaced. The processor speed is combined with the name of the chip. The chip is named AVR ATMEGA###-****... AVR is the company that makes these chipsets, ATMEGA is the type of architecture the chipset uses. The first two ##'s is the speed in MHz, the last # is the bit architecture. The ****'s are more information that neither of us need to remember.

On the bottom, we have the Power Pins and the Analog Input Pins. The power pins have:

RESET | 3V3 | 5V | GND | GND | VIN

The power pins are as follows:

  • VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

  • 5V. The regulated power supply used to power the microcontroller and other components on the board. This can come either from VIN via an on-board regulator, or be supplied by USB or another regulated 5V supply.

  • 3V3. A 3.3 volt supply generated by the on-board FTDI chip. Maximum current draw is 50 mA.

  • GND. Ground pins. (All are wired up to each other)

You also have 6 ports of analog inputs for what ever you like, but they can only read. (even though there is a function for analogWrite, it is for digital... Weird huh?)

The board is also described in more detail here: http://www.arduino.cc/en/Main/ArduinoBoardDiecimila

and for the mega