Rushabh's Digital Garden

Arduino Uno

3 min read

The Arduino Uno is one of the most popular microcontroller boards used in electronics, prototyping, and IoT projects. Based on the ATmega328P microcontroller, it is beginner-friendly, open-source, and widely supported by a large community.

1. Overview of Arduino Uno

  • Microcontroller: ATmega328P

  • Operating Voltage: 5V

  • Input Voltage (recommended): 7-12V

  • Clock Speed: 16 MHz

  • Digital I/O Pins: 14 (of which 6 can provide PWM output)

  • Analog Input Pins: 6

  • Flash Memory: 32 KB (0.5 KB used by bootloader)

  • SRAM: 2 KB

  • EEPROM: 1 KB

2. Arduino Uno Board Layout and Parts

A. USB Port

  • Used to upload code from the computer to the board.

  • Also provides power (5V) to the board during programming/testing.

B. Power Jack (Barrel Jack)

  • Allows powering the board using an external power supply (7–12V).

C. Voltage Regulator

  • Converts higher input voltage (from the power jack) down to 5V.

D. ATmega328P Microcontroller

  • The brain of the board. It executes the uploaded sketches (programs).

E. Digital I/O Pins (0–13)

  • Used for digital input/output operations.

  • Pins 0 (RX) and 1 (TX) are used for serial communication.

F. PWM Pins

  • Pins 3, 5, 6, 9, 10, and 11 can output PWM signals using the analogWrite() function.

G. Analog Input Pins (A0–A5)

  • Used to read analog signals (0–5V), such as from sensors.

  • Each pin has a 10-bit ADC (Analog-to-Digital Converter).

H. Power Pins

  • Vin: Input voltage to the Arduino board (when using external power).

  • 5V: Regulated 5V output (used to power sensors/modules).

  • 3.3V: 3.3V output (low-power modules).

  • GND: Ground pins (0V reference).

  • AREF: Analog Reference pin for analog inputs (optional use).

I. Reset Button

  • Resets the microcontroller, restarting the current program.

J. ICSP Header (In-Circuit Serial Programming)

  • For low-level programming of the microcontroller using an external programmer.

K. Crystal Oscillator

  • Maintains timing accuracy with a clock speed of 16 MHz.

L. TX and RX LEDs

  • Indicate data being transmitted (TX) or received (RX) via USB/serial.

M. Onboard LED (Pin 13)

  • A simple LED connected to digital pin 13 for testing.

3. Pin Description Summary

Pin TypePin NumbersFunction
Digital I/O0–13General-purpose digital input/output
PWM3, 5, 6, 9, 10, 11Digital pins with PWM capability
Analog InputA0–A5Read analog voltages (0–5V)
Power PinsVin, 5V, 3.3V, GNDPower inputs and outputs
Serial Communication0 (RX), 1 (TX)Receive/transmit serial data
SPI (via ICSP)10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK)Serial Peripheral Interface
I2CA4 (SDA), A5 (SCL)Inter-Integrated Circuit communication
ResetRESET pin/buttonResets the microcontroller

4. Arduino Programming and IDE

  • The Arduino Uno is programmed using the Arduino IDE (based on C/C++).

  • Code uploaded is called a sketch.

  • Uses simple functions:

    • setup() – runs once at startup.

    • loop() – runs repeatedly after setup.

5. Applications of Arduino Uno

  • Sensor-based projects (temperature, motion, humidity)

  • Home automation

  • Robotics

  • IoT prototypes

  • Educational learning kits

  • Motor control and automation

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