Circuits &
Arduino Basics

Code

Arduino Uno: Pin Layout

• Power: 5V 3.3V GND VIN
• Digital pins (0–13): Output HIGH (5V) or LOW (0V)
• Analog pins (A0–A5): Read variable voltages → 0 to 1023
• PWM pins (~3,5,6,9,10,11): Simulate analog output via analogWrite() (0–255)

Code

Programming an Arduino

Language: C/C++

void setup() {
  // Runs ONCE when the Arduino turns on
  // Use this to configure your pins
}

void loop() {
  // Runs FOREVER until the Arduino loses power
  // Put your main logic here
}

Code

Basic Functions

pinMode(pin, mode);// Set pin as INPUT or OUTPUT

digitalRead(pin);         // Read HIGH or LOW from a digital pin
digitalWrite(pin, value); // Write HIGH or LOW to a digital pin

analogRead(pin);          // Read 0–1023 from an analog pin (A0–A5)
analogWrite(pin, value);  // Write PWM 0–255 to a ~ pin

delay(ms);                // Pause execution for ms milliseconds

Serial.begin(baud);       // Start serial communication at baud rate
Serial.print(value);      // Print value to the serial monitor

Build

Follow Along: Fan Speed Indicator

Build a fan with a speed indicator using LEDs.

• Turn potentiometer → motor spins faster (powered directly from the pot)
• Below threshold 1: no lights
• Middle zone: Green LED on
• Above threshold 2: Red LED on

Parts: Potentiometer, fan, 2 LEDs, 2 resistors