Arduino sleep modes - Mini Project: Build & Apply

Arduino Sleep Modes

📖 Scenario: You have a small Arduino project that runs on battery power. To save battery, you want the Arduino to sleep when it is not doing anything and wake up when a button is pressed.

🎯 Goal: Build a simple Arduino program that puts the board into sleep mode and wakes it up using a button press.

📋 What You'll Learn

Use the avr/sleep.h library to control sleep modes

Set up a button on pin 2 to wake the Arduino from sleep

Put the Arduino into sleep mode inside the loop()

Print a message to the Serial Monitor when the Arduino wakes up

💡 Why This Matters

🌍 Real World

Battery-powered devices like remote sensors or wearable gadgets use sleep modes to save power and extend battery life.

💼 Career

Understanding sleep modes is important for embedded systems engineers working on low-power IoT devices and hardware optimization.

1

Setup button input and Serial communication

Write code to set pin 2 as an input with an internal pull-up resistor. Also, start Serial communication at 9600 baud in the setup() function.

Arduino

void setup() {
  // Your code here
}

void loop() {
  // Your code here
}

Need a hint?

Use pinMode(2, INPUT_PULLUP); to set the button pin. Use Serial.begin(9600); to start serial communication.

2

Configure sleep mode and interrupt

Add code to set the sleep mode to SLEEP_MODE_PWR_DOWN and attach an interrupt to pin 2 that will wake the Arduino when the button is pressed.

Arduino

#include 

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  // Your code here
}

void loop() {
  // Your code here
}

Need a hint?

Use set_sleep_mode(SLEEP_MODE_PWR_DOWN); to set the sleep mode. Use attachInterrupt(digitalPinToInterrupt(2), wakeUp, LOW); to attach the interrupt.

3

Put Arduino to sleep inside loop

Inside the loop(), add code to put the Arduino to sleep using sleep_enable() and sleep_cpu(). Make sure to disable sleep after waking up.

Arduino

#include 

void wakeUp() {
  // This function will be called when interrupt occurs
}

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  attachInterrupt(digitalPinToInterrupt(2), wakeUp, LOW);
}

void loop() {
  // Add sleep code here
}

Need a hint?

Use sleep_enable(); before sleep_cpu(); and sleep_disable(); after waking up. Print messages before and after sleep.

4

Test and observe output

Upload the complete program and observe the Serial Monitor. The Arduino should print Going to sleep..., then sleep until the button on pin 2 is pressed, then print Woke up!. Write the exact output you see after pressing the button once.

Arduino

#include 

void wakeUp() {
  // This function will be called when interrupt occurs
}

void setup() {
  pinMode(2, INPUT_PULLUP);
  Serial.begin(9600);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  attachInterrupt(digitalPinToInterrupt(2), wakeUp, LOW);
}

void loop() {
  Serial.println("Going to sleep...");
  delay(100); // Give time for message to send
  sleep_enable();
  sleep_cpu();
  sleep_disable();
  Serial.println("Woke up!");
  delay(1000); // Wait before sleeping again
}

// Observe output after pressing the button once

Need a hint?

Open the Serial Monitor at 9600 baud. Press the button connected to pin 2 once. You should see the messages printed before and after sleep.