Arduino Internal Pull-Up Resistor Not Working

In this tutorial, you'll learn about Arduino Internal Pull. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

The internal pull-up resistor does not pull the pin HIGH as expected.

Quick Fix

Wrong

pinMode(5, INPUT);  // No pull-up enabled

Pin 5 floats — readings are unstable.

Right

pinMode(5, INPUT_PULLUP);  // Enable 20k pull-up
int val = digitalRead(5);
Serial.println(val);  // Prints 1 when floating

1 (HIGH) when nothing is connected to pin 5.

Prevention

Always use INPUT_PULLUP instead of INPUT for switches and buttons connected to GND. Internal pull-ups are 20-50 kOhm on AVR, ~45 kOhm on ESP32. For stronger pull, use an external resistor (10 kOhm recommended).

DodaTech engineers apply these same patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro for production IoT reliability.

FAQ