Arduino random() Returns Same Sequence Every Run

In this tutorial, you'll learn about Arduino random() Returns Same Sequence Every Run. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

random() produces identical sequences every time the board is reset.

Quick Fix

Wrong

int r = random(100);  // Same every reset

Same sequence of numbers every power cycle.

Right

void setup() {
  Serial.begin(9600);
  // Seed from floating analog pin
  randomSeed(analogRead(A0));
}

void loop() {
  int r = random(100);
  Serial.println(r);
  delay(500);
}

Different sequence of random numbers each reset.

Prevention

Always call randomSeed() with a noise source. Do NOT use a fixed value like randomSeed(42). The best seed is analogRead() on a floating analog pin. For better randomness, XOR multiple analog readings. On ESP32, use the hardware random number generator (esp_random()).

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

FAQ