ESP32 smart lamp switch

A button toggles a relay — the core of every smart switch.

Open in Circuit Lab Simulator

Interactive Simulation

ESP32: button toggles a relayesp32-devkit-v1

Open in Lab

Required Components Checklist

Assembly Steps

Relay module

VCC to VIN (5 V from USB), GND to GND, IN to GPIO26. Many modules accept a 3.3 V signal; check yours.

Button

Between GPIO4 and GND with INPUT_PULLUP.

Toggle on edges

Flip the state only when the button changes from HIGH to LOW.

Arduino Sketch

const int BUTTON = 4;
const int RELAY = 26;
bool on = false;
bool last = HIGH;

void setup() {
  pinMode(BUTTON, INPUT_PULLUP);
  pinMode(RELAY, OUTPUT);
  Serial.begin(115200);
}

void loop() {
  bool now = digitalRead(BUTTON);
  if (last == HIGH && now == LOW) { // falling edge = a new press
    on = !on;
    digitalWrite(RELAY, on ? HIGH : LOW);
    Serial.println(on ? "Lamp ON" : "Lamp OFF");
    delay(50); // simple debounce
  }
  last = now;
}

Challenges & Extensions

Ready to take this project further? Try these challenges:

•Add an auto-off timer.
•Remember the state across resets with Preferences (real board).
•Control it from a web page (see the Connected ESP32 course).