7. Door Status Sensor

Detect whether a door is open or closed with a magnetic reed switch. Data is published only when the state changes, reducing unnecessary network traffic.

Level: Beginner · Time: 25 minutes

Parts and wiring

ESP32 DevKit V1 and normally open reed switch with magnet

Reed-switch terminal	ESP32
First side	GPIO 18
Other side	GND

PxServ keys

Key	Values
`door/status`	`open` / `closed`
`door/change-count`	Total state transitions

Complete sketch


#include <PxServ.h>
 
const char* WIFI_SSID = "your_wifi_ssid";
const char* WIFI_PASSWORD = "your_wifi_password";
const char* PXSERV_API_KEY = "your_pxserv_api_key";
const int REED_PIN = 18;
 
PxServ client(PXSERV_API_KEY);
int previousState = -1;
unsigned long changeCount = 0;
 
void publishDoorState(int state) {
  bool doorClosed = state == LOW;
  client.setData("door/status", doorClosed ? "closed" : "open");
  client.setData("door/change-count", String(changeCount));
  Serial.println(doorClosed ? "Door closed" : "Door open");
}
 
void setup() {
  Serial.begin(115200);
  pinMode(REED_PIN, INPUT_PULLUP);
  PxServ::connectWifi(WIFI_SSID, WIFI_PASSWORD);
}
 
void loop() {
  int currentState = digitalRead(REED_PIN);
  if (currentState != previousState) {
    delay(30);
    currentState = digitalRead(REED_PIN);
    if (currentState != previousState) {
      if (previousState != -1) changeCount++;
      publishDoorState(currentState);
      previousState = currentState;
    }
  }
  delay(20);
}

Test and mounting

Move the magnet toward and away from the switch. If status is reversed, invert the doorClosed condition. Mount the sensor on the fixed frame and the magnet on the moving door, within the manufacturer’s sensing distance when closed.