8. Rain Alert

Average an analog rain-plate signal, classify three states, and count transitions into the rain state.

Level: Intermediate · Time: 40 minutes

Parts and wiring

ESP32 and a 3.3 V-compatible analog rain sensor

Connect VCC→3V3, GND→GND, and AO→GPIO 34. Exposed copper plates corrode when left wet; use this module for short tests or choose an outdoor-rated sensor.

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 RAIN_PIN = 34;
const int DRY_LIMIT = 3200;  // Calibrate
const int WET_LIMIT = 2200;
 
PxServ client(PXSERV_API_KEY);
String previousState = "";
unsigned long eventCount = 0;
 
void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  PxServ::connectWifi(WIFI_SSID, WIFI_PASSWORD);
}
 
void loop() {
  long total = 0;
  for (int i = 0; i < 20; i++) {
    total += analogRead(RAIN_PIN);
    delay(10);
  }
  int raw = total / 20;
  String state = raw > DRY_LIMIT ? "dry" :
                 raw > WET_LIMIT ? "damp" : "rain";
 
  client.setData("rain/raw", String(raw));
  client.setData("rain/status", state);
  if (state != previousState) {
    if (state == "rain") eventCount++;
    client.setData("rain/event-count", String(eventCount));
    previousState = state;
  }
  delay(10000);
}

Calibration

Record dry, lightly damp, and wet values and place the two thresholds between those ranges. Reverse the comparisons if your module’s reading rises with moisture.