Practical case: ESP32 Washing Machine Monitor

#include <Arduino.h>
#include <WiFi.h>
#include <HTTPClient.h>

// ---------------------------------------------------------
// Configuration: WiFi & Webhook
// ---------------------------------------------------------
const char* WIFI_SSID = "YOUR_WIFI_SSID";
const char* WIFI_PASSWORD = "YOUR_WIFI_PASSWORD";

// For demonstration, we use httpbin.org to echo the GET request.
// In a real application, replace this with an IFTTT Webhook, 
// Home Assistant endpoint, or custom API URL.
const char* WEBHOOK_URL = "http://httpbin.org/get?laundry=finished";

// ---------------------------------------------------------
// Configuration: Hardware Pins
// ---------------------------------------------------------
const int SW420_PIN = 13;
const int BUZZER_PIN = 14;
const int LED_PIN = 27;

// ---------------------------------------------------------
// Configuration: Timing & State Machine
// ---------------------------------------------------------
// Time required without vibration to consider the cycle "finished".
// Set to 15 seconds (15000ms) for testing. 
// For real laundry machines, use 180000ms (3 minutes) or more.
const unsigned long CYCLE_TIMEOUT_MS = 15000; 

enum MachineState {
    STATE_IDLE,
    STATE_RUNNING,
    STATE_FINISHED
};

MachineState currentState = STATE_IDLE;
unsigned long lastVibrationTime = 0;
unsigned long lastAlertToggleTime = 0;
bool alertToggleState = false;

// Function prototypes
void connectToWiFi();
void sendWiFiAlert();
void handleAlertHardware();

void setup() {
    Serial.begin(115200);
    delay(1000);
    Serial.println("\n--- Laundry Vibration WiFi Alert ---");

    // Initialize pins
    pinMode(SW420_PIN, INPUT);
    pinMode(BUZZER_PIN, OUTPUT);
    pinMode(LED_PIN, OUTPUT);

    // Ensure outputs are off initially
    digitalWrite(BUZZER_PIN, LOW);
    digitalWrite(LED_PIN, LOW);

    connectToWiFi();

    Serial.println("System initialized. Waiting for vibration...");
}

void loop() {
    unsigned long currentMillis = millis();
    int vibrationDetected = digitalRead(SW420_PIN);

    // 1. Read Sensor & Update Timers
    if (vibrationDetected == HIGH) {
        lastVibrationTime = currentMillis;

        // If we were idle or already finished, a new vibration means a cycle is starting/restarting
        if (currentState == STATE_IDLE || currentState == STATE_FINISHED) {
            currentState = STATE_RUNNING;
            Serial.println("STATUS: Machine is now RUNNING.");
            // Ensure alert hardware is turned off when returning to running
            digitalWrite(BUZZER_PIN, LOW);
            digitalWrite(LED_PIN, HIGH); // Solid LED indicates running
        }
    }

    // 2. Evaluate State Machine
    if (currentState == STATE_RUNNING) {
        // Check if the timeout has elapsed since the last detected vibration
        if (currentMillis - lastVibrationTime > CYCLE_TIMEOUT_MS) {
            currentState = STATE_FINISHED;
            Serial.println("STATUS: Cycle FINISHED! Triggering alerts.");
            digitalWrite(LED_PIN, LOW); // Turn off solid LED
            sendWiFiAlert();
        }
    }

    // 3. Handle Hardware Outputs based on State
    if (currentState == STATE_FINISHED) {
        handleAlertHardware();
    } else if (currentState == STATE_IDLE) {
        // Optional: Pulse LED slowly to show system is alive but idle
        digitalWrite(LED_PIN, (currentMillis / 1000) % 2 == 0);
    }

    // Small delay to prevent tight-loop debouncing issues
    delay(50);
}

// ---------------------------------------------------------
// Helper Functions
// ---------------------------------------------------------

void connectToWiFi() {
    Serial.print("Connecting to WiFi: ");
    Serial.println(WIFI_SSID);

    WiFi.mode(WIFI_STA);
    WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

    int attempts = 0;
    while (WiFi.status() != WL_CONNECTED && attempts < 20) {
        delay(500);
        Serial.print(".");
        attempts++;
    }

    if (WiFi.status() == WL_CONNECTED) {
        Serial.println("\nWiFi connected.");
        Serial.print("IP Address: ");
        Serial.println(WiFi.localIP());
    } else {
        Serial.println("\nFailed to connect to WiFi. Continuing offline.");
    }
}

void sendWiFiAlert() {
    if (WiFi.status() == WL_CONNECTED) {
        HTTPClient http;
        Serial.print("Sending HTTP GET to: ");
        Serial.println(WEBHOOK_URL);

        http.begin(WEBHOOK_URL);
        int httpResponseCode = http.GET();

        if (httpResponseCode > 0) {
            Serial.print("HTTP Response code: ");
            Serial.println(httpResponseCode);
        } else {
            Serial.print("Error code: ");
            Serial.println(httpResponseCode);
        }
        http.end();
    } else {
        Serial.println("WiFi disconnected. Cannot send webhook alert.");
    }
}

void handleAlertHardware() {
    // Non-blocking toggle for Buzzer and LED (beep every 500ms)
    unsigned long currentMillis = millis();
    if (currentMillis - lastAlertToggleTime >= 500) {
        lastAlertToggleTime = currentMillis;
        alertToggleState = !alertToggleState;

        digitalWrite(BUZZER_PIN, alertToggleState ? HIGH : LOW);
        digitalWrite(LED_PIN, alertToggleState ? HIGH : LOW);
    }
}