ESP32 Send Messages to WhatsApp via CallMeBot

Sends WhatsApp messages from ESP32 using free CallMeBot API. When sensor threshold exceeded (e.g., temperature > 30C from DHT22), ESP32 sends WhatsApp alert message directly to phone number. Setup: Add CallMeBot contact in WhatsApp and send 'I allow callmebot to send me messages', receive API key. ESP32 sends HTTP GET to api.callmebot.com with message, phone number, and API key. Messages sent within 2 seconds. Includes: periodic sensor reports every hour, immediate alerts on threshold breach, confirmation message on system boot, command-based replies using Telegram Bot hybrid approach. URL encoding handles special characters in messages. Rate limiting: avoid more than 1 message per second. Works for PIR motion alerts, water leak detection, power outage alerts. Libraries: WiFi, HTTPClient, DHT, ArduinoJson.

Detailed Project Description

ESP32 Send Messages to WhatsApp via CallMeBot connects an embedded device to the network so its data can be viewed and its outputs controlled from a browser, app or cloud service.

How It Works
1. The device joins the network and registers with the server/cloud (or hosts its own web page).
2. Sensor values are published and outputs are controlled through HTTP, MQTT, BLE or a cloud SDK.
3. A web/app front-end shows live values in gauges and charts and offers control buttons.
4. Data is stored for history and the firmware can be updated over the air where supported.

Key Components and Their Role
- ESP32: dual-core Wi-Fi + Bluetooth microcontroller that runs the firmware, reads the sensors and hosts the network connection.
- DHT22: digital temperature and humidity sensor with better accuracy than DHT11.
- PIR motion sensor: passive infrared sensor that detects human movement.
- Telegram Bot API: messaging channel used to send alerts and receive commands.
- WhatsApp API: messaging channel used to deliver instant alerts to a phone.

Implementation Steps
1. Collect the components and study each module's datasheet (pin-out, voltage, interface).
2. Wire the circuit on a breadboard following the pin mapping; power sensors from the correct rail (3.3 V / 5 V).
3. Install Arduino IDE, DHT Library, HTTPClient Library and the required libraries; flash a minimal test sketch for each module separately.
4. Write the main firmware: read sensors → process → drive outputs / send data.
5. Configure network or cloud credentials and test communication end-to-end.
6. Calibrate thresholds, add error handling (reconnect, sensor time-out) and run a long-duration test.
7. Finalise on a PCB / enclosure and document wiring, code and results.

Key Features
- Live data in the browser/app
- Remote control
- History storage
- Secure access

Expected Output
On completion the student will have a responsive web/app dashboard reflecting the device state in real time.

Deliverables
- Complete source code with comments
- Circuit diagram and pin mapping
- Project report with screenshots and results
- Demonstration-ready build