Smart Wireless SMS Notification System Using Seeed Studio XIAO ESP32

XIAO ESP32 C6

Ultrasonic Distance Sensor - HC-SR04

male to male jumper wires

Breadboard 100x50

Arduino IDE

<html><body><h3>🧠 Project Overview</h3>This project demonstrates how to build a Wi-Fi-connected SMS alert system with the ultra-compact Seeed Studio XIAO ESP32-S3 microcontroller. Instead of using a traditional GSM module, this design uses a free cloud SMS API to send text messages when a movement or object is detected by an HC-SR04 ultrasonic sensor. By combining inexpensive hardware with cloud connectivity and simple Arduino programming, you can create a real-time alert system for security, monitoring, and notification applications. <figure><img src="https://projects.arduinocontent.cc/8aecc3a6-3293-4bc9-90da-968128a3f578.jpg"/><figcaption>Seeed Studio Xiao ESP32</figcaption></figure><h3>What does the Project do?</h3>When the ultrasonic sensor detects an object closer than a set distance threshold (e.g., 100 cm), the XIAO ESP32 connects to Wi-Fi and sends an HTTP request to a cloud service. The cloud API then delivers a text message directly to a preconfigured phone number. This method allows SMS alerts without adding GSM hardware or SIM cards, significantly lowering cost and simplifying the design. <h3>What You’ll Build</h3><ol><li>You’ll assemble a detector that: </li><li>Measures distance with an HC-SR04 ultrasonic sensor. </li><li>Connects to your Wi-Fi network. </li><li>Sends an HTTP request to a cloud SMS API when motion is detected. </li><li>Delivers an SMS alert to your phone in real time. </li></ol><h3>📋 Key Features</h3><ol><li>Real-time SMS notifications sent via Wi-Fi using a cloud API. </li><li>Compact design using the Seeed Studio XIAO ESP32-S3 board. </li><li>Motion or proximity detection with the HC-SR04 ultrasonic sensor. </li><li>Easy setup and programming with the Arduino IDE. </li><li>Expandable: other sensors (temperature, light, buttons) can trigger SMS similarly. </li></ol><h3>📦 Components Needed</h3><ol><li>Seeed Studio XIAO ESP32-S3 microcontroller board </li><li>HC-SR04 Ultrasonic Sensor for motion detection </li><li>Breadboard and jumper wires </li><li>Wi-Fi network for internet connectivity </li><li>Free CircuitDigest Cloud SMS API account (to get API key and template ID) </li></ol><h3>🧩 Software &amp; Tools</h3>Arduino IDE Used for writing, compiling, and uploading the program to the ESP32. ESP32 Board Package Installed in Arduino IDE to support XIAO ESP32-S3 programming. Cloud SMS API A free or trial-based SMS service is used to send messages via HTTP requests. The user must configure: API Key Template ID Receiver phone number <h3>How It Works</h3><ol><li>Power &amp; Wi-Fi: The ESP32 boots and connects to your Wi-Fi network. </li><li>Distance Measurement: The HC-SR04 constantly measures the distance to the nearest object. </li><li>Trigger Check: When the measured distance is below a threshold (e.g., 100 cm), it’s considered a trigger event. </li><li>SMS API Call: The ESP32 sends an HTTP POST with an API key, template ID, and message values to the SMS service. </li><li>SMS Delivery: The cloud API forwards the formatted SMS to your mobile phone. </li></ol> <figure><img src="https://projects.arduinocontent.cc/94123b52-31d9-4e9c-9a18-fbabf78979a5.jpg"/><figcaption>Wiring diagram</figcaption></figure><h3>Wiring</h3>HC-SR04 → SEEED Studio XIAO ESP32 VCC → 5V GND → GND Trig → GPIO 5 Echo → GPIO 3 Connect only power and two signal lines — the setup remains clean and simple. <figure><img src="https://projects.arduinocontent.cc/1a3c1766-efe5-4f80-9b6e-07068be172fe.jpg"/><figcaption>Pinout</figcaption></figure><h3>Arduino Code (Essentials)</h3>Libraries <pre>#include &lt;WiFi.h&gt; </pre>Connects to Wi-Fi. Sensor Pins <code class="code">#define TRIG_PIN 5</code><code class="code">#define ECHO_PIN 3</code>Wi-Fi Credentials <pre>const char *ssid = "YourSSID"; </pre><pre>const char *password = "YourPassword"; </pre>SMS API Details <pre>const char* apiKey = "YOUR_API_KEY"; </pre><pre>const char* templateID = "103"; </pre><pre>const char* mobileNumber = "91XXXXXXXXXX"; </pre><pre>const char* var1 = "Sensor"; </pre><pre>const char* var2 = "Detected"; </pre>Send SMS Function <pre>void sendSMS() { </pre><pre>	 if (WiFi.status() == WL_CONNECTED) { </pre><pre>	 WiFiClient client; </pre><pre>	 String apiUrl = "/send_sms?ID=" + String(templateID); </pre><pre>	 if (client.connect("www.circuitdigest.cloud", 80)) { </pre><pre>	 String payload = "{\"mobiles\":\"" + String(mobileNumber) + </pre><pre>	 "\",\"var1\":\"" + String(var1) + "\",\"var2\":\"" + String(var2) + "\"}"; </pre><pre>	 client.println("POST " + apiUrl + " HTTP/1.1"); </pre><pre>	 client.println("Host: www.circuitdigest.cloud"); </pre><pre>	 client.println("Authorization: " + String(apiKey)); </pre><pre>	 client.println("Content-Type: application/json"); </pre><pre>	 client.println("Content-Length: " + String(payload.length())); </pre><pre>	 client.println(); </pre><pre>	 client.println(payload); </pre><pre>	 } </pre><pre>	 client.stop(); </pre><pre>	 } </pre><pre>} </pre>Distance Measurement <pre>float readDistance() { </pre><pre>	 digitalWrite(TRIG_PIN, LOW); </pre><pre>	 delayMicroseconds(2); </pre><pre>	 digitalWrite(TRIG_PIN, HIGH); </pre><pre>	 delayMicroseconds(10); </pre><pre>	 digitalWrite(TRIG_PIN, LOW); </pre><pre>	 long duration = pulseIn(ECHO_PIN, HIGH); </pre><pre>	 return duration * 0.034 / 2; // cm </pre><pre>} </pre><h3>Setup &amp; Loop</h3><ol><li>Connect to Wi-Fi in setup(). </li><li>Continuously read distance in loop(). </li><li>Trigger sendSMS() when an object is closer than 100 cm. </li></ol><h3>Testing &amp; Output</h3>Open the serial monitor (9600 baud) to view Wi-Fi connection status and distance values. When an object enters your set range, the SMS API request is sent and your mobile receives a text alert. <h3>Tips &amp; Troubleshooting</h3>No SMS? Verify your API key, template ID, and the phone number format (include country code). Wi-Fi Issues: Ensure your ESP32 sees your network and reconnects if dropped. <h3>Expand &amp; Improve</h3><ol><li>Replace ultrasonic with another sensor (e.g., PIR or temperature). </li><li>Send alerts to multiple numbers by formatting the mobiles list. </li><li>Add local alarms (LEDs or buzzers) for offline alerting. </li></ol> <figure><img src="https://projects.arduinocontent.cc/81ddcf6f-5520-49af-8ba1-e3013846e126.jpg"/><figcaption>hardware connenction</figcaption></figure><h3>Real-World Uses</h3><ol><li>This compact SMS alert system can power: </li><li>Home or office security alerts </li><li>Tank level monitoring </li><li>Parking occupancy notifications </li><li>Industrial safety alerts </li></ol><h3>✅ Conclusion</h3>This project demonstrates a simple yet powerful way to build an SMS alert system using Wi-Fi instead of cellular hardware. By combining the Seeed Studio XIAO ESP32 with a cloud SMS API, the system achieves reliable real-time notifications with minimal hardware cost. It is ideal for beginners learning IoT communication as well as developers looking for a lightweight alert mechanism that can be easily extended for real-world applications. <figure><img src="https://projects.arduinocontent.cc/a4394b3f-6df6-4ef3-94df-7491ffd42705.gif"/><figcaption>Working Demo</figcaption></figure> </body></html>

Smart Wireless SMS Notification System Using Seeed Studio XIAO ESP32

Build a compact IoT alert system using a SEEED Studio XIAO ESP32 and ultrasonic sensor to send SMS notifications over Wi-Fi via a cloud SMS API.