ESP8266 - Secure Your Belongings: Detect Theft and Send Email Alerts

This guide will teach you how to use an ESP8266 and a force sensor to keep your items safe. We will show you how to create a system that sends you an email alert if someone tries to steal your possessions. You will learn how to prepare the ESP8266, connect the force sensor, and set it up to send emails through Gmail. We will provide step-by-step instructions and explain how this system can be useful in real-life scenarios.

ESP8266 NodeMCU Theft detection Email Notification

Hardware Preparation

1×ESP8266 NodeMCU
1×Micro USB Cable
1×Force Sensor
1×10 kΩ resistor
1×Jumper Wires
1×(Optional) DC Power Jack
1×(Optional) ESP8266 Screw Terminal Adapter

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
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Overview of Force Sensor and Gmail

We provide clear guides on Force Sensors and Gmail. Each tutorial includes complete instructions on setting up the hardware, how it functions, and connecting wires to ESP8266, with coding steps. For further details, follow these links.

How the theft detection system work

When you put an item on the force sensor, it measures the weight. The ESP8266 device records this weight. If the item is taken away, the weight is different. The ESP8266 detects this different weight and sends you an email to let you know that your item has been moved.

Wiring Diagram between Force Sensor and ESP8266

The wiring diagram between ESP8266 NodeMCU and Force Sensor

This image is created using Fritzing. Click to enlarge image

See more in ESP8266's pinout and how to supply power to the ESP8266 and other components.

ESP8266 Code

/* * This ESP8266 NodeMCU code was developed by * * This ESP8266 NodeMCU code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #include <ESP8266WiFi.h> #include <ESP_Mail_Client.h> #define WIFI_SSID "YOUR_WIFI_SSID" // CHANGE IT #define WIFI_PASSWORD "YOUR_WIFI_PASSWORD" // CHANGE IT // the sender email credentials #define SENDER_EMAIL "" // CHANGE IT #define SENDER_PASSWORD "xxxx xxxx xxxx xxxx" // CHANGE IT to your Google App password #define RECIPIENT_EMAIL "" // CHANGE IT #define SMTP_HOST "" #define SMTP_PORT 587 #define FORCE_SENSOR_PIN A0 // ESP8266 pin A0 connected to the FSR with 10K pull-down resistor #define THRESHOLD 100 // may need to callibrate this value SMTPSession smtp; void setup() { Serial.begin(9600); WiFi.begin(WIFI_SSID, WIFI_PASSWORD); Serial.print("Connecting to Wi-Fi"); while (WiFi.status() != WL_CONNECTED) { Serial.print("."); delay(300); } Serial.println(); Serial.print("Connected with IP: "); Serial.println(WiFi.localIP()); Serial.println(); pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set ESP8266 pin to input pull-up mode door_state = digitalRead(DOOR_SENSOR_PIN); // read state } void loop() { int forceValue = analogRead(FORCE_SENSOR_PIN); if (forceValue < THRESHOLD) { Serial.println("Alert! Someone has stolen your stuff!"); String subject = "Email Notification from ESP8266"; String textMsg = "This is an email sent from ESP8266.\n"; textMsg += "Alert! Someone has stolen your stuff!"; gmail_send(subject, textMsg); } } void gmail_send(String subject, String textMsg) { // set the network reconnection option MailClient.networkReconnect(true); smtp.debug(1); smtp.callback(smtpCallback); Session_Config config; // set the session config config.server.host_name = SMTP_HOST; config.server.port = SMTP_PORT; = SENDER_EMAIL; config.login.password = SENDER_PASSWORD; config.login.user_domain = F(""); config.time.ntp_server = F(","); config.time.gmt_offset = 3; config.time.day_light_offset = 0; // declare the message class SMTP_Message message; // set the message headers = F("ESP8266"); = SENDER_EMAIL; message.subject = subject; message.addRecipient(F("To Whom It May Concern"), RECIPIENT_EMAIL); message.text.content = textMsg; message.text.transfer_encoding = "base64"; message.text.charSet = F("utf-8"); message.priority = esp_mail_smtp_priority::esp_mail_smtp_priority_low; // set the custom message header message.addHeader(F("Message-ID: <>")); // connect to the server if (!smtp.connect(&config)) { Serial.printf("Connection error, Status Code: %d, Error Code: %d, Reason: %s\n", smtp.statusCode(), smtp.errorCode(), smtp.errorReason().c_str()); return; } if (!smtp.isLoggedIn()) { Serial.println("Not yet logged in."); } else { if (smtp.isAuthenticated()) Serial.println("Successfully logged in."); else Serial.println("Connected with no Auth."); } // start sending Email and close the session if (!MailClient.sendMail(&smtp, &message)) Serial.printf("Error, Status Code: %d, Error Code: %d, Reason: %s\n", smtp.statusCode(), smtp.errorCode(), smtp.errorReason().c_str()); } // callback function to get the Email sending status void smtpCallback(SMTP_Status status) { // print the current status Serial.println(; // print the sending result if (status.success()) { Serial.println("----------------"); Serial.printf("Email sent success: %d\n", status.completedCount()); Serial.printf("Email sent failed: %d\n", status.failedCount()); Serial.println("----------------\n"); for (size_t i = 0; i < smtp.sendingResult.size(); i++) { // get the result item SMTP_Result result = smtp.sendingResult.getItem(i); Serial.printf("Message No: %d\n", i + 1); Serial.printf("Status: %s\n", result.completed ? "success" : "failed"); Serial.printf("Date/Time: %s\n", MailClient.Time.getDateTimeString(result.timestamp, "%B %d, %Y %H:%M:%S").c_str()); Serial.printf("Recipient: %s\n", result.recipients.c_str()); Serial.printf("Subject: %s\n", result.subject.c_str()); } Serial.println("----------------\n"); // free the memory smtp.sendingResult.clear(); } }

Detailed Instructions

To get started with ESP8266 on Arduino IDE, follow these steps:

  • Check out the how to setup environment for ESP8266 on Arduino IDE tutorial if this is your first time using ESP8266.
  • Connect your ESP8266 board to the force sensor as shown in the diagram.
  • Connect the ESP8266 board to your computer using a USB cable.
  • Place the items you want to secure on the force sensor.
  • Open Arduino IDE on your computer.
  • Choose the correct ESP8266 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
  • Click on the Library Manager icon on the left side of the Arduino IDE to open the Library Manager.
  • Search for ESP Mail Client and choose the library created by Mobizt.
  • Click the Install button to install the ESP Mail Client library.
ESP8266 NodeMCU ESP Mail Client library
  • Copy the code and open it in the Arduino IDE software.
  • Enter your WiFi name and password in the code by changing WIFI_SSID and WIFI_PASSWORD.
  • Enter the email and password of the sender in the code by changing SENDER_EMAIL and SENDER_PASSWORD.
  • Replace the recipient's email in the code by changing RECIPIENT_EMAIL. The recipient's email may be the same as the sender's email.


  • The email address of the person sending the email should be from Gmail.
  • The password for the sender should be the App password you got before.
  • The email address of the person receiving the email can be from any email service.
  • Press the Upload button in the Arduino IDE to transfer code to the ESP8266.
  • Open the Serial Monitor.
  • Take off your item from the force sensor.
  • Check the results on the Serial Monitor.
Alert! Someone has stolen your stuff! #### Email sent successfully > C: Email sent successfully ---------------- Message sent success: 1 Message sent failed: 0 ---------------- Message No: 1 Status: success Date/Time: May 27, 2024 04:42:50 Recipient: Subject: Email Notification from ESP8266 ----------------
Autoscroll Show timestamp
Clear output
9600 baud  
  • Check your email inbox. You will find an email like this:
ESP8266 NodeMCU theft detection email

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