Build a GPS Tracker That Works Anywhere (No App!)

Build your own GPS tracker that sends SMS alerts when anything leaves your custom safe zone! No Bluetooth. No subscriptions. Just logic + power. This project uses an Arduino Nano, SIM800L GSM module, and NEO-6M GPS module to create a standalone tracking device that works anywhere with GSM coverage.

Key Features:

Uses Arduino Nano + SIM800L + GPS
Works anywhere with GSM coverage
Sends SMS alerts when device leaves safe zone
No app required - uses standard SMS
3D-printable custom case available
Low power consumption design

What You'll Need

Arduino Nano - Main microcontroller
SIM800L GSM Module - For SMS communication
NEO-6M GPS Module - For location tracking
Jumper Wires - For connections
Power Supply - 5V power source (battery pack recommended)
SIM Card - Active SIM card with SMS capability
Resistors - 1KΩ and 2KΩ resistors for voltage divider

Wiring Diagram

Connect the components as follows:

Arduino Nano to SIM800L:

Arduino D7 → SIM800L RX (via voltage divider: 1KΩ + 2KΩ)
Arduino D8 → SIM800L TX
Arduino 5V → SIM800L VCC
Arduino GND → SIM800L GND

Arduino Nano to NEO-6M GPS:

Arduino D4 → GPS TX
Arduino D3 → GPS RX
Arduino 5V → GPS VCC
Arduino GND → GPS GND

Important: The SIM800L module operates at 3.3V logic levels, but Arduino Nano outputs 5V. Use a voltage divider (1KΩ + 2KΩ resistors) on the RX line to prevent damage to the SIM800L module.

Complete Arduino Code

Here's the complete Arduino sketch for the GPS tracker:

      
#include <SoftwareSerial.h>
#include <TinyGPS++.h>

// GPS Module connections
#define GPS_RX_PIN 4
#define GPS_TX_PIN 3

// SIM800L Module connections
#define SIM800L_RX_PIN 7
#define SIM800L_TX_PIN 8

// Create serial objects
SoftwareSerial gpsSerial(GPS_RX_PIN, GPS_TX_PIN);
SoftwareSerial sim800l(SIM800L_RX_PIN, SIM800L_TX_PIN);

// GPS object
TinyGPSPlus gps;

// Configuration
const float SAFE_ZONE_LAT = 14.5995;  // Replace with your safe zone latitude
const float SAFE_ZONE_LON = 120.9842; // Replace with your safe zone longitude
const float SAFE_ZONE_RADIUS = 0.001;  // Radius in degrees (approximately 100 meters)
const String PHONE_NUMBER = "+639123456789"; // Replace with your phone number

// State variables
unsigned long lastCheckTime = 0;
const unsigned long CHECK_INTERVAL = 30000; // Check every 30 seconds
bool isInSafeZone = true;
bool gpsReady = false;

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
  gpsSerial.begin(9600);
  sim800l.begin(9600);
  
  Serial.println("GPS Tracker Initializing...");
  
  // Wait for SIM800L to be ready
  delay(2000);
  
  // Initialize SIM800L
  sim800l.println("AT");
  delay(1000);
  sim800l.println("AT+CMGF=1"); // Set SMS mode to text
  delay(1000);
  sim800l.println("AT+CNMI=2,2,0,0,0"); // Set SMS notification
  delay(1000);
  
  Serial.println("GPS Tracker Ready!");
  sendSMS("GPS Tracker initialized and ready.");
}

void loop() {
  // Read GPS data
  while (gpsSerial.available() > 0) {
    if (gps.encode(gpsSerial.read())) {
      if (gps.location.isValid()) {
        gpsReady = true;
      }
    }
  }
  
  // Check location every CHECK_INTERVAL
  if (millis() - lastCheckTime > CHECK_INTERVAL) {
    lastCheckTime = millis();
    
    if (gpsReady && gps.location.isValid()) {
      float currentLat = gps.location.lat();
      float currentLon = gps.location.lng();
      
      // Calculate distance from safe zone
      float distance = calculateDistance(
        SAFE_ZONE_LAT, SAFE_ZONE_LON,
        currentLat, currentLon
      );
      
      // Check if device is in safe zone
      bool currentlyInSafeZone = (distance <= SAFE_ZONE_RADIUS);
      
      // Send alert if device left safe zone
      if (isInSafeZone && !currentlyInSafeZone) {
        String message = "ALERT: Device left safe zone!\n";
        message += "Location: ";
        message += String(currentLat, 6);
        message += ", ";
        message += String(currentLon, 6);
        message += "\n";
        message += "Distance: ";
        message += String(distance * 111000, 2); // Convert to meters
        message += " meters";
        
        sendSMS(message);
        isInSafeZone = false;
      }
      
      // Update status when back in safe zone
      if (!isInSafeZone && currentlyInSafeZone) {
        sendSMS("Device returned to safe zone.");
        isInSafeZone = true;
      }
      
      // Debug output
      Serial.print("Lat: ");
      Serial.print(currentLat, 6);
      Serial.print(", Lon: ");
      Serial.print(currentLon, 6);
      Serial.print(", Distance: ");
      Serial.print(distance * 111000, 2);
      Serial.println(" meters");
    } else {
      Serial.println("Waiting for GPS signal...");
    }
  }
  
  // Handle incoming SMS
  if (sim800l.available()) {
    String response = sim800l.readString();
    Serial.println("SIM800L: " + response);
    
    // Check for location request SMS
    if (response.indexOf("LOCATION") != -1 || response.indexOf("location") != -1) {
      if (gpsReady && gps.location.isValid()) {
        String locationMsg = "Current Location:\n";
        locationMsg += "Lat: ";
        locationMsg += String(gps.location.lat(), 6);
        locationMsg += "\nLon: ";
        locationMsg += String(gps.location.lng(), 6);
        locationMsg += "\n";
        locationMsg += "https://www.google.com/maps?q=";
        locationMsg += String(gps.location.lat(), 6);
        locationMsg += ",";
        locationMsg += String(gps.location.lng(), 6);
        
        sendSMS(locationMsg);
      } else {
        sendSMS("GPS signal not available. Please wait...");
      }
    }
  }
}

// Function to calculate distance between two coordinates
float calculateDistance(float lat1, float lon1, float lat2, float lon2) {
  float dLat = (lat2 - lat1) * PI / 180.0;
  float dLon = (lon2 - lon1) * PI / 180.0;
  
  float a = sin(dLat / 2) * sin(dLat / 2) +
            cos(lat1 * PI / 180.0) * cos(lat2 * PI / 180.0) *
            sin(dLon / 2) * sin(dLon / 2);
  
  float c = 2 * atan2(sqrt(a), sqrt(1 - a));
  float distance = c; // Distance in degrees
  
  return distance;
}

// Function to send SMS
void sendSMS(String message) {
  sim800l.println("AT+CMGS="" + PHONE_NUMBER + """);
  delay(1000);
  sim800l.print(message);
  delay(100);
  sim800l.write(26); // Ctrl+Z to send
  delay(1000);
  
  Serial.println("SMS sent: " + message);
}

Configuration Steps

Install Required Libraries:

Arduino IDE → Sketch → Include Library → Manage Libraries
Search and install: "TinyGPS++"

Update Configuration:
- Set your safe zone coordinates (SAFE_ZONE_LAT, SAFE_ZONE_LON)
- Adjust safe zone radius (SAFE_ZONE_RADIUS)
- Enter your phone number (PHONE_NUMBER) with country code
Insert SIM Card:
- Use an active SIM card with SMS capability
- Ensure the SIM card has sufficient balance
- Remove PIN lock if enabled
Power Supply:
- Use a 5V power supply (battery pack recommended for portability)
- Ensure sufficient current capacity (at least 2A for SIM800L)
- SIM800L can draw up to 2A during transmission

How It Works

1. GPS Tracking: The NEO-6M GPS module continuously receives satellite signals and provides location coordinates (latitude and longitude).

2. Safe Zone Monitoring: The Arduino calculates the distance between the current location and the predefined safe zone center. If the distance exceeds the safe zone radius, an alert is triggered.

3. SMS Alerts: When the device leaves the safe zone, the SIM800L module sends an SMS alert to your phone number with the current location coordinates and distance from the safe zone.

4. Location Requests: You can send an SMS with "LOCATION" to the tracker's SIM card number, and it will reply with the current GPS coordinates and a Google Maps link.

Advanced Features

Here are some additional code snippets you can add to enhance the tracker:

1. Battery Level Monitoring

      
// Add to setup()
pinMode(A0, INPUT);

// Add function to check battery
int getBatteryLevel() {
  int sensorValue = analogRead(A0);
  int batteryPercent = map(sensorValue, 0, 1023, 0, 100);
  return batteryPercent;
}

// Call in loop() when battery is low
if (getBatteryLevel() < 20) {
  sendSMS("Low battery warning: " + String(getBatteryLevel()) + "%");
}

2. Periodic Location Updates

      
// Add to configuration
const unsigned long LOCATION_UPDATE_INTERVAL = 300000; // 5 minutes
unsigned long lastLocationUpdate = 0;

// Add to loop()
if (millis() - lastLocationUpdate > LOCATION_UPDATE_INTERVAL) {
  if (gpsReady && gps.location.isValid()) {
    String updateMsg = "Location Update:\n";
    updateMsg += "Lat: " + String(gps.location.lat(), 6);
    updateMsg += "\nLon: " + String(gps.location.lng(), 6);
    sendSMS(updateMsg);
    lastLocationUpdate = millis();
  }
}

3. Speed Monitoring

      
// Add to loop() after GPS reading
if (gps.speed.isValid()) {
  float speedKmh = gps.speed.kmph();
  
  // Alert if speed exceeds limit
  if (speedKmh > 80) { // 80 km/h limit
    String speedAlert = "Speed Alert: ";
    speedAlert += String(speedKmh, 1);
    speedAlert += " km/h";
    sendSMS(speedAlert);
  }
}

Troubleshooting

GPS not getting signal: Ensure the GPS module has a clear view of the sky. It may take several minutes to get a fix on first use.
SIM800L not responding: Check power supply (needs 2A), verify SIM card is inserted correctly, and ensure proper voltage divider on RX line.
SMS not sending: Verify SIM card has balance, check phone number format (include country code), and ensure network coverage.
Incorrect location: Wait for GPS to get a fix (LED on GPS module will blink when searching, steady when fixed).
Arduino resets: Power supply may be insufficient. Use a dedicated 5V 2A+ power supply.

3D-Printable Case

A custom 3D-printable case is available for this project. The case design includes:

Proper mounting holes for all components
Antenna access for GPS and GSM modules
Battery compartment
Ventilation for heat dissipation
Water-resistant design options

Project Tips:

Test the GPS module outdoors first to ensure it gets a signal
Use a power bank for portable operation
Consider adding a small OLED display for status information
Add a power switch to conserve battery when not in use
Use a waterproof enclosure if deploying outdoors

Safety and Legal Considerations

Important: Before deploying this tracker:

Ensure you have permission to track the item/person
Check local laws regarding GPS tracking devices
Respect privacy laws and regulations
Use responsibly and ethically

This GPS tracker project provides a solid foundation for location tracking applications. You can extend it with additional features like data logging, web dashboard integration, or multiple safe zones.

#include <SoftwareSerial.h> #include <TinyGPS++.h> // GPS Module connections #define GPS_RX_PIN 4 #define GPS_TX_PIN 3 // SIM800L Module connections #define SIM800L_RX_PIN 7 #define SIM800L_TX_PIN 8 // Create serial objects SoftwareSerial gpsSerial(GPS_RX_PIN, GPS_TX_PIN); SoftwareSerial sim800l(SIM800L_RX_PIN, SIM800L_TX_PIN); // GPS object TinyGPSPlus gps; // Configuration const float SAFE_ZONE_LAT = 14.5995; // Replace with your safe zone latitude const float SAFE_ZONE_LON = 120.9842; // Replace with your safe zone longitude const float SAFE_ZONE_RADIUS = 0.001; // Radius in degrees (approximately 100 meters) const String PHONE_NUMBER = "+639123456789"; // Replace with your phone number // State variables unsigned long lastCheckTime = 0; const unsigned long CHECK_INTERVAL = 30000; // Check every 30 seconds bool isInSafeZone = true; bool gpsReady = false; void setup() { // Initialize serial communication Serial.begin(9600); gpsSerial.begin(9600); sim800l.begin(9600); Serial.println("GPS Tracker Initializing..."); // Wait for SIM800L to be ready delay(2000); // Initialize SIM800L sim800l.println("AT"); delay(1000); sim800l.println("AT+CMGF=1"); // Set SMS mode to text delay(1000); sim800l.println("AT+CNMI=2,2,0,0,0"); // Set SMS notification delay(1000); Serial.println("GPS Tracker Ready!"); sendSMS("GPS Tracker initialized and ready."); } void loop() { // Read GPS data while (gpsSerial.available() > 0) { if (gps.encode(gpsSerial.read())) { if (gps.location.isValid()) { gpsReady = true; } } } // Check location every CHECK_INTERVAL if (millis() - lastCheckTime > CHECK_INTERVAL) { lastCheckTime = millis(); if (gpsReady && gps.location.isValid()) { float currentLat = gps.location.lat(); float currentLon = gps.location.lng(); // Calculate distance from safe zone float distance = calculateDistance( SAFE_ZONE_LAT, SAFE_ZONE_LON, currentLat, currentLon ); // Check if device is in safe zone bool currentlyInSafeZone = (distance <= SAFE_ZONE_RADIUS); // Send alert if device left safe zone if (isInSafeZone && !currentlyInSafeZone) { String message = "ALERT: Device left safe zone!\n"; message += "Location: "; message += String(currentLat, 6); message += ", "; message += String(currentLon, 6); message += "\n"; message += "Distance: "; message += String(distance * 111000, 2); // Convert to meters message += " meters"; sendSMS(message); isInSafeZone = false; } // Update status when back in safe zone if (!isInSafeZone && currentlyInSafeZone) { sendSMS("Device returned to safe zone."); isInSafeZone = true; } // Debug output Serial.print("Lat: "); Serial.print(currentLat, 6); Serial.print(", Lon: "); Serial.print(currentLon, 6); Serial.print(", Distance: "); Serial.print(distance * 111000, 2); Serial.println(" meters"); } else { Serial.println("Waiting for GPS signal..."); } } // Handle incoming SMS if (sim800l.available()) { String response = sim800l.readString(); Serial.println("SIM800L: " + response); // Check for location request SMS if (response.indexOf("LOCATION") != -1 || response.indexOf("location") != -1) { if (gpsReady && gps.location.isValid()) { String locationMsg = "Current Location:\n"; locationMsg += "Lat: "; locationMsg += String(gps.location.lat(), 6); locationMsg += "\nLon: "; locationMsg += String(gps.location.lng(), 6); locationMsg += "\n"; locationMsg += "https://www.google.com/maps?q="; locationMsg += String(gps.location.lat(), 6); locationMsg += ","; locationMsg += String(gps.location.lng(), 6); sendSMS(locationMsg); } else { sendSMS("GPS signal not available. Please wait..."); } } } } // Function to calculate distance between two coordinates float calculateDistance(float lat1, float lon1, float lat2, float lon2) { float dLat = (lat2 - lat1) * PI / 180.0; float dLon = (lon2 - lon1) * PI / 180.0; float a = sin(dLat / 2) * sin(dLat / 2) + cos(lat1 * PI / 180.0) * cos(lat2 * PI / 180.0) * sin(dLon / 2) * sin(dLon / 2); float c = 2 * atan2(sqrt(a), sqrt(1 - a)); float distance = c; // Distance in degrees return distance; } // Function to send SMS void sendSMS(String message) { sim800l.println("AT+CMGS="" + PHONE_NUMBER + """); delay(1000); sim800l.print(message); delay(100); sim800l.write(26); // Ctrl+Z to send delay(1000); Serial.println("SMS sent: " + message); }

// Add to setup() pinMode(A0, INPUT); // Add function to check battery int getBatteryLevel() { int sensorValue = analogRead(A0); int batteryPercent = map(sensorValue, 0, 1023, 0, 100); return batteryPercent; } // Call in loop() when battery is low if (getBatteryLevel() < 20) { sendSMS("Low battery warning: " + String(getBatteryLevel()) + "%"); }

// Add to configuration const unsigned long LOCATION_UPDATE_INTERVAL = 300000; // 5 minutes unsigned long lastLocationUpdate = 0; // Add to loop() if (millis() - lastLocationUpdate > LOCATION_UPDATE_INTERVAL) { if (gpsReady && gps.location.isValid()) { String updateMsg = "Location Update:\n"; updateMsg += "Lat: " + String(gps.location.lat(), 6); updateMsg += "\nLon: " + String(gps.location.lng(), 6); sendSMS(updateMsg); lastLocationUpdate = millis(); } }

// Add to loop() after GPS reading if (gps.speed.isValid()) { float speedKmh = gps.speed.kmph(); // Alert if speed exceeds limit if (speedKmh > 80) { // 80 km/h limit String speedAlert = "Speed Alert: "; speedAlert += String(speedKmh, 1); speedAlert += " km/h"; sendSMS(speedAlert); } }

Share this Source Code

Share This Article

Key Features:

What You'll Need

Wiring Diagram

Arduino Nano to SIM800L:

Arduino Nano to NEO-6M GPS:

Complete Arduino Code

Configuration Steps

How It Works

Advanced Features

1. Battery Level Monitoring

2. Periodic Location Updates

3. Speed Monitoring

Troubleshooting

3D-Printable Case

Project Tips:

Safety and Legal Considerations

Quick Actions

Technologies

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Share this Source Code

Share This Article

Key Features:

What You'll Need

Wiring Diagram

Arduino Nano to SIM800L:

Arduino Nano to NEO-6M GPS:

Complete Arduino Code

Configuration Steps

How It Works

Advanced Features

1. Battery Level Monitoring

2. Periodic Location Updates

3. Speed Monitoring

Troubleshooting

3D-Printable Case

Project Tips:

Safety and Legal Considerations

Quick Actions

Technologies

Featured Products

Bonavita Coffee 8 in 1 ( Buy 5 boxes + 1 box FREE)

Ambi Pur Car Freshener Sky Breeze Value Pack Lavender Comfort Value Pack 2.2ml Car Vent Clip (Long-lasting Car Freshener, Air Freshener)

URU4500 Digital Persona Biometric Reader Fingerprint U.are.U 4500 Fingerprint Scanner With Free SDK

ANSEN Webcam for PC Laptop Online Class 2K 1080P HD USB Web Camera with Mic

TOPICAL HAIR GROWER TRINOXTERIDE20 (ROLL ON)

NB North Bayou DUAL Monitor Arm Mount Stand F160 by NeatPH

Logitech Gaming Mouse G102 LIGHTSYNC 8,000 DPI Customizable RGB Lighting 6 Programmable Button Wired

Under Table Storage basket Cable Management Tray Desk Socket Holder Wire Organizer Rack Storage Rack

NESTEA Cleanse Lemon Cucumber Powdered Green Tea with Fiber 8.5g x 10