Redson Dev · Idea
Solar-Powered Cattle Tracker with GPS and SMS Alerts
Published June 17, 2026
Cattle rustling is a significant challenge for livestock farmers in Zimbabwe. This project describes building a low-cost, solar-powered GPS tracker that sends location updates and geofence breach alerts via SMS. A communal farmer in Matabeleland North could use this device to monitor their herd's location, enhancing security and allowing for quicker recovery of lost or stolen animals.
What you'll need
- ESP32-CAM module x1
- Neo-6M GPS module x1
- SIM800L GSM module x1
- 0.5W 5V Solar panel x1
- TP4056 Lipo charging module x1
- 3.7V 18650 Li-ion battery x1
- Plastic enclosure (weatherproof) x1
- Jumper wires, breadboard (for prototyping)
Step-by-step
- 01
Assemble the Core Modules
Connect the Neo-6M GPS module's VCC to 3.3V on the ESP32-CAM, GND to GND, TX to ESP32-CAM GPIO16 (RX2), and RX to ESP32-CAM GPIO17 (TX2). Connect the SIM800L GSM module's VCC to a stable 3.7-4.2V power source (e.g., the LiPo battery output), GND to GND, RX to ESP32-CAM GPIO18, and TX to ESP32-CAM GPIO19. Ensure the SIM800L has an active SIM card inserted.
- 02
Integrate Power Management
Connect the solar panel's positive output to the IN+ terminal of the TP4056 charging module and the negative output to IN-. Connect the 18650 Li-ion battery to the B+ and B- terminals of the TP4056. The OUT+ and OUT- terminals of the TP4056 will provide regulated power to the ESP32-CAM via its 5V pin (if using USB power) or 3.3V pin (with an appropriate step-down if directly from battery) and directly to the SIM800L.
- 03
Program the ESP32-CAM
Using the Arduino IDE with ESP32 board support, upload a sketch that initializes the GPS module via Serial2. Configure the SIM800L to send SMS messages using AT commands. The code should read GPS data, format it into a Google Maps link, and send it via SMS at timed intervals (e.g., every hour) or upon a geofence breach detected by comparing current coordinates with predefined ones. Use `TinyGPS++` library for GPS data parsing.
- 04
Implement Geofencing Logic (Optional but Recommended)
Within your ESP32 sketch, define a 'safe zone' as a set of GPS coordinates and a radius (e.g., the farm's pasture). Continuously compare the current reported GPS location against this zone. If the cattle move outside the defined perimeter, trigger an immediate SMS alert to a pre-programmed phone number with the current location, indicating a potential breach.
- 05
Enclose and Deploy
Mount all components securely within the weatherproof plastic enclosure. Ensure the solar panel is exposed to sunlight for charging and the GPS antenna has a clear sky view. Attach the device to a sturdy collar or harness for the cattle. Test the system thoroughly in a small, controlled area before full deployment in the field.
Tips
- Optimize power consumption by putting ESP32 to deep sleep between GPS fixes and SMS transmissions.
- Use a local mobile network provider that offers affordable SMS bundles for frequent alerts.