Jamie Matthews' 3D-Printed Telegram Trail Camera Snaps Critters at a Very Low Cost

Maker Jamie Matthews has written a guide to building a semisolar-powered trail camera with doppler radar sensing for a fraction of the cost of a commercial equivalent, and with automatic alerts through the Telegram messaging system.

"[This is a] Telegram enabled critter cam using the ridiculously cheap [Espressif] ESP32-CAM board and a [Handson Technology] RCWL-0516 doppler radar sensor that will connect to your home WiFi network and send through photos of any movement in your yard straight to your Telegram account," Matthews explains of the project. "With this setup you don't have to struggle with SD Cards like most of the trail cameras available plus you can instantly see any movement in your yard from anywhere in the world and you can even share the Telegram link to friends and family."

The heart of the build is an Espressif ESP32-CAM module, which includes both the ESP32 microcontroller and a low-resolution camera sensor, plus the doppler radar sensor to act as a motion detection trigger. There's an 18650-format lithium-ion battery for energy storage, with a 5V solar panel to charge it up — and while Matthews' claim of a $10 bill of materials doesn't quite hold up unless you're buying in serious bulk, it's certainly not a project that'll break the bank.

The hardware is housed in custom enclosure 3D printed in four parts: the main body, a rear cover, a separate battery cover, and a shield designed to prevent the sun from rendering the camera sensor useless. "I printed these using SBS," Matthews explains, "which is a derivative of ABS with a more rubbery property and works wonderful for rugged parts." Software running on the ESP32, meanwhile, waits for motion to trigger the doppler radar then snaps a picture — transmitting it to a Telegram channel over the module's integrated Wi-Fi connectivity.

"When starting this project I never intended the camera to be left outside unattended for multiple days, so I designed it to be powered from a single removable 18650 and a quality name brand cell easily provides us with 24 hours of working time," Matthews explains of the device's somewhat weedy solar panel.

"But just so that we don't deplete the cell every time and as such increase our battery's lifecycles I decided to add a inexpensive small 5V solar cell in parallel with the battery. If you prefer you can use a battery with a built in protection circuit, but as the solar cell is only there to assist and is too weak to ever really charge the battery it shouldn't be necessary."

A full guide to building your own trail cam, including 3D print files and source code, is available on Matthews' Instructables page.