Grigorii Merkushev's Espressif ESP32-Based Terrarium Controller Keeps Corn Snakes Happy and Healthy

Corn snake pet-parent Grigorii Merkushev has turned to a custom-designed circuit board, built around an Espressif ESP32, to keep his slithering charges happy — creating a programmable terrarium controller.

"For the last two years, we got four different corn snakes," Merkushev explains. "All of them are different, different colors, characters, and sizes, but all of them like the same things. They like to be warm during the day, cool during the night, and be fed every other week. For the feeding process, there is not much to automate, but for temperature control, I found some ugly solutions. The most common solution is to have a wall plug with a timer."

Unsatisfied with such a fix, Merkushev decided to engineer something together instead: a custom controller that could keep the "hot zone" and "cool zone" within the snakes' habitat at the right temperatures. An initial prototype took the form of a Bluetooth to MQTT gateway running on a Raspberry Pi Zero single-board computer, linked to a temperature sensor and a heater control plug via Home Assistant.

"This solution was working but if sensors start to fail or something happens to the Wi-Fi plug, a snake could get overheated or get cold," says Merkushev. "It happened once and the snake got cold for a few hours so I decided to move forward and work on a standalone solution for the terrarium."

Having put together a proof-of-concept using off-the-shelf parts, Merkushev iterated through a range of designs before designing a series of circuit boards. With each successive redesign new features were added: The final version includes a switch from through-hole to surface-mount components where possible, an ESP32-WROOM-32 module, the ability to reboot sensors, three relays, a real-time clock, an I2C connection for a display, and support for up to six DHT22 temperature and humidity sensors.

"This journey was a great use of time and I had a lot of fun," Merkushev concludes, while revealing work on successive variants including a v1.7, which includes an on-board programmer and USB Type-C connectivity. "I highly encourage everyone who makes their own project to try PCB design as it is way easier than it looks."

Full details are available on Merkushev's blog post, while design files have been published to GitHub under an unspecified open-hardware license.