Usman Suriono's Espressif ESP8266 System Fires Off Alerts If the Freezer Door Is Left Open
Never lose a freezer full of food again with MQTT and email-based alerts — and even a smart display, just in case.
Semiconductor engineer and hobbyist maker Usman Suriono has designed a gadget that could save you a freezer full of food — by sending out alerts when its on-board Espressif ESP8266 detects that the freezer door has been left open too long.
"This project began after noticing the basement freezer door was sometimes left ajar, and the built-in beeper wasn't loud enough to be heard upstairs," Suriono explains. "MQTT was chosen for this project due to its open-source nature, free availability, lightweight design, widespread use in the IoT community, and extensive resources. The [Espressif] ESP8266 is a tiny but mighty computer chip that's become a favorite for many electronics enthusiasts and professionals, especially those working with the Internet of Things (IoT). It has built-in Wi-Fi, making it easy to connect devices to wireless networks and the internet."
The device is simple enough: the Espressif ESP8266 microcontroller is connected to a magnetic reed switch — a pair of wires enclosed in glass that can be separated, or connected depending on which type you buy, using a nearby magnet. Said magnet lives in a 3D-printed housing on the freezer door; the reed switch next to it on the freezer body itself, connected to the Espressif ESP8622 in its own 3D-printed housing.
When the door is opened, the microcontroller springs into life — counting down from 120 seconds before firing off an MQTT event if the door hasn't been closed. A separate box upstairs has a display showing the current door status and the countdown, if one is active — while an email is also fired off to trigger an alert on the user's phone for good measure.
The project is documented in full on Suriono's Instructables page; the source code for both the door sensor and the display unit has been published to GitHub under an unspecified license. The 3D-print files, meanwhile, are available on Printables under the Creative Commons Attribution-NonCommercial 4.0 International license.