Controller in DIN Rail Enclosure
(click images to enlarge)

For a cold storage room with a refrigeration unit, a free-cooling fan was added to allow outside air to cool the room whenever outside temperatures are low enough.

The controller shown here was developed to measure inside and outside temperatures, and activate the refrigeration compressor or the fan accordingly.

The first version of this controller, implemented with an ATMEGA8 MCU, had been in service for over 10 years.

The new version which uses an ESP8266 based controller module with built-in WiFi interface can additionally reports its operational status to a server based on the EmonCMS software, where data is stored for long-term tracking and graphical reporting.

The ESP8266 program is written in Lua and runs in the NodeMCU environment.

Details will follow shortly!

Display

Display (128x64 OLED)

Interior 1

Interior – Solid-state relays on left, PSU module top left, display top center.

Interior 2

Interior – ESP8266 module (red) in center.

Sample recording

Sample recording

Circuit diagram