Upgrading an Irrigation Controller with ESP8266, Tasmota and Home Assistant
New automation hardware leaves existing irrigation system in place.
Like many of us, the hacker in charge of “New Adventures in WiFi” has been working on home automation — in this case a smart WiFi-enabled irrigation controller for the garden. While there are a variety of ways that this can be achieved, he chose to use an ESP8266 module to interface with his existing off-the-shelf Holman irrigation system, which could already control up to six stations via 24VAC.
Instead of replacing the standard Holman controller, this self-proclaimed "smart home addict" built a parallel device that gets its power from the original hardware, and still lets it control irrigation as needed. Power had to be converted from 24VAC to 12VDC to run the new controller’s ESP8266-based (ESP-01 module) solenoid bank, first provided a rather sketchy step down regulator/bridge rectifier module. After that eventually failed, it was swapped out for a more expensive unit (~$40) meant for CCTV use. The new relays were wired into the original controller with CAT6 cable as parallel switches, allowing each to operate independently.
The ESP-01 module was flashed with Tasmota home automation firmware for control by Home Assistant via Google Calendar integration. The one hitch here is that Google Calendar only gets checked every 15 minutes — generally not a big deal, but something to keep in mind when scheduling or troubleshooting a new system. Although the author suspects its unlikely that anyone will implement a system exactly like this, perhaps it will provide inspiration for other projects!
