Sprinkler3 irrigation controller

I wanted a sprinkler controller that works with Home Assistant but doesn’t depend on it. Schedules live on the device, time comes from a battery-backed RTC, and a 20×4 LCD with four buttons covers everyday use. If Wi-Fi or Home Assistant goes down, the lawn still gets watered on time.

menu → water now → one zone → 12 min → ok, then stop clears the queue (2.5x speed)

hardware

Board: ESP32 16-relay board (ESP32_Relay_X16 V1.2), relays driven through two chained 74HC595 shift registers
Valves: 15 zone valves, plus a master valve on relay 16
Clock: DS1307 RTC module, so the controller boots with valid time even with no network
Display: LCD 2004 with a PCF8574 I2C backpack
Input: 4-key tactile module (STOP/back, previous, next, OK). The labels engraved on the printed lid are from an earlier menu layout; it wasn’t worth a reprint just to rename them.
Rain sensor: Rain Bird WR2 wireless sensor. It’s wired in, but the scheduler doesn’t use it yet
Case: 3D-printed, written in OpenSCAD. It’s a remix of pbtec’s Stable and waterproof OpenSCAD case (CC BY-NC-SA). I added the LCD window and standoffs, the cutouts and bosses for the button module, and the engraved labels. Everything is parametric, so the whole front panel is a few variables.

Inside: LCD and RTC in the lid, relay board in the base — lid on top (lcd, rtc, button module), relay board below

Common wire soldered across all relays on the underside of the board — underside of the relay board: one common wire soldered across all 16 relays to simplify the field wiring

how-it-works

Runs offline. All the logic runs on the device. Sixteen schedule slots (time, days, target zone or group) are stored on the ESP32 and survive reboots. Time comes from SNTP or Home Assistant, with the RTC as fallback. It never waters when the clock is invalid.
One zone at a time. A single queue drives every valve, so pressure stays steady, and the master valve opens only while a zone is running.
Seasonal adjust and rain delay. One “water budget” multiplier (0–200%) scales every run. Rain delay skips N days.
Usable without a phone. From the front panel you can start a zone, a group or all zones, edit schedules, zone durations and groups, set the water budget and rain delay, set the clock, and check network info or run a Wi-Fi scan.
Still a smart-home device. Native Home Assistant API, a built-in web page, OTA updates, and a fallback hotspot with a captive portal.

Controller mounted on the wall next to the Rain Bird WR2 receiver — wired in on the wall, next to the rain bird wr2 receiver

software

ESPHome: a YAML config, plus a C++ header (sprinkler3_ui.h) for the front-panel menus

hardware

how-it-works

software

~/hardware-lab