Sprinkler System

6-Zone WiFi Sprinkler Controller

A custom PCB for controlling up to six 24 VAC irrigation solenoid valves via WiFi, using an ESP32 and ESPHome with native Home Assistant integration.

Features

• 6 independent zones — each zone switches a 24 VAC solenoid valve via an Omron G5LE-1 relay
• WiFi control — ESP32-WROOM-32U with external U.FL antenna connector
• Home Assistant integration — ESPHome firmware; zones appear as switch entities
• Onboard power supply — HLK-PM01 AC-DC module (mains → 5 V); AMS1117-3.3 regulator (5 V → 3.3 V for ESP32)
• Relay isolation — ULN2803A Darlington array isolates ESP32 GPIOs from relay coil drive current
• Protected design — varistors on each zone output and across the mains input and transformer primary (RV1/RV2), time-delay fuses on the mains and 24 VAC supplies, per-zone RC snubbers, and an optocoupler-isolated 24 VAC rail sense

⚠️ Safety

This board carries mains voltage (Line and Neutral) on the PCB.
The HLK-PM01 module is connected directly to mains. The 24 VAC solenoid rail is transformer-isolated but still carries AC voltage.

• Do not touch or probe the board while it is powered.
• The enclosure must be non-conductive and fully closed before applying mains power.
• All mains wiring must comply with local electrical codes. Use appropriately rated cable and terminals.
• The external transformer must be safety-rated (UL, CE, or equivalent) for your locale.
• Replace fuses only with the specified ratings — see the BOM below.

See Assembly Notes for enclosure requirements and conformal coating instructions.

How It Works

The controller has three linked paths: logic power, 24 VAC valve power, and relay control.

Logic power: Mains → F1 → HLK-PM01 → 5 V → AMS1117-3.3 → 3.3 V → ESP32 + logic

24 VAC path: Mains → F1 → G3MB-202P SSR (K1, GPIO16) → J2 → external transformer → J3 → F2 → zone relays (K20–K25) → solenoids

Control: ESP32 GPIO17–23 → ULN2803A → relay coils K20–K25 → zone outputs J20–J25

When a zone is activated, the ESP32 first enables the 24 VAC rail (K1), then drives the selected relay through the ULN2803A. The ULN2803A acts as a low-side driver, keeping ESP32 GPIO current low while switching the 24 VAC solenoid load through the relay contacts.

Bill of Materials

See manufacturing/bom/bom.csv for the full BOM with quantities and footprints.

Reference

• Wiring & GPIO — connector pinouts and GPIO assignments
• ESPHome Configuration — full firmware config, fault detection, and optional pump relay setup
• Assembly Notes — step-by-step build and commissioning guide

Project Structure

Sprinkler System.kicad_pro    ← KiCad project file
Sprinkler System.kicad_sch    ← Schematic
Sprinkler System.kicad_pcb    ← PCB layout
Sprinkler System.pretty/      ← Custom footprints and 3D models
symbols/                       ← Custom symbol library (G3MB-202P)
manufacturing/
  gerbers/                     ← Gerber files for PCB fabrication
  drill/                       ← Excellon drill files
  pos/                         ← Pick-and-place centroid files
  bom/bom.csv                  ← Bill of materials
docs/
  schematic.pdf                ← Schematic PDF
  pcb.pdf                      ← PCB layer PDF
  board.step                   ← 3D STEP model
  wiring.md                    ← Connector and GPIO reference
  esphome.md                   ← ESPHome firmware configuration
  assembly.md                  ← Build and commissioning guide
.githooks/pre-commit           ← Auto-exports fabrication outputs on commit
setup / setup.ps1              ← One-time dev environment setup
release / release.ps1          ← Tag a release version

Developing

First-time setup

.\setup.ps1

Configures the git hook path and verifies kicad-cli is available. Use ./setup in Git Bash / WSL.

Fabrication exports

Gerbers, drill files, PDFs, BOM, netlist, and STEP are regenerated automatically by the pre-commit hook whenever Sprinkler System.kicad_pcb or Sprinkler System.kicad_sch are staged. No manual export step is needed.

Run DRC and ERC from within KiCad before committing — fix all errors before submitting to a board house.

Releasing

.\release.ps1 v1.1.0

Stamps the schematic and PCB title blocks with the version and date, commits (triggering a fresh fabrication export), and creates the git tag. Use ./release v1.1.0 in Git Bash / WSL. Then push:

git push && git push origin v1.1.0