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ESP32 Relay Automation

This project implements a modular relay-control subsystem for an ESP32-based indoor hydroponics automation system.

The firmware is designed with object-oriented C++ and separates relay behavior, safety rules, timers, command processing, and actuator configuration into independent components. Its purpose is to provide a reliable foundation that can later integrate sensors, schedules, automation rules, persistent configuration, Wi-Fi, and a REST API.

The current implementation controls four actuators:

• Object-oriented relay abstraction
• Centralized relay management
• Safe startup state for all outputs
• Active-low relay support
• Manual ON and OFF commands
• Timed relay activation
• Automatic timer expiration
• Manual relay locking and unlocking
• Minimum OFF-time protection
• Maximum ON-time protection
• Command validation and structured result codes
• Control-source validation
• Serial command interface
• Status reporting for relays and active timers
• Capacity prepared for up to 16 relays

The system was designed to avoid direct and uncontrolled GPIO manipulation.

Every command passes through a validation layer before reaching the physical relay. Depending on the actuator configuration, the firmware can reject commands because of:

• Disabled or uninitialized relay
• Active safety lock
• Fault state
• Invalid command source
• Invalid or excessive duration
• Required timed activation
• Minimum OFF time not yet completed
• Existing active timer
• Timer capacity limit

During startup, all registered relays are initialized and moved to their configured safe state before the serial interface becomes available.

Electrical safety: Mechanical relays may switch dangerous voltages. Use proper isolation, protection, grounding, enclosures, and qualified supervision when working with mains electricity.

flowchart TD
 UI[Serial Command Interface]
 CP[RelayCommandProcessor]
 TM[TimerManager]
 RM[RelayManager]
 R[Relay]
 AC[ActuatorCatalog]
 HW[Physical Relay / GPIO]
 UI --> CP
 CP --> RM
 CP --> TM
 TM --> CP
 AC --> R
 RM --> R
 R --> HW

RelaysControl/
├── include/
│ ├── automation/
│ │ ├── commands/
│ │ └── timers/
│ ├── core/
│ └── relays/
├── src/
│ ├── automation/
│ │ ├── commands/
│ │ └── timers/
│ ├── relays/
│ └── main.cpp
├── test/
├── platformio.ini
└── README.md

Open the serial monitor at 115200 baud.

status
on 1
on 3 10000
off 1
lock 2
unlock 2

• ESP32 DevKit V1 / ESP-WROOM-32
• Compatible relay module
• Proper external power supply for the relay board and connected loads
• Common ground where electrically appropriate
• Appropriate electrical protections

• Visual Studio Code
• PlatformIO
• Arduino Framework for ESP32

Clone the repository:

git clone https://github.com/Agus-yanez/RelaysControl.git
cd RelaysControl

Build the firmware:

pio run

Upload it to the ESP32:

pio run --target upload

Open the serial monitor:

pio device monitor

• Relay abstraction
• Centralized relay manager
• Safe startup states
• Relay locks
• Timed activations
• Serial command processor
• Actuator-specific safety configuration
• Multiple schedules per relay
• Scheduling across midnight
• Sensor-based automation rules
• Persistent configuration
• RTC and network time integration
• Wi-Fi and REST API integration
• Logging and alerts
• Automated tests

This subsystem is part of a larger project for monitoring and automating an indoor hydroponics environment.

The long-term goal is to connect relay control with:

• Environmental and water-quality sensors
• Configurable schedules
• Automation rules
• Operating modes and cultivation profiles
• Persistent storage
• Remote monitoring
• Backend and dashboard integration

Developed by Agustín Yañez.