Architecture

🏊 Smart Swimming Pool: System architecture and data flow overview.

This page describes how the hardware components, software modules, and communication protocols work together in a typical Smart Swimming Pool installation.

System Overview

The following diagram shows all major components and how they connect:

    flowchart LR
    subgraph Sensors["🌡️ Sensors (Low Voltage)"]
        S1[DS18B20<br/>Solar Collector] -->|GPIO32<br/>OneWire| ESP
        S2[DS18B20<br/>Pool Water] -->|GPIO33<br/>OneWire| ESP
    end

    subgraph Controller["🎛️ Pool Controller"]
        ESP[ESP32<br/>Pool Controller<br/>Firmware v3.x]
        WEB[Web Interface<br/>LittleFS<br/>Configuration UI]
        ESP --- WEB
    end

    subgraph Relay["🔌 Relay Module (Low Voltage)"]
        R[2-Channel<br/>Relay Module<br/>GPIO 25/26]
    end

    subgraph Mains["⚡ Mains Voltage (230V)"]
        P1[Heating Circuit<br/>Pump]
        P2[Filter/Circulation<br/>Pump]
        RCD[FI / RCD<br/>Circuit Breaker]
    end

    subgraph Network["🌐 Network"]
        MQTT[MQTT Broker<br/>Mosquitto]
    end

    subgraph SmartHome["🏠 Smart Home (Optional)"]
        HA[Home Assistant<br/>MQTT Discovery]
        OH[openHAB<br/>MQTT Binding]
        GRAF[Grafana<br/>Dashboard]
    end

    subgraph Display["🖥️ Optional Modules"]
        PM[Pool Monitor<br/>Wireless Display]
    end

    %% Connections
    ESP -->|GPIO 25/26<br/>Active-Low| R
    ESP -->|MQTT<br/>HA Discovery / Homie| MQTT

    R -->|230V via RCD| Mains
    RCD --- P1
    RCD --- P2

    MQTT --> HA
    MQTT --> OH
    MQTT --> GRAF
    MQTT --> PM
  

Diagram Legend

Component Descriptions

Sensors (Low Voltage)

Both sensors share the same 3.3V supply and GND. Each data line requires a 4.7kΩ pull-up resistor to 3.3V.

Pool Controller

The ESP32 runs the pool controller firmware, which:

• Reads both DS18B20 temperature sensors via OneWire protocol
• Implements heating logic (hysteresis, temperature thresholds)
• Controls circulation scheduling (timer, temperature-based)
• Publishes all data via MQTT using the Home Assistant MQTT Discovery format (v3.x) or Homie convention (v2.x)
• Provides a web interface for configuration (LittleFS)
• Accepts commands via MQTT and web UI
• Operates fully autonomously — no smart home server required

Relay Module

A standard 2-channel 5V relay module (active-low):

The relay module provides galvanic isolation between the ESP32 (low voltage) and the pumps (230V). Always connect pumps through an RCD/FI circuit breaker.

Mains Voltage Side (230V)

• Heating circuit pump: Circulates pool water through the heat exchanger
• Filter/circulation pump: Runs the sand filter system on a schedule
• RCD / FI: Mandatory safety device — protects against ground faults
• Circuit breaker: Overcurrent protection for each pump circuit

⚠️ All 230V wiring must comply with local electrical codes. If unsure, consult a licensed electrician.

Data Flow

1. Sensor Reading: ESP32 reads temperatures from DS18B20 sensors via OneWire
2. Control Logic: Firmware evaluates heating and circulation rules (autonomous, no server needed)
3. MQTT Publication: All sensor values, switch states, and diagnostics are published to the MQTT broker using the Home Assistant MQTT Discovery format (v3.x)
4. Smart Home Integration: Home Assistant, openHAB, or Grafana subscribe to MQTT topics for visualization and automation
5. Actuation: ESP32 drives the relay module to switch pumps on/off

Key Design Decisions

Optional Modules

The architecture supports several optional add-ons:

Related Pages

• Getting Started — Build your own pool controller
• Home Assistant Integration — Dashboard and automation guide
• FAQ & Troubleshooting — Common problems and solutions