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IoTSpark
Water Quality Monitoring System
Intermediate20/6/2026- Author: IoTSpark Maker

Water Quality Monitoring System

Build a water quality monitoring system that measures temperature, TDS, pH, and turbidity, shows an alert status, and can be extended to send real-time data over MQTT. Suited for monitoring fish tank, hydroponic, or water tank quality, or as a reference monitoring model. Note: readings from consumer-grade sensors do not replace certified testing equipment or lab analysis.

ESP32IoTWater QualityMQTTArduino IDETDSpHDS18B20
7 steps9 components
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Detailed guide

Part 2: System Architecture and Wiring Diagram

Covers the data architecture, pin connection table, and how to protect the ESP32's ADC pins when using analog sensors.

Updated 31/08/2026

Part 2: System Architecture and Wiring Diagram

The system has three main blocks: water sensors, the ESP32 processing data, and the display/alert/cloud block.

[Water Sensors]
  ├── DS18B20 Temperature Sensor
  ├── TDS Sensor
  ├── pH Sensor
  └── Turbidity Sensor
        │
        ▼
[ESP32]
  ├── Read sensor data
  ├── Filter noise
  ├── Compute measured values
  ├── Evaluate water status
  └── Send via Serial / MQTT / Dashboard
        │
        ▼
[Output]
  ├── Serial Monitor
  ├── LED / Buzzer
  ├── OLED Display
  └── MQTT Dashboard

2.1. Full Pin Connection Table

DeviceDevice PinESP32Note
DS18B20DATAGPIO4Needs a 4.7kΩ pull-up resistor.
TDS SensorAOGPIO34ADC1, input-only.
pH SensorAOGPIO35ADC1, input-only.
Turbidity SensorAOGPIO32Needs a voltage divider if the output exceeds 3.3V.
Green LEDAnodeGPIO26Indicates NORMAL status.
Red LEDAnodeGPIO27Indicates WARNING/DANGER.
BuzzerINGPIO25Activates on DANGER or SENSOR_ERROR.

2.2. Connecting the DS18B20

The DS18B20 uses the 1-Wire interface. Its DATA pin needs a 4.7kΩ pull-up resistor to 3.3V.

3.3V ----[4.7kΩ]---- DATA DS18B20
                    │
GPIO4 --------------┘
GND ---------------- GND DS18B20

2.3. Protecting the ESP32's ADC Pins

The ESP32 should only receive an analog signal up to about 3.3V. If the turbidity or pH module outputs higher, use a voltage divider.

AO Sensor ---- R1 10kΩ ----+---- GPIO32 ESP32
                           |
                         R2 20kΩ
                           |
                          GND

Voltage divider formula:

Vout = Vin × R2 / (R1 + R2)

With R1 = 10kΩ and R2 = 20kΩ, the ESP32 receives about 66.7% of the sensor's original voltage.