How to wire The TDS (Total Dissolved Solids) Water Quality Monitoring Sensor Module Board

Introductions

Water is the essence of life, the fundamental resource that sustains all living creatures on Earth. Since the beginning of time, water has been the cradle of existence, shaping ecosystems and nurturing civilizations. The quality of drinking water is paramount—it must contain essential minerals in proper amounts, maintain safe levels of dissolved solids, and remain free from harmful contaminants to support health and well-being.

There is an important distinction between pure water and distilled water. Pure water, typically used for drinking, retains beneficial minerals and ions that contribute to its taste and nutritional value. In contrast, distilled water undergoes a process that removes all impurities, resulting in the purest form of water—devoid of minerals and other dissolved substances, making it unsuitable for regular consumption.

Interestingly, while water in its purest form is tasteless, the presence of dissolved solids—known as Total Dissolved Solids (TDS)—gives it distinct characteristics. Purified drinking water often has a subtle bitter note due to added minerals, while natural sources like borewell water may taste slightly sweet because of its mineral content. Distilled water, however, lacks any discernible taste since all dissolved substances have been removed. This variation in taste underscores the critical role TDS plays in determining water quality and its suitability for drinking.

The Total Dissolved Solids (TDS) content in water can be accurately measured using specialized sensors. These devices detect water conductivity and process the signal into a digital TDS reading. The fundamental principle involves a two-electrode system powered by a voltage source, where dissolved ions create measurable current flow between the electrodes.

Modern TDS sensors significantly improve upon this basic method by incorporating advanced features. These integrated modules automatically regulate the electric field strength and include built-in temperature compensation for greater accuracy. Many models now feature auto-zeroing capabilities and digital signal processing, eliminating the need for manual calibration in most applications. While traditional methods required calibration using buffer solutions, most contemporary sensors arrive factory-calibrated and ready for immediate use, though verification with reference solutions remains recommended for precision-critical applications.

The evolution from basic electrode systems to smart digital sensors has greatly simplified water quality testing while improving reliability and repeatability of measurements.

The TDS sensor operates across a wide voltage range of 3.3V to 5.5V, producing a 0-2.3V analog output signal, ensuring full compatibility with both 5V and 3.3V control systems. Its innovative AC excitation source design prevents electrode polarization, significantly enhancing probe longevity while maintaining stable output signal quality.

The waterproof probe construction allows for continuous immersion during long-term water quality monitoring. For accurate measurements in non-standard conditions, note that when testing water significantly above room temperature (25°C), an external temperature sensor must be integrated to provide proper temperature compensation.

Requirements for this lab

Arduino IDE | PlatformIO | Visual Studio Code
ARDUINO BOARDS & OTHER COMPATIBLE BOARDS
TDS Sensor Module Board with Probe
OLED Display Module
DS18B20 Temperature Sensor (Optional)
Resistors (See below required values)
Others (See below diagram for other requirements)

i2C Address Finder

This I2C address finder tool quickly identifies your OLED display’s communication address – simply upload the provided code to your Arduino board and open the Serial Monitor (found under Tools → Serial Monitor) to view the detected address. The scanner works seamlessly with common OLED displays including 128×64 and 128×32 pixel models, requiring only basic I2C connections (typically SDA to pin A4 and SCL to pin A5 on standard Arduino boards) for reliable detection. This straightforward solution eliminates guesswork when setting up your display interface, providing instant confirmation of your device’s correct I2C address through a simple upload-and-check process.

#include <Wire.h> // I2C library, required for MLX90614
#include <SparkFunMLX90614.h> 
IRTherm therm; // Create an IRTherm object to interact with throughout
void setup() 
{
  Serial.begin(9600); // Initialize Serial to log output
  therm.begin(); // Initialize the MLX90614
  if (therm.readID()) // Read from the ID registers
  { // If the read succeeded, print the ID:
    Serial.println("ID: 0x" + 
                   String(therm.getIDH(), HEX) +
                   String(therm.getIDL(), HEX));
  }
}
void loop() 
{

}

#include <Wire.h> // I2C library, required for MLX90614

#include <SparkFunMLX90614.h>

IRTherm therm; // Create an IRTherm object to interact with throughout

void setup()

{

Serial.begin(9600); // Initialize Serial to log output

therm.begin(); // Initialize the MLX90614

if (therm.readID()) // Read from the ID registers

{ // If the read succeeded, print the ID:

Serial.println("ID: 0x" +

String(therm.getIDH(), HEX) +

String(therm.getIDL(), HEX));

}

void loop()

{

}

Test Code TDS (Arduino Code)

// Include required libraries for I2C communication, graphics, and OLED display
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// OLED display configuration (128x64 pixels with hardware reset pin)
#define OLED_RESET 1
Adafruit_SSD1306 display(128, 64, &Wire, OLED_RESET);

// TDS sensor configuration
#define TdsSensorPin A1        // Analog input pin for TDS sensor
#define VREF 5.0               // Reference voltage for ADC (5V for Arduino)
#define SCOUNT 30              // Number of samples for median filtering
int analogBuffer[SCOUNT];      // Circular buffer for raw ADC readings
int analogBufferTemp[SCOUNT];  // Temporary buffer for processing
int analogBufferIndex = 0, copyIndex = 0;
float averageVoltage = 0, tdsValue = 0, temperature = 25;  // Default temp 25°C

void setup() {
  Serial.begin(115200);        // Initialize serial communication
  pinMode(TdsSensorPin, INPUT); // Configure TDS sensor pin as input
  Wire.begin();               // Initialize I2C communication
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // Initialize OLED with I2C address 0x3C
  display.clearDisplay();     // Clear display buffer
}

void loop() {
  // Sample TDS sensor every 40ms (25Hz sampling rate)
  static unsigned long analogSampleTimepoint = millis();
  if(millis()-analogSampleTimepoint > 40U) {
    analogSampleTimepoint = millis();
    analogBuffer[analogBufferIndex] = analogRead(TdsSensorPin); // Store reading
    analogBufferIndex = (analogBufferIndex + 1) % SCOUNT;      // Circular buffer
  }

  // Process and display readings every 800ms
  static unsigned long printTimepoint = millis();
  if(millis()-printTimepoint > 800U) {
    printTimepoint = millis();
    
    // Copy readings to temp buffer for processing
    for(copyIndex=0; copyIndex<SCOUNT; copyIndex++) {
      analogBufferTemp[copyIndex] = analogBuffer[copyIndex];
    }
    
    // Calculate median voltage (noise filtering) and convert to volts
    averageVoltage = getMedianNum(analogBufferTemp,SCOUNT) * (float)VREF / 1024.0;
    
    // Apply temperature compensation (formula for 25°C reference)
    float compensationCoefficient = 1.0 + 0.02*(temperature - 25.0);
    float compensationVoltage = averageVoltage / compensationCoefficient;
    
    // Convert compensated voltage to TDS value (cubic approximation)
    tdsValue = (133.42*pow(compensationVoltage,3) - 255.86*pow(compensationVoltage,2) 
               + 857.39*compensationVoltage)*0.5;
    // Serial.print("voltage:");
    // Serial.print(averageVoltage,2);
    // Serial.print("V");

    // Serial output for debugging
    Serial.print("TDS Value:");
    Serial.print(tdsValue,0);
    Serial.println("ppm");
    
    // OLED Display Output
    display.clearDisplay();
    display.setTextSize(2);
    display.setTextColor(WHITE);
    
    // Display TDS label
    display.setCursor(0,0);
    display.print("TDS Value:");
    
    // Display TDS value
    display.setCursor(30,30);
    display.print(tdsValue,0);
    
    // Display units
    display.setCursor(80,28);
    display.print("ppm");
    display.display();
  }
}

/**
 * Median filter algorithm for noise reduction
 * @param bArray Input array of sensor readings
 * @param iFilterLen Number of elements in array
 * @return Median value of the array
 */
int getMedianNum(int bArray[], int iFilterLen) {
  int bTab[iFilterLen];  // Temporary working array
  
  // Copy input array
  for (byte i = 0; i<iFilterLen; i++) {
    bTab[i] = bArray[i];
  }
  
  // Sort array using bubble sort
  int i, j, bTemp;
  for (j = 0; j < iFilterLen - 1; j++) {
    for (i = 0; i < iFilterLen - j - 1; i++) {
      if (bTab[i] > bTab[i + 1]) {
        bTemp = bTab[i];
        bTab[i] = bTab[i + 1];
        bTab[i + 1] = bTemp;
      }
    }
  }
  
  // Return median (middle value for odd-length, average of middle two for even)
  if ((iFilterLen & 1) > 0) {
    return bTab[(iFilterLen - 1) / 2];
  } else {
    return (bTab[iFilterLen / 2] + bTab[iFilterLen / 2 - 1]) / 2;
  }
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

// Include required libraries for I2C communication, graphics, and OLED display

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

// OLED display configuration (128x64 pixels with hardware reset pin)

#define OLED_RESET 1

Adafruit_SSD1306 display(128, 64, &Wire, OLED_RESET);

// TDS sensor configuration

#define TdsSensorPin A1 // Analog input pin for TDS sensor

#define VREF 5.0 // Reference voltage for ADC (5V for Arduino)

#define SCOUNT 30 // Number of samples for median filtering

int analogBuffer[SCOUNT]; // Circular buffer for raw ADC readings

int analogBufferTemp[SCOUNT]; // Temporary buffer for processing

int analogBufferIndex = 0, copyIndex = 0;

float averageVoltage = 0, tdsValue = 0, temperature = 25; // Default temp 25°C

void setup() {

Serial.begin(115200); // Initialize serial communication

pinMode(TdsSensorPin, INPUT); // Configure TDS sensor pin as input

Wire.begin(); // Initialize I2C communication

display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // Initialize OLED with I2C address 0x3C

display.clearDisplay(); // Clear display buffer

}

void loop() {

// Sample TDS sensor every 40ms (25Hz sampling rate)

static unsigned long analogSampleTimepoint = millis();

if(millis()-analogSampleTimepoint > 40U) {

analogSampleTimepoint = millis();

analogBuffer[analogBufferIndex] = analogRead(TdsSensorPin); // Store reading

analogBufferIndex = (analogBufferIndex + 1) % SCOUNT; // Circular buffer

}

// Process and display readings every 800ms

static unsigned long printTimepoint = millis();

if(millis()-printTimepoint > 800U) {

printTimepoint = millis();

// Copy readings to temp buffer for processing

for(copyIndex=0; copyIndex<SCOUNT; copyIndex++) {

analogBufferTemp[copyIndex] = analogBuffer[copyIndex];

}

// Calculate median voltage (noise filtering) and convert to volts

averageVoltage = getMedianNum(analogBufferTemp,SCOUNT) * (float)VREF / 1024.0;

// Apply temperature compensation (formula for 25°C reference)

float compensationCoefficient = 1.0 + 0.02*(temperature - 25.0);

float compensationVoltage = averageVoltage / compensationCoefficient;

// Convert compensated voltage to TDS value (cubic approximation)

tdsValue = (133.42*pow(compensationVoltage,3) - 255.86*pow(compensationVoltage,2)

+ 857.39*compensationVoltage)*0.5;

// Serial.print("voltage:");

// Serial.print(averageVoltage,2);

// Serial.print("V");

// Serial output for debugging

Serial.print("TDS Value:");

Serial.print(tdsValue,0);

Serial.println("ppm");

// OLED Display Output

display.clearDisplay();

display.setTextSize(2);

display.setTextColor(WHITE);

// Display TDS label

display.setCursor(0,0);

display.print("TDS Value:");

// Display TDS value

display.setCursor(30,30);

display.print(tdsValue,0);

// Display units

display.setCursor(80,28);

display.print("ppm");

display.display();

}

/**

* Median filter algorithm for noise reduction

* @param bArray Input array of sensor readings

* @param iFilterLen Number of elements in array

* @return Median value of the array

int getMedianNum(int bArray[], int iFilterLen) {

int bTab[iFilterLen]; // Temporary working array

// Copy input array

for (byte i = 0; i<iFilterLen; i++) {

bTab[i] = bArray[i];

}

// Sort array using bubble sort

int i, j, bTemp;

for (j = 0; j < iFilterLen - 1; j++) {

for (i = 0; i < iFilterLen - j - 1; i++) {

if (bTab[i] > bTab[i + 1]) {

bTemp = bTab[i];

bTab[i] = bTab[i + 1];

bTab[i + 1] = bTemp;

}

// Return median (middle value for odd-length, average of middle two for even)

if ((iFilterLen & 1) > 0) {

return bTab[(iFilterLen - 1) / 2];

} else {

return (bTab[iFilterLen / 2] + bTab[iFilterLen / 2 - 1]) / 2;

}

Test Code Version 2

This Arduino code creates a water quality monitoring system that measures Total Dissolved Solids (TDS) using a specialized sensor. The system consists of three main components: a TDS sensor that connects to analog pin A1, an I2C-connected OLED display for showing results, and the Arduino board that processes the data. At startup, the code initializes serial communication at 115200 baud for debugging and sets up the TDS sensor with important parameters including the 5V reference voltage (matching Arduino UNO’s specification) and 10-bit analog resolution. The OLED display is prepared with a 128×64 pixel resolution and checked for proper connection – if initialization fails, the system halts to prevent incorrect readings.

The core measurement process runs continuously in the main loop. Every cycle, it takes a new TDS reading while applying automatic temperature compensation (using either a default 25°C value or an actual temperature reading if a sensor is connected). The GravityTDS library handles the complex calculations, converting the raw analog signal into a meaningful parts-per-million (ppm) value that represents water purity. Results are output both to the Serial Monitor for debugging and prominently displayed on the OLED screen with large, readable numbers. The display updates every second, showing the current TDS value in ppm along with a clear label. For accuracy, the system automatically compensates for water temperature variations, as TDS readings are temperature-dependent. The code structure allows for easy integration of additional sensors, with clear markers showing where to add temperature sensor functionality if needed.

This implementation provides a reliable, user-friendly water quality monitoring solution that’s particularly useful for applications like drinking water analysis, aquarium maintenance, hydroponic systems, and industrial water treatment processes. The combination of immediate visual feedback through the OLED and detailed serial output makes it versatile for both standalone use and connected systems.

// Include required libraries:
#include <EEPROM.h>          // For storing calibration data
#include "GravityTDS.h"     // TDS sensor library
#include <Wire.h>           // I2C communication
#include <Adafruit_GFX.h>   // Core graphics library
#include <Adafruit_SSD1306.h> // OLED display library

// TDS Sensor Configuration
#define TdsSensorPin A1      // Analog pin for TDS sensor input
GravityTDS gravityTds;       // Create TDS sensor instance

// OLED Display Configuration
#define SCREEN_WIDTH 128     // OLED width in pixels
#define SCREEN_HEIGHT 64    // OLED height in pixels
#define OLED_RESET -1       // Reset pin (-1 for shared reset)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Measurement Variables
float temperature = 25;     // Default water temperature (25°C)
float tdsValue = 0;         // Stores calculated TDS value

void setup() {
  Serial.begin(115200);     // Initialize serial communication
  
  // Configure TDS sensor
  gravityTds.setPin(TdsSensorPin);          // Set measurement pin
  gravityTds.setAref(5.0);                 // Reference voltage (5V for Arduino UNO)
  gravityTds.setAdcRange(1024);            // 10-bit ADC resolution (0-1023)
  gravityTds.begin();                      // Initialize TDS sensor
  
  // Initialize OLED display
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while(true); // Halt if display initialization fails
  }
  
  // Display startup screen
  display.display();       // Show initial buffer
  delay(2);                // Brief pause
  display.clearDisplay();  // Clear display
  
  // Show welcome message
  display.setTextColor(WHITE);
  display.setTextSize(2);
  display.setCursor(0,5);
  display.print("TDS Sensor");
  display.display();
  delay(3000); // Display welcome for 3 seconds
}

void loop() {
  // Uncomment to add temperature sensor functionality:
  // temperature = readTemperature(); 
  
  // Configure TDS measurement with temperature compensation
  gravityTds.setTemperature(temperature); // Set current water temperature
  gravityTds.update();                    // Take new measurement
  tdsValue = gravityTds.getTdsValue();    // Get calculated TDS value
  
  // Output to Serial Monitor
  Serial.print(tdsValue,0);  // Print TDS value (no decimal places)
  Serial.println("ppm");     // Print units
  
  // Update OLED Display
  display.clearDisplay();
  
  // Display TDS label
  display.setTextSize(2);
  display.setCursor(20,0);
  display.println("TDS Value");
  
  // Display TDS reading
  display.setTextSize(3);
  display.setCursor(30,30);
  display.print(tdsValue);  // Show numeric value
  
  display.display(); // Refresh OLED
  
  delay(1000); // Update every second
}

// Include required libraries:

#include <EEPROM.h> // For storing calibration data

#include "GravityTDS.h" // TDS sensor library

#include <Wire.h> // I2C communication

#include <Adafruit_GFX.h> // Core graphics library

#include <Adafruit_SSD1306.h> // OLED display library

// TDS Sensor Configuration

#define TdsSensorPin A1 // Analog pin for TDS sensor input

GravityTDS gravityTds; // Create TDS sensor instance

// OLED Display Configuration

#define SCREEN_WIDTH 128 // OLED width in pixels

#define SCREEN_HEIGHT 64 // OLED height in pixels

#define OLED_RESET -1 // Reset pin (-1 for shared reset)

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Measurement Variables

float temperature = 25; // Default water temperature (25°C)

float tdsValue = 0; // Stores calculated TDS value

void setup() {

Serial.begin(115200); // Initialize serial communication

// Configure TDS sensor

gravityTds.setPin(TdsSensorPin); // Set measurement pin

gravityTds.setAref(5.0); // Reference voltage (5V for Arduino UNO)

gravityTds.setAdcRange(1024); // 10-bit ADC resolution (0-1023)

gravityTds.begin(); // Initialize TDS sensor

// Initialize OLED display

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

Serial.println(F("SSD1306 allocation failed"));

while(true); // Halt if display initialization fails

}

// Display startup screen

display.display(); // Show initial buffer

delay(2); // Brief pause

display.clearDisplay(); // Clear display

// Show welcome message

display.setTextColor(WHITE);

display.setTextSize(2);

display.setCursor(0,5);

display.print("TDS Sensor");

display.display();

delay(3000); // Display welcome for 3 seconds

}

void loop() {

// Uncomment to add temperature sensor functionality:

// temperature = readTemperature();

// Configure TDS measurement with temperature compensation

gravityTds.setTemperature(temperature); // Set current water temperature

gravityTds.update(); // Take new measurement

tdsValue = gravityTds.getTdsValue(); // Get calculated TDS value

// Output to Serial Monitor

Serial.print(tdsValue,0); // Print TDS value (no decimal places)

Serial.println("ppm"); // Print units

// Update OLED Display

display.clearDisplay();

// Display TDS label

display.setTextSize(2);

display.setCursor(20,0);

display.println("TDS Value");

// Display TDS reading

display.setTextSize(3);

display.setCursor(30,30);

display.print(tdsValue); // Show numeric value

display.display(); // Refresh OLED

delay(1000); // Update every second

}

Downloads

Download TDS GravityTDS Code Library
Download DallasTemperature Code Library for DS18B20
Download TDS SENSOR / Water Quality Sensor Module Datasheet / Schematics
Download CD4060BM Datasheet
Download LMV324 Datasheet
Download TPS60400DBR Datasheet
Download ME6206A30M3G Datasheet

How to wire The TDS (Total Dissolved Solids) Water Quality Monitoring Sensor Module Board

Introductions

Requirements for this lab

i2C Address Finder

Test Code TDS (Arduino Code)

Test Code Version 2

Downloads

Related Article:

Leave a Reply Cancel reply

Important Cookie Information :