Interfacing Water Flow Sensor with Arduino

Interfacing Water Flow Sensor with Arduino

Interfacing Water Flow Sensor with Arduino

Water Flow Sensor is used to determine the amount of water flowing through a certain pipe/ area.

Interfacing Water Flow Sensor with Arduino

Connections with Arduino:

Sensor Wire color Arduino Pins
Black GND
Green/ Red 5V
Yellow/ Orange 2


Arduino Code:

This code uses interrupts, which changes with the type of Arduino board. The information regarding Arduino interrupts can be obtained from here.

Board Digital Pins Usable For Interrupts
Uno, Nano, Mini, other 328-based 2, 3
Mega, Mega2560, MegaADK 2, 3, 18, 19, 20, 21
Micro, Leonardo, other 32u4-based 0, 1, 2, 3, 7
Zero all digital pins, except 4
MKR1000 Rev.1 0, 1, 4, 5, 6, 7, 8, 9, A1, A2
Due all digital pins
101 all digital pins


Here, we have used Interrupt zero (0) on Arduino Uno/ Mega, means we need to connect signal pin to digital pin 2 of Arduino.

Liquid flow rate sensor Arvind SanjeevMeasure the liquid/water flow rate using this code. 
Connect Vcc and Gnd of sensor to arduino, and the 
signal line to arduino digital pin 2.*/
byte statusLed = 13;

byte sensorInterrupt = 0; // 0 = digital pin 2
byte sensorPin = 2;

// The hall-effect flow sensor outputs approximately 4.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 4.5;

volatile byte pulseCount;

float flowRate;
unsigned int flowMilliLitres;
unsigned long totalMilliLitres;

unsigned long oldTime;

void setup()

// Initialize a serial connection for reporting values to the host

// Set up the status LED line as an output
pinMode(statusLed, OUTPUT);
digitalWrite(statusLed, HIGH); // We have an active-low LED attached

pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH);

pulseCount = 0;
flowRate = 0.0;
flowMilliLitres = 0;
totalMilliLitres = 0;
oldTime = 0;

// The Hall-effect sensor is connected to pin 2 which uses interrupt 0.
// Configured to trigger on a FALLING state change (transition from HIGH
// state to LOW state)
attachInterrupt(sensorInterrupt, pulseCounter, FALLING);

* Main program loop
void loop()

if((millis() - oldTime) > 1000) // Only process counters once per second
// Disable the interrupt while calculating flow rate and sending the value to
// the host

// Because this loop may not complete in exactly 1 second intervals we calculate
// the number of milliseconds that have passed since the last execution and use
// that to scale the output. We also apply the calibrationFactor to scale the output
// based on the number of pulses per second per units of measure (litres/minute in
// this case) coming from the sensor.
flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;

// Note the time this processing pass was executed. Note that because we've
// disabled interrupts the millis() function won't actually be incrementing right
// at this point, but it will still return the value it was set to just before
// interrupts went away.
oldTime = millis();

// Divide the flow rate in litres/minute by 60 to determine how many litres have
// passed through the sensor in this 1 second interval, then multiply by 1000 to
// convert to millilitres.
flowMilliLitres = (flowRate / 60) * 1000;

// Add the millilitres passed in this second to the cumulative total
totalMilliLitres += flowMilliLitres;

unsigned int frac;

// Print the flow rate for this second in litres / minute
Serial.print("Flow rate: ");
Serial.print(int(flowRate)); // Print the integer part of the variable
Serial.print("\t"); // Print tab space

// Print the cumulative total of litres flowed since starting
Serial.print("Output Liquid Quantity: "); 
Serial.print("\t"); // Print tab space

// Reset the pulse counter so we can start incrementing again
pulseCount = 0;

// Enable the interrupt again now that we've finished sending output
attachInterrupt(sensorInterrupt, pulseCounter, FALLING);

Insterrupt Service Routine
void pulseCounter()
// Increment the pulse counter


Results/ Output:

Interfacing Water Flow Sensor with Arduino

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