The YF-S201 water flow sensor is a Hall-effect sensor that measures the flow rate of water in liters per minute (L/min). It is widely used in water dispensers, irrigation systems, and other fluid monitoring applications.

Components Required:

• Arduino Uno (or any compatible board)
• YF-S201 Water Flow Sensor (G1/2" DN15)
• 10kΩ pull-up resistor (optional)
• Jumper wires
• 5V Power supply (Arduino’s 5V pin)

Wiring Diagram:

Notes:

• The signal wire (yellow) outputs pulses corresponding to the water flow rate.
• A 10kΩ pull-up resistor can be connected between the signal (yellow) and VCC (5V) for more stable readings.
• Ensure the arrow direction on the sensor is aligned with the flow direction.

Arduino Code:

volatile int pulseCount = 0;
float flowRate = 0.0;
unsigned long oldTime = 0;

void IRAM_ATTR pulseCounter() {
    pulseCount++;
}

void setup() {
    Serial.begin(9600);
    pinMode(2, INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(2), pulseCounter, FALLING);
}

void loop() {
    if (millis() - oldTime > 1000) {  // Update every second
        oldTime = millis();

        // Flow rate formula: (Pulse Count / 7.5) = Flow Rate in L/min
        flowRate = (pulseCount / 7.5);

        Serial.print("Flow Rate: ");
        Serial.print(flowRate);
        Serial.println(" L/min");

        pulseCount = 0;  // Reset pulse count
    }
}

How It Works

• The Hall sensor in YF-S201 generates pulses as water flows through it.
• The Arduino interrupt (pin 2) detects these pulses.
• The program counts pulses and calculates the flow rate using the formula: Flow Rate(L/min)=Pulse Count7.5\text{Flow Rate} (\text{L/min}) = \frac{\text{Pulse Count}}{7.5} (The value 7.5 is an empirical constant provided by the sensor manufacturer.)
• The result is displayed on the Serial Monitor.