The FS400A is a G1-inch DN25 water flow sensor that uses a Hall-effect sensor to measure the flow rate of water. It provides pulse signals that correspond to the flow rate in liters per minute (L/min). This sensor is ideal for applications like water metering, irrigation systems, and industrial flow monitoring.

Components Required:

• Arduino Uno (or compatible board)
• FS400A G1” DN25 Water Flow Sensor
• 10kΩ pull-up resistor (optional, for stable signal)
• Jumper wires
• 5V Power source (from Arduino’s 5V pin)

Wiring Diagram:

Notes:

• The signal wire (yellow) provides pulses proportional to the flow rate.
• A 10kΩ pull-up resistor can be connected between the signal (yellow) and VCC (5V) for noise reduction.
• Ensure the arrow on the sensor matches the water 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 / 4.8) = Flow Rate in L/min
        flowRate = (pulseCount / 4.8);  

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

        pulseCount = 0;  // Reset pulse count
    }
}

How It Works:

1. The FS400A water flow sensor generates pulses as water flows.
2. The Arduino interrupt (pin 2) detects these pulses.
3. The pulse count is converted to L/min using the formula: Flow Rate (L/min)=Pulse Count4.8\text{Flow Rate (L/min)} = \frac{\text{Pulse Count}}{4.8} (4.8 is a manufacturer-provided calibration constant).
4. The flow rate is displayed on the Serial Monitor.