1. Product Description

The YF-S402 Water Flow Sensor is a compact and lightweight sensor designed to measure the flow rate of water in pipes and fluid-handling systems. It uses a turbine-type rotor and a Hall effect sensor to detect water movement and generate digital pulses corresponding to the flow rate.

When water passes through the sensor, the internal magnetic rotor spins. The Hall effect sensor detects this rotation and produces a pulse signal whose frequency varies with the flow rate. By connecting the sensor to a microcontroller such as an Arduino, ESP32, or other compatible controller, users can monitor water flow, estimate water consumption, and develop automated water management systems.

Operating with a supply voltage of 5V to 24V DC and supporting a stated flow range of 0.3 to 6 litres per minute, the YF-S402 is suitable for smart irrigation, water dispensers, coffee machines, plumbing projects, and water monitoring applications.

2. Features

• Digital Pulse Output: Generates pulses proportional to the water flow rate.

• Hall Effect Sensing: Detects the rotation of the internal magnetic rotor.

• Wide Operating Voltage: Supports a supply voltage of 5V to 24V DC.

• Flow Measurement: Designed for flow rates from 0.3 to 6 litres per minute.

• Compact and Lightweight: Easy to integrate into water monitoring systems.

• Sealed Construction: Includes a sealing ring to help prevent leakage when properly installed.

• Stainless Steel Axis: Provides durability and abrasion resistance.

• Microcontroller Compatibility: Can be interfaced with compatible digital input pins.

• Versatile Applications: Suitable for irrigation, plumbing, water dispensers, coffee machines, and automation projects.

• RoHS Compliance: Listed as RoHS compliant; verify the manufacturer’s documentation if certification is required.

3. Specifications

Note: The supplied information does not specify the exact pulse-to-volume calibration factor, measurement accuracy, maximum water pressure, or output voltage levels. These should be confirmed before designing a measurement system.

4. Design and Construction

The YF-S402 consists of a plastic valve body, an internal turbine rotor with a magnet, a Hall effect sensing element, and a sealing ring. The water flows through the sensor body and rotates the internal rotor.

A stainless steel axis supports the rotor and helps provide wear resistance. The compact construction makes the sensor suitable for integration into small water pipes and equipment where space is limited.

The pipe connection dimensions are specified as an inner diameter of 8.5 mm and an outer diameter of 11 mm. Check the physical dimensions and connection compatibility before installation.

5. Working Principle

The YF-S402 measures water flow by converting the rotation of an internal turbine into electrical pulses.

1. Water Flow: Water enters the sensor and passes through the internal turbine.

2. Rotor Rotation: The flowing water causes the magnetic rotor to spin.

3. Magnetic Detection: The Hall effect sensor detects the rotating magnetic field.

4. Pulse Generation: The sensor generates a digital pulse signal.

5. Flow Calculation: A microcontroller counts the pulses over time and uses the sensor’s calibration factor to estimate flow rate and total water volume.

The pulse frequency generally increases as the flow rate increases. However, the precise relationship between pulse frequency and litres per minute depends on the sensor’s calibration.

6. Applications

• Agriculture and Irrigation: Monitor water flow in irrigation and automated watering systems.

• HVAC Systems: Measure water movement in compatible heating, ventilation, and air-conditioning systems.

• Plumbing Systems: Monitor water flow in residential and commercial installations.

• Water Treatment: Track water flow through compatible treatment equipment.

• Smart Home Automation: Monitor water usage and support leak-detection projects.

• Automatic Water Dispensers: Measure water delivery in dispensing equipment.

• Coffee Machines: Monitor water flow during brewing.

• DIY Electronics: Build water flow monitoring and control projects using Arduino or ESP32.

• Water Management Systems: Estimate consumption and automate compatible pumps or valves.

7. Interfacing with Microcontrollers

The YF-S402 can be connected to a compatible microcontroller through its power, ground, and pulse-output connections. The microcontroller counts the digital pulses to calculate the flow rate.

When interfacing with an Arduino, ESP32, or another controller:

• Supply the sensor with a voltage within its specified operating range.

• Connect the sensor ground and controller ground together.

• Connect the pulse output to a compatible digital input.

• Confirm the sensor’s output voltage before connecting it directly to a microcontroller input. An ESP32 uses 3.3V logic and its GPIO pins are not 5V tolerant.

• Use the correct calibration factor to calculate flow rate and total volume.

• Ensure all pipe connections are secure and leak-free before operating the system.

8. Package Includes

– 1 × YF-S402 Water Flow Sensor

9. Product Disclaimer

• The specified flow range and pulse frequency are based on the supplied product information. Actual performance may vary depending on water pressure, installation, flow conditions, and sensor calibration.

• The exact pulse calibration factor and measurement accuracy are not provided. Calibration may be required for reliable flow measurement.

• Confirm the sensor’s connection dimensions, output voltage, maximum operating pressure, and compatibility with the intended liquid before installation.

• The sensor is described for water flow measurement. Compatibility with other liquids should not be assumed without checking the manufacturer’s specifications.

• Use suitable pipe fittings and sealing methods to prevent leakage. Keep electronic connections protected from moisture.

• Product images are for illustration and representation purposes only. The actual product may slightly differ in appearance, colour, design, or component placement due to manufacturing variations and production batches.