1/2 Inch Water Flow Sensor - YF-S201

Overview

The YF-S201 Water Flow Sensor is a widely used module for measuring liquid flow rate and volume in pipes. It is commonly used in Arduino and IoT projects.

It is designed for 1/2-inch pipes and works by generating pulses as water flows through it.

Working Principle

• Inside the sensor a rotating impeller (fan)

• Water flow spins the impeller

• A Hall Effect sensor detects each rotation

• Each rotation generates a pulse

By counting pulses, you can calculate:

• Flow rate (L/min)

• Total volume (Liters)

Example formula:

• Flow rate (L/min) = Frequency / 7.5

Infographic Summary

p YF-S201 FLOW SENSOR Function: Measure water Flow Range: 130 L/min Voltage: 5V 18V Output: Pulse Signal Type: Hall Effect Sensor Size: 1/2 inch pipe Accuracy: 10%

Pin Configuration

YF-S201 Red VCC (518V) Black GND Yellow Pulse Output

Key Specifications

• Operating Voltage: 5V 18V DC

• Flow Range: 1 to 30 L/min

• Output: Digital pulse (TTL)

• Pulses per Liter: 450 pulses

• Accuracy: 10%

• Temperature: -25C to 80C

• Max Pressure: 2.0 MPa

Key Features

• Measures both flow rate & total water usage

• Low power consumption (~15mA)

• Easy to install inline with pipe

• Stable pulse output for microcontrollers

• Low-cost and reliable

Applications

• Smart water meters

• Irrigation systems

• Home automation (water monitoring)

• Beverage dispensing machines

• Arduino/ESP32 projects

• Raspberry Pi

Connect pulse output to a digital interrupt pin to count pulses.

Important Notes

• Must follow flow direction arrow for accurate results

• Needs calibration for precise measurement

• Not suitable for dirty or corrosive liquids

• Minimum flow required to rotate impeller

From real user experience (Reddit insight):

Reverse flow may work but gives inaccurate readings

YF-S201 vs Other Flow Sensors