1/8 inch DN4 Water flow sensor is connected to the 6mm hoses, the hall sensor YF-S401 White

Description

The YF-S401 is a compact Hall-effect water flow sensor designed for low-flow liquid measurement in Arduino, ESP32, and other microcontroller projects. It features a 1/8-inch (DN4) inner diameter connection with a 7mm outer diameter, specifically intended for use with 6mm flexible hoses—making it ideal for coffee machines, water dispensers, laboratory setups, and small-scale irrigation systems where standard 1/2-inch sensors would be too large .

The sensor consists of a plastic valve body containing a magnetic pinwheel rotor and a Hall-effect sensor. As water flows through, the rotor spins at a rate proportional to the flow velocity, and the Hall sensor outputs a digital pulse train. The pulse frequency is directly proportional to flow rate, allowing the microcontroller to calculate instantaneous flow (L/min) and cumulative volume (liters). The YF-S401 is rated for a flow range of 0.3–6 L/min, with a pulse characteristic of 5880 pulses per liter (5.88 pulses per mL) .

The sensor operates from 5V to 12V DC (some sources list 3.5–24V tolerance) with a typical current draw of 15mA and outputs a 5V TTL-level pulse (high level >4.5V at 5V supply) . Accuracy is specified at ±5%, making it suitable for relative monitoring and control rather than precision metering . The body is made of plastic with a stainless steel impeller shaft for durability, and the unit is designed for vertical installation with a maximum tilt of 5 degrees .

Critical limitations: This is a low-cost, non-certified sensor intended for educational, hobbyist, and light commercial use. The pulse rate can vary with flow rate, pressure, and orientation, and calibration against a known volume is recommended for better precision. For 3.3V microcontrollers (ESP32, ESP8266), the 5V pulse output requires a logic level shifter or voltage divider to protect the GPIO pins. The sensor is not suitable for corrosive chemicals, and liquid temperature should not exceed 120°C .

Features

• Compact 1/8″ (DN4) Connection: Designed for 6mm hoses, ideal for low-flow applications where larger sensors won’t fit .

• Hall-Effect Pulse Output: Digital square wave proportional to flow rate, readable by any microcontroller with an interrupt-capable GPIO.

• Low-Flow Measurement Range (0.3–6 L/min): Suitable for coffee machines, water dispensers, and precision dosing systems .

• 5880 Pulses per Liter: High pulse density provides good resolution for volume tracking .

• 5V TTL Output: Directly compatible with 5V Arduino boards; 3.3V systems require level shifting.

• Stainless Steel Impeller Shaft: Durable construction for long-term reliability .

• Low Power Consumption: 15mA typical at 5V, suitable for embedded applications .

• Vertical Installation Design: Optimized for vertical mounting with ≤5° tilt for reliable rotor movement .

Technical Specifications