The 1/8 Inch Water Flow Sensor YF-S401 measures liquid volume passing through a pipe by spinning a small hall-effect paddle wheel inside the housing. Each rotation generates a pulse on the signal wire, and the water flow sensor counts those pulses to calculate flow rate. Operating on DC 5V to 24V, it covers a measurement range of approximately 0.3 to 6 L/min and fits inlet pipe diameters between 2.5 and 4 mm. Weighing roughly 15 to 20 grams, it adds almost no mass to a portable build.
The YF-S401 water sensor outputs a pulse-frequency signal, not an analog voltage. That means you read it on a digital interrupt pin rather than an analog input, which many builders miss when first wiring it up. A non-obvious point: the pulse frequency is proportional to flow rate, so at very low flows near 0.3 L/min the pulse interval stretches long enough that a short polling loop will undercount it. Reading on an interrupt instead of a loop solves this completely. One honest limitation is that the 1/8 inch water flow sensor is rated for clean water; sediment or particulates will jam the paddle and give false zero readings over time.
Hobbyists making coffee volume counters, and engineers prototyping water flow sensor YF-S401 Arduino projects all use this module regularly. It works with the Arduino IDE, MicroPython, and any platform that supports external interrupt pins. StemVolt provides this sensor with trusted quality, ensuring reliable performance and easy usability.
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Features:
- Operating voltage of DC 5V to 24V lets you power the YF-S401 directly from an Arduino 5V pin
- Flow range of 0.3 to 6 L/min covers drip-rate dispensing up to moderate tap-pressure flow measurement
- Inlet pipe connection of 2.5 to 4 mm inner diameter fits common laboratory and aquarium tubing sizes
- Insulation resistance greater than 100 MOhm keeps signal integrity intact even in humid wet environments
Technical specifications:
| Specification | Details |
|---|---|
| Sensor Model | YF-S401 |
| Operating Voltage | DC 5V~24V |
| Operating Current | 0.015A |
| Connection | 6mm |
| Max Water Flow (L/min) | ~0.3 to 6 |
| Insulation Resistance (MOhm) | >100 |
| Inlet Water Pipe Diameter | 2.5–4mm |
| Weight | Approx. 15–20 gm |
Applications:
- A drip irrigation controller reads pulse output to log daily water usage per garden zone accurately
- A lab reagent dispenser uses the YF-S401 to stop a peristaltic pump after a precise millilitre count
- A portable water flow sensor yf s201 replacement build fits the YF-S401 into tighter 4 mm tubing rigs
Package includes:
- 1 x Water Flow Sensor YF-S401
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