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Water Flow Sensor: What it is and How to Use One

Are you looking for a way to measure the volume of water you use in your home? It would help if you had a water flow sensor.

For effective water management, you’ll need to supply only the water you need for effective water management. F r this reason, it’s best to measure the water flow in your water management systems constantly.

Plus, there are various types of water flow sensors and measurement techniques. It’s enough to confuse you on which one to use for your circuit.

So, in this article, we’ll cover the different types of water sensors and how to use one with an Arduino.

What is a Water Flow Sensor?

Water flow sensors are devices that can measure water flow rates. I also measure the volume of liquid that passes per unit of time.

Plus, you can find water flow sensors in automatic water heaters, coffee machines (DIY and standard), and water vending machines.

Most water flow sensors include a water rotor and a hall-effect sensor built inside a copper body.

Furthermore, there are different types of water sensors available to choose from. 

However, it depends on the water you use, costs, and conditions for keeping. Moreover, water sensors can measure dirty water, slurries, and clean, cold, and hot water.

How does a Water Flow Sensor Work?

We’ll work with the water sensor (YF-S201), which features a water rotor and a hall effect sensor. Indeed, water flows through one end of this sensor and leaves through the other. 

Plus, when water flows through the sensor, it hits the water rotor and activates it. So, the speed of the water flow determines the speed of the rotor’s rotation.

For each successful rotation of the water rotor, the hall effect sensor produces a pulse via the signal output pin. 

Thus, the number of pulses on the signal output pin depends on the turbine’s rotational speed.

How? The water rotor has a magnet that helps the hall effect sensor detect the water flow. When water flows through the sensor, the speed affects the sensor’s magnetic flux

So, the hall effect sensor detects and generates an output proportional to the magnetic flux.

In other words, the water flow sensor generates a square wave for every rotation of the water rotor. 

Thus, we can measure the water flow rate by calculating the number of pulses generated per second or minute.

Additionally, you can display your measurements on a 16×2 LCD or a computer serial monitor.

Other Types of Water Sensors

In truth, each water flow sensor works differently. While most water sensors have water rotors that spin according to water flow, others have more complex working principles.

Paddlewheel Sensors

Paddlewheel water flow sensors are the most common and less-expensive water flow sensors you can find on the market. Plus, the rotor works perpendicular to the flow rate. Hence, the sensor will only make contact with a limited flow cross-section.

Positive Displacement Flow Sensors

Positive displacement flow sensors work when you don’t have a straight pipe. It also works when you can’t use the paddlewheel sensor—like measuring viscous liquids.

PDM sensors are the only flow measuring technology that can directly measure liquid volume. It works by capturing pockets of fluid between rotating components. These rotating components are usually in a high-precision chamber.

You can think of filling a cup with liquid and pouring out the contents. Then count how many times you fill the cup.
Also, the rotational velocity of the PDM sensors depends on the flow rate since the flow of liquid causes the rotation.

Magnetic Flow Sensors

Contrarily, the magnetic flow sensors don’t feature any moving parts. Instead, it works based on Faraday’s Law of Electromagnetic induction. 

According to this law, conductive liquids produce voltage through a magnetic field. Thus, the magnetic flow sensor generates a magnetic field for measurements rather than motors. It also channels the magnetic field into the liquid running through the line.

Hence, the faster the liquid flow rate, the more voltage the liquid generates. And it causes the voltage induced in this sensor to be proportional to the water movement.

However, magnetic sensors would only work for wastewater applications—or dirty liquids with conductive materials. Therefore, you can’t measure pure water with this sensor because it lacks atoms.

Ultrasonic Flow Sensors

The ultrasonic flow meters use sound waves to detect how fast a liquid flows through a pipe. Also, ultrasonic flow sensors work on the doppler effect. Hence, the sensor will detect a flow when there’s a frequency shift in the ultrasonic signal.
Additionally, you can use ultrasonic flow sensors for applications that damage standard flow meters. Such applications include slurries, wastewater, and other dirty fluid applications. These water sensors also measure the speed of liquids and estimate the volumetric flow using ultrasound.

Features and Specifications

  • Operational Voltage: 4.5 – 24 Volts
  • Normal Voltage:5 to 18 Volts
  • Maximum Current: 15 mA or 5V
  • Load Capacity: ≤10 mA Volts or 5V
  • Flow Rate Capacity: 1 -30 L/min
  • Electric Strength: 1250 V/min
  • Water Pressure Range: less than 1.75 MPa
  • Operational Temperature: less than 800C
  • Operational Fluid Temperature: less than 1200C
  • Humidity Range: 35% to 90% RH
  • Insulation Resistance: greater than 100 Mohms

How to Use Water Flow Sensors

Luckily, there is a more accessible and cost-effect way to use a water flow sensor. An l you have to interface it to a microcontroller—in this case, Arduino. 

As we mentioned earlier, we’ll need to count the output sensors to measure the flow rate of any liquid. A d, we can use Arduino’s interrupt pins for pulse detection.

Before we continue, here are the components you need for this project:

Arduino Microcontroller

YF-S201 Water flow sensor

Breadboard cables (x3)

Breadboards and cables

Breadboards and cables

How to Connect the Water Flow Sensor to an Arduino

We’ll use the digital I/O pin two as our interrupt capture pin for counting the pulses from the sensor. 

To make the connections, simply:

  • Connect the YF-S201 power supply pins of the water sensor (black and red wires) to the 5v and ground pin of the Arduino.
  • Then, connect the yellow output voltage wire to the digital I/O pin 2 of the Arduino.
  • Finally, upload your Arduino code to complete the connection. 

1 – Arduino Code

2- Arduino Code

3- Arduino Code

4- Arduino Code

5- Arduino Code

Final Words

Accuracy is vital if you want a proper water management system. We recommend using the YF-S201 water flow sensor for this project. 

Though there are various other water sensors, the YF-S201 is more cost-effective and produces accurate readings.

Don’t forget to test your code to see the correct output. If your connections don’t work, crosscheck your principles and make sure you connect all wires properly. Then consider changing your components.
If you have any questions, don’t hesitate to contact us.

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Emma Lu
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