I want to know if it is possible to put a boundary or limit to the volume that passes through a water flow sensor, and close the pipe using a solenoid valve.

Example: I only want 400 ml of water to pass, so when the water flow sensor reads how much water has passed in the pipe, if 400 is reached, the solenoid will close the pipe.

Sorry for my bad English, it is not my first language. I'm hopping that someone can help me out.

  • A snippet of code please .. And a explanation Mar 30, 2017 at 5:37
  • The time that your solenoid is open, could also be an indication of the amount of water passed.
    – Paul
    Mar 30, 2017 at 6:01
  • 1
    Have you asked the manufacturer of the water flow sensor how it works? What have you tried yourself? What model numbers do these sensors/actuators have? Have you actually tried something? There is no way that we can/will provide code for a project that we do not know the details or issues of...
    – Paul
    Mar 30, 2017 at 6:03
  • I try some codes i find in the internet here bc-robotics.com/tutorials/using-a-flow-sensor-with-arduino and the brand and model of my water flow sensor is sea model yf s201 .. i dont have any idea on how to achieve that or to be able to put limit . Mar 30, 2017 at 6:55

2 Answers 2


hello @kaisar Great you have not mentioned which flow sensor are you using. I am assuming that you are using flow sensor YF-S201 or YF-S401(Hall Effect).You have to do Little calculation for measuring water flow. In order to measure the quantity of water being passed in particular time through the water flow sensor it was first passed through the water flow sensor which was taken as input interface in the flow. Formulas are applied in order to measure the number of rotations/pulses in a minute of rotation.

Here I have determined flow rate by change in velocity of water. Velocity depends on the pressure that forces the through pipelines. As the pipe’s cross-sectional area is known and remains constant, the average velocity is an indication of the flow rate. The basis relationship for determining the liquid’s flow rate in such cases is

Q=VxA, where Q is flow rate/total flow of water through the pipe, V is average velocity of the flow and A is the cross-sectional area of the pipe

Calibration Factor = The hall-effect flow sensor outputs pulses per second per litre/minute of flow.(check your datasheet) here I have taken 4.5.

Flow Rate(litres/minute) = ((1000.0 / Total time) x Pulse Count) / calibration Factor

Flow Rate(MilliLitres/Second) = (Flow Rate / 60) x 1000

There you have to calculate the total water flow in a given time by adding flow rate for each second. There after you have check your set point value(400ml)..if condition satisfied you you can turn off your Solenoid valve.

and the code is

int sensorInterrupt = 0;  // interrupt 0
int sensorPin       = 2; //Digital Pin 2
int solenoidValve = 5; // Digital pin 5
unsigned int SetPoint = 400; //400 milileter

/*The hall-effect flow sensor outputs pulses per second per litre/minute of flow.*/
float calibrationFactor = 4.5; //You can change according to your datasheet

volatile byte pulseCount =0;  

float flowRate = 0.0;
unsigned int flowMilliLitres =0;
unsigned long totalMilliLitres = 0;

unsigned long oldTime = 0;

void setup()
  // Initialize a serial connection for reporting values to the host
  pinMode(solenoidValve , OUTPUT);
  pinMode(sensorPin, INPUT);
  digitalWrite(sensorPin, HIGH);

  /*The Hall-effect sensor is connected to pin 2 which uses interrupt 0. Configured to trigger on a FALLING state change (transition from HIGH
  (state to LOW state)*/
  attachInterrupt(sensorInterrupt, pulseCounter, FALLING); //you can use Rising or Falling

void loop()
   if((millis() - oldTime) > 1000)    // Only process counters once per second
    // Disable the interrupt while calculating flow rate and sending the value to the host
    // Because this loop may not complete in exactly 1 second intervals we calculate the number of milliseconds that have passed since the last execution and use that to scale the output. We also apply the calibrationFactor to scale the output based on the number of pulses per second per units of measure (litres/minute in this case) coming from the sensor.
    flowRate = ((1000.0 / (millis() - oldTime)) * pulseCount) / calibrationFactor;
    // Note the time this processing pass was executed. Note that because we've
    // disabled interrupts the millis() function won't actually be incrementing right
    // at this point, but it will still return the value it was set to just before
    // interrupts went away.
    oldTime = millis();
    // Divide the flow rate in litres/minute by 60 to determine how many litres have
    // passed through the sensor in this 1 second interval, then multiply by 1000 to
    // convert to millilitres.
    flowMilliLitres = (flowRate / 60) * 1000;
    // Add the millilitres passed in this second to the cumulative total
    totalMilliLitres += flowMilliLitres;
    unsigned int frac;
    // Print the flow rate for this second in litres / minute
    Serial.print("Flow rate: ");
    Serial.print(flowMilliLitres, DEC);  // Print the integer part of the variable

    // Print the cumulative total of litres flowed since starting
    Serial.print("Output Liquid Quantity: ");        
    If (totalMilliLitres =< 400)

// Reset the pulse counter so we can start incrementing again
    pulseCount = 0;
    // Enable the interrupt again now that we've finished sending output
    attachInterrupt(sensorInterrupt, pulseCounter, FALLING);

//Insterrupt Service Routine

void pulseCounter()
  // Increment the pulse counter

void SetSolinoidValveON()
  digitalWrite(solenoidValve, HIGH);
void SetSolinoidValveOFF()
  digitalWrite(solenoidValve, LOW);
  • What is the difference between RISING and FALLING in this line of code attachInterrupt(sensorInterrupt, pulseCounter, FALLING); Mar 30, 2017 at 12:22
  • Actually working principle of this flow sensor is its produce pulses(Square Wave) proportional to flow rate of liquid. When a circuit is rising edge-triggered, it becomes active when its clock signal goes from low to high, and ignores the high-to-low transition. A falling edge is the high to low transition. Mar 31, 2017 at 4:29
  • I try this code and it doesn't work , totalMilliLitres stores total liters flowed since starting and it will close the solenoid once . Mar 31, 2017 at 14:13
  • You have to first modify this code according to your flow sensor datasheet otherwise its gives erroneous result cause parameters are assumed based which I given in this code so it will not match with your flow meter datasheet. anyway upload your skech and output along with your flow sensor datasheet Apr 1, 2017 at 4:28

Using a YF201 you cannot measure less than 1 litre / minute or more than 30 l/m. (ref http://www.bc-robotics.com/tutorials/using-a-flow-sensor-with-arduino/)

The device sends a pulse for every 2.25ml that flows through it. All you needs to do is take the amount you want to let through (400ml) and divide that by 2.25ml and you get 177.8 pulses. So once your Arduino counts 178 pulses then you trigger the valve to close.

Its not going to be very accurate, because unless the valve closes instantly there will be a bit of an overshoot. and you have to measure in units of 2.25ml.

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