I need to connect 4 water flow sensors to an arduino uno r3 and send their readings to a WebService. The problem is : They work using interrupts and arduino uno just has support to 2 interrupts.
I've been searching for a answer to this problem for a few months and came to this possible solutions :
Use 2 arduino's
Use multiinterrupt pin code
Create an additional board.
But none of these solutions are showing interesting , here are the whys :
Use 2 arduino's : Too expensive and some reading are being lost
MultiInterrupt pin Code : i got some delay to read all the sensors (from 1 second to 2 seconds)
Create an additional board : Thats the most interesting idea till now . The idea is create a board with 4 registers , the sensors will input their interruptions in the registers (1 register per sensor) and arduino will be pulling through the registers reading and reseting its contents.
But i feel that i'm far from a concrete answer. Did anyone of you guys have been through this before or can help me with some tip?
Are you saying that each flow meter produces a max of 15 pulses per second i.e. 60 pulses for all 4 meters?
OR, are you saying that all 4 together produce 15 pulses per second
In that context, I don't understand "Thus, in a looping with 10 executions (10 seconds) must have 10 readings" I imagine you would expect 150 or 600 readings in 10 seconds - not 10 readings.
You should be able to take 600 readings in 1 second without using interrupts.
I don't know what you mean by "the routine execution". Your code should be organized so that the loop() function repeats hundreds or thousands of times per second.
I use the interruption to increase a variable and at the end of one second get the flow.
All codes that I found for this sensor used interruption. I do not know if there is another way to do it, is there?
Robin2:
Are you saying that each flow meter produces a max of 15 pulses per second i.e. 60 pulses for all 4 meters?
OR, are you saying that all 4 together produce 15 pulses per second
In that context, I don't understand "Thus, in a looping with 10 executions (10 seconds) must have 10 readings" I imagine you would expect 150 or 600 readings in 10 seconds - not 10 readings.
You should be able to take 600 readings in 1 second without using interrupts.
I don't know what you mean by "the routine execution". Your code should be organized so that the loop() function repeats hundreds or thousands of times per second.
/*
Liquid flow rate sensor -DIYhacking.com Arvind Sanjeev
Measure the liquid/water flow rate using this code.
Connect Vcc and Gnd of sensor to arduino, and the
signal line to arduino digital pin 2.
*/
byte statusLed = 13;
byte sensorInterrupt = 0; // 0 = digital pin 2
byte sensorPin = 2;
// The hall-effect flow sensor outputs approximately 4.5 pulses per second per
// litre/minute of flow.
float calibrationFactor = 4.5;
volatile byte pulseCount;
float flowRate;
unsigned int flowMilliLitres;
unsigned long totalMilliLitres;
unsigned long oldTime;
void setup()
{
// Initialize a serial connection for reporting values to the host
Serial.begin(9600);
// Set up the status LED line as an output
pinMode(statusLed, OUTPUT);
digitalWrite(statusLed, HIGH); // We have an active-low LED attached
pinMode(sensorPin, INPUT);
digitalWrite(sensorPin, HIGH);
pulseCount = 0;
flowRate = 0.0;
flowMilliLitres = 0;
totalMilliLitres = 0;
oldTime = 0;
// 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);
}
/**
* Main program loop
*/
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
detachInterrupt(sensorInterrupt);
// 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(int(flowRate)); // Print the integer part of the variable
Serial.print("."); // Print the decimal point
// Determine the fractional part. The 10 multiplier gives us 1 decimal place.
frac = (flowRate - int(flowRate)) * 10;
Serial.print(frac, DEC) ; // Print the fractional part of the variable
Serial.print("L/min");
// Print the number of litres flowed in this second
Serial.print(" Current Liquid Flowing: "); // Output separator
Serial.print(flowMilliLitres);
Serial.print("mL/Sec");
// Print the cumulative total of litres flowed since starting
Serial.print(" Output Liquid Quantity: "); // Output separator
Serial.print(totalMilliLitres);
Serial.println("mL");
// 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
pulseCount++;
}
Robin2:
I now understand that each sensor produces 15 pulses but I don't undertand why you consider 15 pulses to be a single reading.
In my mind if the flow rate is lower there will be fewer pulses per second (I am assuming 15 corresponds with the maximum flow rate).
...R
As you can see in the sketch above , i use the 15 pulses (registered in the pulseCount variable) to calculate the flow of that second. And in the end that is what matters to me , because i'll send the flow to the WebService.
I can't make sense of the code in Reply #13. Please modify the Reply and use the code button </> so your code looks like this and is easy to copy to a text editor.
It sounds to me as if you are counting the number of pulses in a second and using that to calculate the flow rate. That is perfectly reasonable but you won't always get 15 pulses in a second.
It crossed my mind during the night that you could, perhaps, use the 2 external interrupts for 2 of the flow meters and use 2 pin-change interrupts for the other 2 meters. If you have each pin-change interrupt on a different port (hence triggering a different interrupt) you would not need code to figure out which pin the interrupt was on. However the trouble with pin-change interrupts is that they are triggered by highs and lows. I guess you could arrange the external interrupts as CHANGE also and then everything would be registering 2-times the number of pulses.
Robin2:
I can't make sense of the code in Reply #13. Please modify the Reply and use the code button </>
so your code looks like this
and is easy to copy to a text editor.
It sounds to me as if you are counting the number of pulses in a second and using that to calculate the flow rate. That is perfectly reasonable but you won't always get 15 pulses in a second.
I edited the # reply and... Thats it !! you got it ! yes , i won't get always 15 pulses in a second (thats the maximum pulses i can get).
Robin2:
It crossed my mind during the night that you could, perhaps, use the 2 external interrupts for 2 of the flow meters and use 2 pin-change interrupts for the other 2 meters. If you have each pin-change interrupt on a different port (hence triggering a different interrupt) you would not need code to figure out which pin the interrupt was on. However the trouble with pin-change interrupts is that they are triggered by highs and lows. I guess you could arrange the external interrupts as CHANGE also and then everything would be registering 2-times the number of pulses.
...R
Thats interesting ! I'll give it a try !
So to be clear to me , the external interrupts are activated by the comand attachInterrupt()
and the pin-change interrupts can be like this PinChangeInterrupt ,right?
