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# Counting Pulses

The Expander Pi is an Analogue, Digital and RTC development Interface for the Raspberry Pi

887 Views - Created 31/08/2020

31/08/2020

Posted by:
harvey

Wondering if anyone knows there is any sample projects where someone has demonstrated counting pulses? I have a water flow device, purchased on Amazon ( https://www.amazon.com/dp/B07DLZH8P2/ref=dp_prsubs_1 ). Wondering what the simplest way to connect this to my project which when done will include monitoring temperature and pressure in addition to water flow.

On a side note, my son and I created a really nice temperature monitoring sample. We included calibrating a thermistor and plotting a graph that shows the curve of the voltage to temperature values are correct. We used a LittleFuse p/n USP 10978 and applied the Steinhart–Hart equation to prove our tests were accurate. Is this something I can post here for other users that might be trying to create a similar project?

Best,
Harvey

31/08/2020

Posted by:
andrew

Hello Harvey

The code below shows a simple counter program that will increment a counter variable every time pin 1 on the digital IO bus is pulled high to 5V.

``from __future__ import absolute_import, division, print_function, \                                                    unicode_literalsimport timetry:    import ExpanderPiexcept ImportError:    print("Failed to import ExpanderPi from python system path")    print("Importing from parent folder instead")    try:        import sys        sys.path.append('..')        import ExpanderPi    except ImportError:        raise ImportError(            "Failed to import library from parent folder")def main():    '''    Main program function    '''    # Create an instance of the IO class called iobus.    iobus = ExpanderPi.IO()    # Create a counter variable    counter = 0    # Set all pins on the IO port A to be inputs with internal pull-ups disabled.    iobus.set_port_pullups(0, 0x00)    iobus.set_port_direction(0, 0xFF)    while True:        if (iobus.read_pin(1) == 1):                        counter += 1  # increment counter            # wait for pin to go low again            while (iobus.read_pin(1)):                # sleep 200ms before checking the pin again                time.sleep(0.2)            # print the counter value to screen            print("Count: " + str(counter))if __name__ == "__main__":    main()``

You may need to add a 10K resistor between pin 1 and ground to pull the pin low between pulses, otherwise, it could be left in a floating state where it may cause false triggers.

Depending on how fast your flowmeter pulses you may need to decrease the time.sleep(0.2) value inside the while loop to allow more than 5 pulses per second.

You are welcome to post your temperature monitoring sample on this forum, I am sure other forum users will find it useful.

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