Hall Effect Tachometer - Rasberry Pi

gistfile1.txt

import time, datetime, sys
import RPi.GPIO as GPIO
sense_pin = 7
LED_pin = 36

GPIO.setmode(GPIO.BOARD)
GPIO.setup(sense_pin, GPIO.IN)
GPIO.setmode(LED_pin, GPIO.OUT)

last_time = time.time()
this_time = time.time()
RPM = 0

def EventsPerTime(channel):
    global RPM, this_time, last_time
    GPIO.output(LED_pin, True) # LED on
    this_time = time.time() # Get current real time
    RPM = (1/(this_time - last_time)) * 60 # Revs/min real time diff
    print('Current RPM = ', '{:7.1f}'.format(RPM)) # Instantaneous RPMs, not average
    last_time = this_time # Store current time for next measurement; Requires multiple, contigious interrupts

    GPIO.output(LED_pin, False) # LED off (flash when reading)

    return()

# Interrupt: on input change, run EventsPerTime function
GPIO.add_event_detect(sense_pin, GPIO.RISING, callback=EventsPerTime, bouncetime=1)

# MAIN ROUTINE
timedate = datetime.datetime.now().strftime('%H:%M %Y%m%d %a')
print('System active @ ', timedate)
print('Ctrl-c to quit')
try:
    for x in range(0, 1200): # Loop x times
        time.sleep(0.5) # Time delay before looping
    
except:
    time.sleep(2) # Allow settling before quitting
    GPIO.output(LED_pin, False)
    GPIO.remove_event_detect(sense_pin)
    GPIO.cleanup()
    print('Done')