Ultrasonic sensor stops working a few minutes later

Question

I want to get distance continuously using while loop but a few minutes later my code suddenly stops working and doesn't get distance (there is None value in distance variable) I have changed first time.sleep(0.01) to time.sleep(1) and to other seconds but It is still same with others.

I am using RPi 3 b+, Raspbian, Python3, HC-SR04 and 1K, 2K resistors.

I connect ultrasonic sensor to RPi using this tutorial from MODMYPI: HC-SR04 Ultrasonic Range Sensor on the Raspberry Pi

and here is my code:

import RPi.GPIO as GPIO
import time

try:
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)

    TRIG = 23
    ECHO = 24

    while True:
        GPIO.setup(TRIG,GPIO.OUT)
        GPIO.setup(ECHO,GPIO.IN)

        GPIO.output(TRIG,False)

        time.sleep(0.01)

        GPIO.output(TRIG,True)

        time.sleep(0.00001)

        GPIO.output(TRIG,False)

        while GPIO.input(ECHO) == 0:
            pulse_start = time.time()

        while GPIO.input(ECHO) == 1:
            pulse_end = time.time()

        pulse_duration = pulse_end - pulse_start
        distance = pulse_duration * 17000
        distance = round(distance, 2)

        print(distance)
except:
    GPIO.cleanup()

Answer 1

I would suggest 2 changes. Firstly it is possible that the program can get stuck in the while loops so add a timeout. Secondly initialise the pulse_start and pulse_end variables incase the while loops don't get entered. This could be improved to ignore results where the timeout has been used.

import RPi.GPIO as GPIO
import time

try:
    GPIO.setmode(GPIO.BCM)
    GPIO.setwarnings(False)

    TRIG = 23
    ECHO = 24
    maxTime = 0.04

    while True:
        GPIO.setup(TRIG,GPIO.OUT)
        GPIO.setup(ECHO,GPIO.IN)

        GPIO.output(TRIG,False)

        time.sleep(0.01)

        GPIO.output(TRIG,True)

        time.sleep(0.00001)

        GPIO.output(TRIG,False)

        pulse_start = time.time()
        timeout = pulse_start + maxTime
        while GPIO.input(ECHO) == 0 and pulse_start < timeout:
            pulse_start = time.time()

        pulse_end = time.time()
        timeout = pulse_end + maxTime
        while GPIO.input(ECHO) == 1 and pulse_end < timeout:
            pulse_end = time.time()

        pulse_duration = pulse_end - pulse_start
        distance = pulse_duration * 17000
        distance = round(distance, 2)

        print(distance)
except:
    GPIO.cleanup()