Using the HC-SR04 ultrasonic receiver

[fotoartist78]

Has anyone used the Sensor mentioned in topic header? If so could they make the code they used to pulse & activate it that was used available to me through this forum, I would be very grateful.

[joan]

What is wrong with the many solutions offered when you google "raspberry pi sr04"?

[fotoartist78]

Many thanks 'Joan' for your suggestion , I have not tried that so I will do that and hope to find something useful.

[joan]

In your other post you mentioned the Arduino Uno.

Software used on the Pi won't be optimal on an Arduino (strangely enough most of the poor Pi software for the HC-SR04 was ported from a good Arduino solution without considering the differences between the platforms).

[pcmanbob]

Here is some commented code that explains how it works.

it was written for python but could be simply changed to run with python3

Code: Select all

#!/usr/bin/python


# Import required Python libraries
import time
import RPi.GPIO as GPIO

# Use BCM GPIO references
# instead of physical pin numbers
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)

# Define GPIO to use on Pi
GPIO_TRIGGER = 23
GPIO_ECHO    = 24



# Set pins as output and input
GPIO.setup(GPIO_TRIGGER,GPIO.OUT)  # Trigger
GPIO.setup(GPIO_ECHO,GPIO.IN)      # Echo

# Set trigger to False (Low)
GPIO.output(GPIO_TRIGGER, False)

print "Ultrasonic Measurement"

# Allow module to settle
time.sleep(0.5)

# Send 10us pulse to trigger
GPIO.output(GPIO_TRIGGER, True)
time.sleep(0.00001)
GPIO.output(GPIO_TRIGGER, False)
start = time.time()

while GPIO.input(GPIO_ECHO)==0:
  start = time.time()

while GPIO.input(GPIO_ECHO)==1:
  stop = time.time()

# Calculate pulse length
elapsed = stop-start

# Distance pulse travelled in that time is time
# multiplied by the speed of sound (cm/s)
distancet = elapsed * 34300

# That was the distance there and back so halve the value
distance = distancet / 2

print "Distance :", distance

# Reset GPIO settings
GPIO.cleanup()

One other thing you should be aware of is if you are using a 5v HC-SR04 then you need to reduce the echo pin voltage before connecting it to you pi gpio.

like this

[JustSayingHi!]

Which resistors should I use for the HC-SR04 ultrasonic sensor?

[pcmanbob]

As shown in my diagram a 1K ohm and 2K ohm , even the 1/8 W power rated ones will be fine.

[rpiMike]

The two while loops in that code need timeouts - they could cause the code to hang. Looks like code ported from Arduino.