What you need:
* 2 X pieces of wood 4X6. 1/4'' and the other 1/2'' thick
* 1 X 3 inches pipe. length varies depending of the deep of your pit.
* A couple of screw
* 1 X 1k resistor
* 1 X Raspberry pi
* 1X HC-SR04 ultrasonic sensor
Step 1: The Sensor
Step 2: Create the Base
Step 3: Prepare the Base for the Sensor.
Step 4: Add the Sensor
Step 6: Connection
Pin 1 GND: connect to the ground of the rasp.
Pin 2 Echo to gpio 9
Pin 3 Trig to gpio 11. Add a 1k resistor
Pin 4 VCC to the 3.3V
Note 1: According to the manual, the sensor used 5v. But it work perfectly at 3.3v.
Note 2: Beware, we see the back of the sensor in this pic, so the order of the pin are reverse.
Step 7: Add the Pipe
Step 8: The Code
# Measure distance using an ultrasonic module
# Author : Matt Hawkins
# Date : 09/01/2013
# Import required Python libraries
import RPi.GPIO as GPIO
# Use BCM GPIO references
# instead of physical pin numbers
# Define GPIO to use on Pi
GPIO_TRIGGER = 11
GPIO_ECHO = 9
# You need to change the variable "compensation" according to the distance from the edge of the pit to the sensor
compensation = -11
print "Ultrasonic Measurement"
# 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)
# Allow module to settle
# Send 10us pulse to trigger
start = time.time()
start = time.time()
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)
distance = elapsed * 34000
# That was the distance there and back so halve the value
distance = distance / 2
distance = distance + compensation
print "Distance : %.1f" % distance
# Reset GPIO settings
Note: You need to change the variable "compensation" according to the distance from the edge of the pit to the sensor
Note 2: The distance are in cm.
Thank to Matt Hawkins for this code
Step 9: Final Result
Step 10: Next Tutorial
I'm not as good as I want to in english, so feel free to send me any correction in my text.