Lesson 25 Ultrasonic Ranging Module

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Introduction

The ultrasonic sensor uses sound to accurately detect objects and measure distances. It sends out ultrasonic waves and converts them into electronic signals.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

– 1 * Network cable (or USB wireless network adapter)

– 1 * Ultrasonic ranging module

– Several jumper wires (M to F)

Experimental Principle

This sensor works by sending a sound wave out and calculating the time it takes for the sound wave to get back to the ultrasonic sensor. By doing this, it can tell us how far away objects are relative to the ultrasonic sensor.

Test distance = (high level time * velocity of sound (340M/S)) / 2 (in meters)

Experimental Procedures

Step 1: Build the circuit

Raspberry Pi	Ultrasonic Ranging Module
5V	VCC
GPIO0	Trig
GPIO1	Echo
GND	GND

For C language users:

Step 2: Change directory

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/25_ultrasonic_ranging/

Step 3: Compile

gcc ultrasonic_ranging.c -lwiringPi

Step 4: Run

sudo ./a.out

For Python users:

Step 2: Change directory

cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run

sudo python 25_ultrasonic_ranging.py

Now you can see the distance between the ultrasonic ranging module and the obstacle in front on the screen. Sway your hand over the ultrasonic ranging module slowly and observe the distance printed on the screen.

C Code

/*******************************
* Ultra Sonic Raning module Pin VCC should
* be connected to 5V power.
******************************/
#include <wiringPi.h>
#include <stdio.h>
#include <sys/time.h>#define Trig 0
#define Echo 1void ultraInit(void)
{
pinMode(Echo, INPUT);
pinMode(Trig, OUTPUT);
}float disMeasure(void)
{
struct timeval tv1;
struct timeval tv2;
long time1, time2;
float dis;digitalWrite(Trig, LOW);
delayMicroseconds(2);digitalWrite(Trig, HIGH);
delayMicroseconds(10); //send out ultrasonic pulses
digitalWrite(Trig, LOW);

while(!(digitalRead(Echo) == 1));
gettimeofday(&tv1, NULL); //get current timewhile(!(digitalRead(Echo) == 0));
gettimeofday(&tv2, NULL); //get current timetime1 = tv1.tv_sec * 1000000 + tv1.tv_usec; //microsecond time
time2 = tv2.tv_sec * 1000000 + tv2.tv_usec;dis = (float)(time2 – time1) / 1000000 * 34000 / 2; //calculate the distancereturn dis;
}int main(void)
{
float dis;if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
printf(“setup wiringPi failed !”);
return 1;
}ultraInit();

while(1){
dis = disMeasure();
printf(“%0.2f cm\n\n”,dis);
delay(300);
}return 0;
}

Python Code

#!/usr/bin/env pythonimport RPi.GPIO as GPIO
import timeTRIG = 11
ECHO = 12def setup():
GPIO.setmode(GPIO.BOARD)
GPIO.setup(TRIG, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)def distance():
GPIO.output(TRIG, 0)
time.sleep(0.000002)GPIO.output(TRIG, 1)
time.sleep(0.00001)
GPIO.output(TRIG, 0)
while GPIO.input(ECHO) == 0:
a = 0
time1 = time.time()
while GPIO.input(ECHO) == 1:
a = 1
time2 = time.time()during = time2 – time1
return during * 340 / 2 * 100def loop():
while True:
dis = distance()
print dis, ‘cm’
print ”
time.sleep(0.3)def destroy():
GPIO.cleanup()if __name__ == “__main__”:
setup()
try:
loop()
except KeyboardInterrupt:
destroy()