Lesson 29 IR Obstacle Avoidance Module

Introduction

An IR obstacle avoidance module (as shown below) uses infrared reflection principle to detect obstacles. When there is no object ahead, infrared-receiver cannot receive signals; when there is an object ahead, it will block and reflect infrared light, then infrared-receiver can receive signals.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

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

– 1 * IR Obstacle module

– 1 * 3-Pin anti-reverse cable

Experimental Principle

An obstacle avoidance sensor mainly consists of an infrared-transmitter, an infrared-receiver and a potentiometer. According to the reflecting feature of an object, if there is no obstacle, emitted infrared ray will weaken with the propagation distance and finally disappear. If there is an obstacle, when infrared ray encounters an obstacle, it will be reflected back to the infrared-receiver. Then the infrared-receiver detects this signal and confirms an obstacle exists ahead.

Note: The detection distance of the infrared sensor is adjustable – you may adjust it by the potentiometer.

The schematic diagram:

Experimental Procedures

Step 1: Build the circuit

Raspberry Pi	IR Obstacle Module
GPIO0	SIG
5V	VCC
GND	GND

For C language users:

Step 2: Change directory

cd /home/pi/SunFounder_SensorKit_for_RPi2/C/29_ir_obstacle/

Step 3: Compile

gcc ir_obstacle.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 29_ir_obstacle.py

Now, if there is an obstacle ahead, a string “Detected Barrier!” will be printed on the screen.

 C Code

#include <wiringPi.h>
#include <stdio.h>

#define ObstaclePin      0

void myISR(void)
{
	printf("Detected Barrier !\n");
}

int main(void)
{
	if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
		printf("setup wiringPi failed !\n");
		return 1; 
	}
	
	if(wiringPiISR(ObstaclePin, INT_EDGE_FALLING, &myISR) < 0){
		printf("Unable to setup ISR !!!\n");
		return 1;
	}
	
	while(1){
		;
	}

	return 0;
}

Python Code

#!/usr/bin/env python
import RPi.GPIO as GPIO

ObstaclePin = 11

def setup():
	GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
	GPIO.setup(ObstaclePin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def loop():
	while True:
		if (0 == GPIO.input(ObstaclePin)):
			print "Detected Barrier!"
			

def destroy():
	GPIO.cleanup()                     # Release resource

if __name__ == '__main__':     # Program start from here
	setup()
	try:
		loop()
	except KeyboardInterrupt:  # When 'Ctrl+C' is pressed, the child program destroy() will be  executed.
		destroy()