Lesson 5 Laser Emitter Module

Introduction

Laser is widely used in medical treatment, military, and other fields due to its good directivity and energy concentration.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

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

– 1 * Laser Emitter module

– 1 * 2-Pin anti-reverse cable

Experimental Principle

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Lasers differ from other sources of light because they emit light coherently.

Spatial coherence allows a laser to be focused to a tight spot, enabling applications like laser cutting and lithography, and a laser beam to stay narrow over long distances (collimation), enabling applications like laser pointers. Lasers can also have high temporal coherence which allows them to have a very narrow spectrum, i.e., they only emit light of a single color. And its temporal coherence can be used to produce pulses of light—as short as a femtosecond.

The schematic diagram:

Experimental Procedures

Step 1: Build the circuit

Raspberry Pi	Laser Emitter Module
5V	VCC
GPIO0	SIG

For C language users:

Step 2: Change directory

 cd /home/pi/SunFounder_SensorKit_for_RPi2/C/05_laser/

Step 3: Compile

gcc laser.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 05_laser.py

Now you can see the module send out Morse signals.

Note: Do NOT look directly at the laser head. It can cause great harm to your eyes. You can point the laser beam to the table and see the light spot flashing on the table.

C Code

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

#define LaserPin    0

int main(void)
{
	if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
		printf("setup wiringPi failed !");
		return 1; 
	}
	//printf("linker LedPin : GPIO %d(wiringPi pin)\n",LedPin); //when initialize wiring successfully,print message to screen

	pinMode(LaserPin, OUTPUT);

	while(1){
		digitalWrite(LaserPin, HIGH);
		delay(500);
		digitalWrite(LaserPin, LOW);
		delay(500);
	}

	return 0;
}

Python Code

#!/usr/bin/env python
#####################################################
#
#	DO NOT WATCH THE LASER DERECTELY IN THE EYE!
#
#####################################################
import RPi.GPIO as GPIO
import time

LedPin = 11    # pin11

def setup():
	GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
	GPIO.setup(LedPin, GPIO.OUT)   # Set LedPin's mode is output
	GPIO.output(LedPin, GPIO.HIGH) # Set LedPin high(+3.3V) to off led

def loop():
	while True:
		print '...Laser on'
		GPIO.output(LedPin, GPIO.LOW)  # led on
		time.sleep(0.5)
		print 'Laser off...'
		GPIO.output(LedPin, GPIO.HIGH) # led off
		time.sleep(0.5)

def destroy():
	GPIO.output(LedPin, GPIO.HIGH)     # led off
	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()