The article discusses how to make a simple laser communicator circuit for sending and receiving data through laser beam.
By Girish Radhakrishnan
Laser has been a boon since its invention. Laser is used in wide variety of applications, from Blu-ray driver to high powered cutting torch. There are also many classifications of laser technologies.
Here we use them for communication and receive an audio signal at the receiver.
Laser technology is used in satellite communication system, optic fiber communication system etc. The principle behind laser communication is series of pluses applied at transmitter and decoding the pulses at receiver end. This article explains how to make one at your hobby lab.
The Transmitter Circuit
The Receiver Circuit
The Circuit Design:
The setup consists of two parts, a transmitter and a receiver. The transmitter converts the audio signal to pulsating light with respect to input.
The receiver is an amplifier paired with a solar cell as photo detector. Due to pulsating light input to the receiver the voltage across the solar cell varies with respect to audio input.
However we won’t see pulsating light, we only see static illumination of laser beam. This faint signal is picked up by an amplifier.
The receiver consists of single transistor amplifier with laser module. C1 is DC current blocking capacitor, R1 and R2 gives necessary bias for the transistor.
R3 is current limiting resistor; you may adjust the value of this resistor to get right amount of current flow and brightness for your laser.
Checking Laser Diode Specifications
If you purchase a laser module from online or retail store or anywhere, please check the data sheet or specification for your laser module. If you violate those specifications you may damage your laser module. Please adjust R3 and input voltage according to the specifications.
Don't use laser modules from DVD writer or any laser rated class 3B. They shoot high power laser beam which could damage your solar cell and not safe for your eyes and skin.
You may use toy laser or laser pointer that has 3 button cells. These lasers are commonly available at stationary stores.
You may use any amplifier lying around your house which has good sensitivity. It is not mandatory to use the same amplifier illustrated here. The audio source may be from your Smartphone, MP3 player, iPod etc.
To test this simple laser communicator circuit go to a room where electrical lights are switch off, if you don’t you will hear humming noise on your amplifier. Power up both the transmitter and receiver, input the audio signal to transmitter and direct the laser beam to solar cell, you will hear clear sound at speaker.
You may use active high pass filter to filter out the humming noise at receiver. This circuit is capable of carrying transmitted signal around 100 meters depending how powerful your laser beam is.