27-05-2014, 11:18 AM
PC to PC communication through laser ABSTRACT
ABSTRACT
The project consists of the design of the circuits for LASER link communication. The circuit has
been developed for data and audio (voice) transmission separately. Since, the LASER is a highly
directed beam with LOS (Line Of Sight) communication, hence it is required that transmitting
and receiving elements be aligned in a proper axis. Our project utilizes software controlled
UART protocol and the simplex type of communication. The project consists of two distinct
circuits for audio and data transmissions. In data communication, the transmitter consists of the
main controlling element, i.e. ATMEL AT89C52 microcontroller which interfaces the keypad
and LCD for input and output purposes.
The data is transmitted by using ON-OFF keying. The receiver is the photo diode which is
sensitive in the region of red light in the visible spectrum. The photodiode is interfaced with
another ATMEL AT89C52 to recognize the character by identifying the corresponding ASCII
value and then displayed in the LCD module interfaced with the receiving microcontroller.
For the audio transmission purposes, the input is taken from the microphone and low voltage
audio signal is amplified using the amplifying and conditioning circuit such that output voltage
reaches to 3-3.5V. The audio signal does the amplitude modulation and the information is
transmitted by varying of intensity of laser beam. The photodiode receives the varying intensity
of light and converts them to corresponding voltages. It is then interfaced with the conditioning
circuits and the speaker is used to output the audio signal which is interfaced with the 3.5 mm
jack.
A laser diode of Class IIIA having effective wavelength in the range 630 nm to 680 nm which is
readily available in the market is implemented for communication purposes.