Abstract:
The aim of this work is to design and implement a circuit that can be
switched by infrared laser (IR) source. The function of IR laser is to carry
the binary coded control signal to a receiver location at which the received
signal can detected and processed. To achieve this goal a transmitter and
receiver circuits have been designed and implemented.
At the transmitter circuit, IR laser diode with output power of 10 mW
and wavelength of 808nm has been modulated using binary code. A binary
code uses two possible states, 0 or 1 to transmit an optical signal. Thus
transmitted optical message using a binary code would consist of bits
sequence of 0's and 1's s .Specifically 0s would be transmitted when the
light source was turned off. The 1s would be transmitted when the light
source was turned on.
At the receiver circuit the original signal has been detected by
photodetector, converted to voltage and amplified. Then this signal was
applied to the clock input of asynchronous counter, that counts from 0 up to
255(00000000-11111111).The counter outputs were connected to EPROM
inputs. The EPROM was programmed to operate such light emitting
diode(LED) of the eight LEDs connected to its output terminals ,when a
particular counts were received .According to this work, the designed and
implemented circuit has been operated efficiently and a good performance
was obtained, and the shapes resulted from experimental work are clear and
have a good resolution .The key parameters of operation of these loads are
the pulse width and pattern of the written program in the E-prom., so in this
fashion each one of the eight LEDs has been operated for a predetermined
length of time according to the received counts.
