16-04-2012, 01:40 PM
ELECTRONIC NOTICE BOARD WITH LED DOT MATRIX DISPLAY AND PS2 KEYBOARD INTERFACING FOR USER FRIENDLY MESSAGE ENTRY
ELECTRONIC NOTICE BOARD.docx (Size: 280.53 KB / Downloads: 176)
POWER SUPPLY:
The input to the circuit is applied from the regulated power supply. The a.c. input i.e., 230V from the mains supply is step down by the transformer to 12V and is fed to a rectifier. The output obtained from the rectifier is a pulsating d.c voltage. So in order to get a pure d.c voltage, the output voltage from the rectifier is fed to a filter to remove any a.c components present even after rectification. Now, this voltage is given to a voltage regulator to obtain a pure constant dc voltage.
Transformer:
Usually, DC voltages are required to operate various electronic equipment and these voltages are 5V, 9V or 12V. But these voltages cannot be obtained directly. Thus the a.c input available at the mains supply i.e., 230V is to be brought down to the required voltage level. This is done by a transformer. Thus, a step down transformer is employed to decrease the voltage to a required level.
Rectifier:
The output from the transformer is fed to the rectifier. It converts A.C. into pulsating D.C. The rectifier may be a half wave or a full wave rectifier. In this project, a bridge rectifier is used because of its merits like good stability and full wave rectification.
Filter:
Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage.
LED INTERFACING:
LED stands for Light Emitting Diode.
Microcontroller port pins cannot drive these LEDs as these require high currents to switch on. Thus the positive terminal of LED is directly connected to Vcc, power supply and the negative terminal is connected to port pin through a current limiting resistor.
Advanced RISC Architecture:
• 130 Powerful Instructions – Most Single-clock Cycle Execution
• 32 x 8 General Purpose Working Registers
• Fully Static Operation
• Up to 16 MIPS Throughput at 16 MHz
• On-chip 2-cycle Multiplier
RF MODULE:
The RF module, as the name suggests, operates at Radio Frequency. The corresponding frequency range varies between 30 kHz & 300 GHz. In this RF system, the digital data is represented as variations in the amplitude of carrier wave. This kind of modulation is known as Amplitude Shift Keying (ASK).
Applications:
• Schools
• Public utility
• Bus stations
• Railway stations
• parks
Result of the implementation:-
By implementation of these project we can display or scroll the message at college notice board ,rail way stations , bus display system