1. PRE-PROGRAMMED DIGITAL SCROLLING MESSAGE
Under the guidance of
submitted by

2. contents PROJECT OVERVIEW BLOCK DIAGRAM MICROCONTROLLER 8052
ALPHA NUMERIC KEYS
74LS138
BC557
SCHEMATIC & WORKING OF THE PROJECTS
ADVANTAGES
APPLICATIONS
FUTURE SCOPE
CONCLUSION

3. Project overview
A DC voltage of 5V is drawn from power supply voltage regulator is fed to micro controller.
Here the circuit uses 16 segment alpha numeric displays to show 16 characters at a time.
More over, programming has been done in micro controller to make the characters move in a beautiful manner.
It displays 16 different messages to depict different occasions, which can be selected by the user through a DIP Switch.
Using of Alphanumeric displays for above purpose, programming burden is reduced and becomes highly cost effective.
This circuit is mainly used in areas like railway platforms,banks,hotels,nightclubs etc

4. Block diagram

5. Microcontroller It is a smaller computer
Has on-chip RAM, ROM, I/O ports...
RAM
ROM
I/O Port
Timer
Serial COM Port
Microcontroller
CPU
A single chip

6. Features of MC 8052
8K Bytes of In-System Programmable (ISP) Flash Memory
4.0V to 5.5V Operating Range
Fully Static Operation: 0 Hz to 33 MHz
256 x 8-bit Internal RAM
32 Programmable I/O Lines
Three 16-bit Timer/Counters
Eight Interrupt Sources
Full Duplex UART Serial Channel

7. Block diagram of MC CPU On-chip RAM On-chip ROM for program code
4 I/O Ports
Timer 0
Serial Port
OSC
Interrupt Control
External interrupts
Timer 1
Timer/Counter
Bus Control
TxD RxD
P0 P1 P2 P3
Address/Data
Counter Inputs

8. Pin out of 8052

9. Power on Reset circuit +5V + 10 uF 31 EA/VPP X1 30 pF 19 11.0592 MHz
8.2 K
10 uF +
MHz
EA/VPP X1 X2
RST 31 19 18 9

10. 74LS138 (3-TO-8 DECODER/DEMULTIPLEXER)
The 74LS138 are high-speed CMOS devices and are pin compatible with low power Schottky TTL (LSTTL).
The 74LS138 decoders accept three binary weighted address inputs (A,B and C) and when enabled, provide 8 mutually exclusive active LOW outputs (Y0 to Y7).
This multiple enable function allows easy parallel expansion of the ‘138’ to a 1-of-32 (5 to 32 lines) decoder with just four ‘138’ ICs and one inverter.
The ‘138’ features three enable inputs: two active LOW (G2A and G2B) and one active HIGH (GL). Every output will be HIGH unless G2A and G2B are LOW and GL is HIGH.

11. Features Designed specifically for high speed: Memory decoders
Data transmission systems
74LS138 3-to-8-line decoders incorporates 3 enable inputs to simplify cascading and/or data reception
DM74LS139 contains two fully independent 2-4 line decoder/mulitiplexere lamped for high perform
Typical propagation delay (3 levels of logic)
74LS ns
74LS ns
Typical power dissipation
74LS mW
74LS mW
Connection Diagrams

12. Function Tables

13. Alpha Numeric Display
Alphanumeric displays are designed for numeric indication on instruments, meters, home appliance, communication, computing equipment, and display panels. display available with different character heights

14. Internal structure of a alpha numeric key
Connections of an Alpha Numeric Led display

15. BC557 (PNP TRANSISTOR)
The BC557 transistor is an PNP Epitaxial Silicon Transistor 
The BC557 transistor is a general-purpose transistor in small plastic packages.
It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA PNP general-purpose transistors

16. The arrow in the PNP transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode.

17. Software requirements
Keil an ARM Company makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, integrated environments, evaluation boards, and emulators for ARM7/ARM9/Cortex-M3, XC16x/C16x/ST10, 251, and 8051 MCU families.
Compilers are programs used to convert a High Level Language to object code. Desktop compilers produce an output object code for the underlying microprocessor, but not for other microprocessors.

18. Contd..
i.e., the programs written in one of the HLL like ‘C’ will compile the code to run on the system for a particular processor like x86 (underlying microprocessor in the computer).
For example compilers for Dos platform is different from the Compilers for Unix platform  So if one wants to define a compiler then compiler is a program that translates source code into object code.