DIGITAL CLOCK




*** Explain the construction, working of Digital clock ?
·           A bridge rectifier is used to convert A.C to D.C
·           7805 IC voltage regulator is used for a constant voltage.
·           A least four 7490 counters, two 7447 binary to 7-segment converters are used for construction.
·           330Ω  resisters 20, some normal LED’s, two common-anode 7-segment LED displays are wanted  to design a Digital Clock.

Construction:-
·           A decade counter  (7490) is used to count from 0 to 9 in a natural mode as a cyclic.
·           We get the 4-bit binary number in QA ,QB,QC and QD  pins as output.
·           Up mode counting process is going on it, after getting the maximum count (number) then returns to zero.
·           We “set it Up” by writing the R01,R02 ,R91 and R92  lines.
·           If both R01  and R02  are connected to 5V or logic1 and either  R91  ,  R92   are connected to ground (logic 0)
·           Then counter will reset. i.e QA ,QB,QC and QD   become zero.
·           If both  R91 and R92  are connected to 5V (logic1), then the count on  QA ,QB,QC and QD goes to 1001.


Working :
To create a divide by 10- counter:
·           First connect pin 5 to  5V and pin-10 to ground.
·           Then connect pin12 to pin-1 & pins 2,3,6,7 are    connected to ground.
·           Then run the input clock signal from the time base or a previous counter on pin 14.
·           The output appears on QA ,QB,QC and QD   .
·            The output of pin11 is connected to the next stage.
To create a divide by 6- counter:
·           First connect pin-5 to 5V and pin-10 to ground.
·            Then connect pin-12 to pin-1 & pin-2 to pin9 & pin-3 to pin-8.
·           Pin- 6 and pin-7 are connected to ground.
·           Run the input clock signal from the time base or a previous counter on pin-14.
·            The output appears on QA ,QB and QC.
·            The output of Pin-8 is connected to next stage.
Creating the second Hand:
·           In this diagram the top two 7490’s divide the 60 Hz signal from the    power supply down by a factor of 60.
·           The 3rd  7490 takes 1 Hz signal as input and divide by 10.
·           Its 4  output’s drive normal LED’s in this diagram.
·           The 4TH  7490 divides the output of the third by 6 and its three outputs drive normal LED’s as well.
Displaying the time as Numerals:
·           To display  the time as numerals we use the 7447 to connect 7490.
·           To power on the 7447 pin-16 is connect to 5V and pin-8 to ground.
·           Connect QA ,QB,QC and QD    from 7490 to pin-7,1,2, &6 of 7447.
·                 Connect 330Ω resistors to pins 13,12,11,10,9,15,14 of the   7447.
·           Connect resistors through a, b, c, d, e, f & g segments to the 7-                   segmentLED.
·            Connect the common anode of the 7-Segment LED to 5V.
To create the minute hand section:
·           We need duplicate “Second hand” portion to create the “Minute hand” section
·           To create the “Hour Hand” portion we want to use an AND gate or inputs of the 7490.
·           After recognizing the binary number 24 ,the hour counter reset to zero.
For a setting mechanism:-
·           For  setting the clock ( digital clock system ) just move the input wires to drive higher- frequency signals into the “minute-hand” section of the clock.
·           In a real clock we use push buttons (or) switches and gates to do the same operation (working).
·           In clocks (or) watches for the alarm & other features we (connected) including low-power chips.
                    The chip is probably embedded directly into the circuit board

Comments

Post a Comment

Popular posts from this blog

UNIT-II MICROCONTROLLER NOTES

Image
Unit: 2 Micro Controller Architecture **Explain the overview of 8051 microcontroller.              The microcontroller is a programmable IC manufactured by VLSI technique and capable of performing arithmetic and logical operations.              The basic functional blocks of a microcontroller are ALU, Flag register, Register array, program counter (PC), Instruction decoding unit, timing and control unit, RAM memory, EPROM/EEPROM memory, parallel I/O port, serial I/O port, programmable timer, ADC and DAC. But all the microcontrollers may not have all the blocks.             In microcontroller ALU performs arithmetic and logical operations. Flag register : The various conditions of the result are stored as status bits in flag register. Register array & Internal   RAM   memory are used as temporary storage device for storing temporary data during execution of a program.              EPROM/EEPROM: The program codes and permanent data are stored in EPROM/EEPROM.   
Read more

UNIT-III Addressing modes & Instruction set

Image
** Explain 8051 instruction set (or) classification of 8051 instruction set (or) types of instructions.             Depending on operation   all instructions are divided in fivel groups: ·          Data Transfer Instructions ·          Arithmetic Instructions ·          Logic Instructions ·          Branch Instructions ·          Bit-oriented Instructions (or) Boolean instructions. Data   Transfer instructions :                      In 8051 microcontroller MOV,MOVC,MOVX,PUSH,POP,XCH and XCHD instructions are used to transfer data between registers and memory locations.           In 8051 microcontroller data transfer operations are : —>     Copy the content of a SFR to internal memory ( or) vice versa —>     Load an immediate operand to SFR/internal memory. —>     Exchange the content of SFR/internal memory with A. —>     Copy the content of program memory to Accumulator. —>      Copy the content of data memory to accumulator
Read more

8051 MC PIN DESCRIPTION

Image
    8051    MICRO CONTROLLER PIN DESCRIPTION The pin diagram of 8051 microcontroller looks as follows − ·          Pins 1 to 8  − These pins are known as Port 1. This port doesn’t serve any other functions. It is internally pulled up, bi-directional I/O port. ·          Pin 9  − It is a RESET pin, which is used to reset the microcontroller to its initial values. ·          Pins 10 to 17  − These pins are known as Port 3. This port serves some functions like interrupts, timer input, control signals, serial communication signals RxD and TxD, etc. ·          Pins 18 & 19  − These pins are used for interfacing an external crystal to get the system clock. ·          Pin 20  − This pin provides the power supply to the circuit. ·          Pins 21 to 28  − These pins are known as Port 2. It serves as I/O port. Higher order address bus signals are also multiplexed using this port. ·          Pin 29  − This is PSEN pin which stands for Program
Read more