Real Time Clock

REAL TIME CLOCK

The clock described here displays the current time and date and can be build within a small budget  using  AT89C52 microcontroller .it also has a facility to set an alarm and is visable even in the dark.

This construction project will help you understand concepts like real time use of microcontrollers and scanning related to displays .the device is dual powered and switches to battery supply when the mains power is ‘off’.

Circuit description

Fig.1  shows the circuit of the real time clock and fig.3 shows the power supply section .the clock is built around microcontroller AT89C52 (IC1),LTS542 seven segment displays (DIS1 through DIS6),regulator 7805 (IC2) and a few discreate components.

The AT89C52 is a low-power high performance CMOS 8-bit microcontroller .it has 8 kb of flash memory ,256 bytes of RAM ,32 input and output lines ,three 16-bit timers and counters,on chip oscillator ,4 input output port.

 

PART LIST

 SEMICONDUCTORS:

IC1          -AT89C52 microcontroller

IC2          -7805,5V regulator

T1-T2     -BC557 pnp transistor

D1-D4    -1N4007 rectifier diode

DIS1-DIS6-LTS542 common –anode 7 segment display

LED1-LED3-5MM led

RESISTOR:

R1-R5    -10-kilo-ohm

R6-R13  -100-ohm

R14-R21-1 K ohm

R22         - 470 ohm

RNW1   -10 k ohm

CAPACITORS:

C1           -10 micro F

C2,C3     -33Pf

C4           -1000 micro F

C5           -0.1 micro F

MISCELLANEOUS:

X1           -230V AC primary to 12v 500 mA secondary transformer

XTAL      -12MHz crystal oscillator

S1-S5     -Push to on tactile switch

PZ1         -piezobuzzer

 

 

CONSTRUCTIUON  AND  WORKING

An actual-size, single-side  PCB for the real time clock is shown in figure .4 and its component layout in fig.5. assemble the circuit on a PCB to minimise time and assembly errors.carefully assemble the component and double check foe any overlooked error use proper is base for the microcontroller before inserting the ic check all the supply voltages.when power is switched on ,the display should show ’00.00.00’.it will show 01.01.01 when any key is pressed before setting .the table shows the function of switches s1 through s5.to start the date and time setting press s1. the display nwill show ‘set’.now press s2 so that display shows ‘date’.press s3 to get ‘000000’(DDMMYY) on the display .increment the blinking digit number by pressing switch s4 .press s3 to advanced to the next digit .press s3 after setting all the digits of date .the display will show ‘time’.you set time in the same way as date by using switchs s3 and s4 press s3 after setting all the digit of time . now the display will show current time .

                To set the alarm ,press switch s1 twice .the display will show ‘alarm’.press switch s2 once for ‘on’and  then press switch s3. The display will show ‘0000’(HHMM).set the alarm time by using switch s3 and s4 in the same way as when setting the time.the date can be views by pressing any of the keys except s1 and s5.

SOFTWARE

The s/w for the real time clock is written in ‘c’ language and complet using and keil microVISION4 compiler.burn the generated hex code into the microcontroller by using a suitable programmer .all the switches are regularelly scanned .when any switch is pressed ,corresponding action is performed to update the display as per the table.

 

 note:-download the circuit diagram and code and do it .

                                                                                            By:om kumar gaurav