30-04-2012, 12:40 PM
Development and Implementation of Microcontroller-based Digital Clock
[attachment=20942]
Abstract
Electronic clocks have predominately replaced the
mechanical clocks. They are much reliable, accurate, maintenance free
and portable. In general, there are two kinds of electronic clocks. They
are analog clock and digital clock. But digital clocks are more common
and independent of external source. It would be needed the
controlled devices and implementation of software for microcontroller
control system because the hardware devices cannot do any desired
task to execute. In this paper, the microcontroller-based digital clock is
constructed with PIC16F877A and its software program is written
with CCS C program language. Various types of digital clocks and
modules are available in the market nowadays but this clock is
different at least in the accurate time. To be controlling in
microcontroller is only the feature of the clock. The input frequency is
taken from the 50 Hz clock frequency circuit. To show the time,
seven-segment Light Emitting Diodes (LEDs) and four LEDs are used.
Keywords—Actuate Time, CCS C Program Language, Electronic
Clocks, Mechanical Clocks, Microcontroller.
I. INTRODUCTION
IME is such a fundamental concept that it is very difficult to
define. To measure time is needed something that will
repeat itself at regular intervals. The number of intervals
counted gives a quantitative measure of the duration. The
earliest references for the measurement of the time are the moon
and sun. When the sun and the moon were not visible, it was
impossible to know the exact time. So, clocks were developed to
measure out the hours between checks with the sun and the
moon.
The process of measuring time has progressively become
more accurate, and the devices more localized ever since. In our
modern time, the time is predominately measured by
mechanical, and recently by electronic clocks. All clocks
measure time, but different clocks can have status or
importance.
Many centuries have been spent devising method for the
determination and measurement of time. Historically, clocks
and watches of all sorts lie at an important crossroads of science,
technology and society. Changes in timekeeping technology
have influenced the character of scientific
Manuscript received May 31, 2008. This work was supported in part by the
Ministry of Science and Technology, Union of Myanmar.
Pan Thu Tun is with the Mandalay Technological University, Mandalay,
Myanmar. Contact Phone: 095-2-88704(Electronic Engineering Department),
Fax: 095-2-88702( Office,MTU) (e-mail: panthutun[at]gmail.com).
observation, aided the development of other machine
technologies and brought significant revisions in the way
people think about and behave in time.
The first public clock that struck the hours was made and
exerted in Milan in 1335. The oldest servicing clock in England
is that at Salisbury Cathedral, which dates from 1386. About
1500 Peter Henlin, a German locksmith, began to made small
clock driven by a spring.
Fig. 1 Block diagram of the system
The first electronic clock is quartz clock. It is made with a
piece of quartz like liquid crystals which eventually composed
watch displays. Quartz vibrates equally at thousands of times
a second when subjected to an electrical current. Electronic
clock at those vibrations divides then down to minute, second
and fraction of seconds to show time on the dial or display.
Quartz clocks provide more accurate than any mechanical
timekeeper.
In this paper, the more accurate clock using
microcontroller is presented.
II. DESIGN CONSIDERATION FOR SOFTWARE IMPLEMENTATION
In the software implementation process, initialization
processing, LED display processing, time adjustment
processing and time signal processing are considered.
Pan Thu Tun
Development and Implementation of
Microcontroller-based Digital Clock
T
World Academy of Science, Engineering and Technology 42 2008
362
Fig. 2 Flowchart of the initialization processing
First, the required mode is initialized. In this process, RA, RB
and RC ports are defined with the appropriate input or output
mode. The RA port combines analog input and digital input or
output. RA port is used as the digital input or output mode. RB1
port is used for the time signal control and other RBs are used
for the inputs. The RC port is used for the LED control.
Fig. 3 Flowchart of the interrupt
Fig. 4 Flowchart of LED display
In LED display process, one digit is controlled in the one
millisecond interval. LED is turned off first to prevent an
afterimage. The processing of tens of hour is rather
complicated.
In the time adjustment processing, the first fact to notice is
whether or not the selected LED is on. If it is to increase the
time, it will turn the switch clockwise and the switch would be
counter clockwise if it is to decrease.
In the time signal processing which counts up a clock, every
units of hour are renewed if the checking of a time signal is
done.
Fig. 5 Flowchart of time adjustment
III. OPERATION OF THE SYSTEM
Clock input circuit which generates 50 Hz is connected with
the RB0 port of PIC. The RB0 port can make have the function
to do interruption in the change of the input signal. This time, it
detects the rising edge of the input signal and the interruption
occurs. It counts this interruption fifty times and recognizes one
second.
4 MHz resonator is used for the operation clock oscillation by
PIC. The precision of this oscillation frequency doesn't
influence the precision of the clock. The precision of the clock is
decided by the precision of the frequency which is inputted to
RB0. Because it doesn't need the high-speed operation of PIC at
the circuit this time, 4 MHz is used.
In this circuit, the appropriate program and voltages are used
to operate the whole circuit. For digit display, six
seven-segment LEDs to show the hours, minutes and seconds,
two LEDs to separate the minute and hour and another two
LEDs to separate before noon (AM) and after noon (PM) are
used.
World Academy of Science, Engineering and Technology 42 2008
363
The ten seven-segment LEDs are common anode. The
specification of the display position is controlled by the binary
signal which is output from RA0, RA1 and RA2 port of PIC.
This signal is decoded in three-eight decoder (CD4028) and
eight kinds of signals are made. This time, six kinds are used.
Only the transistor which corresponds to the low level decoder
output becomes ON condition. The LED which is connected
with the transistor becomes lighting-up possible condition.
Segments of the lighting-up of each digit are controlled using
seven ports of RC6 from RC0 of PIC. The output of these ports
is common to all the LEDs. The LED lights up when the RC port
is low level. The brightness of the LED depends on the kind of
the LED. When the brightness is different extremely, the
resistors which are connected with the RC ports should be
separated.
Fig. 6 Circuit diagram for digital clock
IV. CONCLUSION AND FURTHER EXTENSIONS
In this paper, the microcontroller-based digital clock is
mainly controlled by the clock pulse frequency. The clock pulse
frequency can be generated by using the IC1 555. The clock
pulse frequency can be obtained from other methods such as the
power line frequency and the internal oscillator IC with RC
circuit and so on. The power line frequency will not get more
accuracy than the quartz crystal. The 555-timer astable mode
can be used for this purpose.
In the display, there are needed to give the outputs of seconds,
minutes and hours and AM/PM. In this display system, the
output of PIC is connected with the input of decoder (CD4028)
to drive the seven-segment LEDs. The decoder (CD4028) has
four inputs and ten outputs. But, in this circuit three inputs and
six outputs are used. So, one input pin is grounded and four
outputs pins are not used.
In the music section which generates the time, the output
frequency is nearly 600 Hz. In the electronic circuits, the audio
range is between 20 Hz and 20 kHz. So, 600 Hz is the suitable
output frequency.
This paper can be extended to cover electronic fields and
would like to be a little support for other researchers in the field
of electronics. Some further extensions performances which can
also be carried out are described as follows.
The microcontroller-based digital clock can be provided with
the date, month and year circuits. The output of day indicator
can be shown by connecting with the output pins of CD4028,
pin seven and eight. But the required instructions are added to
the existing program. If the month indicator is wanted to show,
the remaining input pin, pin D is connected with the output pin
of PIC, RA3 and then to drive the seven-segment LEDs output
pins of CD4028, pin zero and nine are used.
Furthermore, the year indicator is wanted to add, the decoder
must be changed. Because CD4028 has only ten outputs, it is not
sufficient to show the year indicator. So four-sixteen decoder
(74HC154) should be used instead of CD4028.
World Academy of Science, Engineering and Technology 42 2008
364
The circuit can provide with another alarm circuit. The
existing alarm circuit is simple 555-timer circuit and it will ring
the alarm at every hour. If the alarm is wanted to ring at the
specified time, the program is rewritten. Moreover, the pleasant
song can be heard by using the melody ICs.
V. EXPERIMENTAL RESULTS
The experimental results of this system are shown in Fig. 7
and Fig. 8.
Fig. 7 Top view photograph of digital clock
Fig. 8 Front view photograph of digital clock
ACKNOWLEDGMENT
Firstly the author would like to thank his parents: U Kyaw
Yin and Daw Mya Sein for their best wishes to join the PhD
research. Special thanks are due to his Supervisor/ Head of
Electronic Engineering Department, MTU, Myanmar: Dr. Yin
Mon Myint. The author would like to express his thank to his
friends. The author greatly expresses his thanks to all persons
whom will concern to support in preparing this paper.
REFERENCES
[1] Predko, M. 2001. Programming and Customizing PIC Microcontrollers,
2nd ed. Printed by Prentice-Hall, Inc.
[2] Penfold, R. A. 1997. An Introduction to PIC Microcontrollers. 1st ed.
Printed by BERNARD BABANI (publishing) LDT.
[3] Microchip. 2001. PIC16F873 Data Sheet. Printed by Microchip
Technology, Inc in the United States of America.
[4] Bolyestand, R. Electronic Devices and Circuit Theory. 5th ed. Printed by
Prentice-Hall, Inc.
[5] Iovine, J. 2002. PIC Microcontroller Project Book. Printed by Mc
Graw-Hill.
[6] U Maung Maung Myat. 2001. Electronic Professionals, Volume 2.
[7] Tyyer, S. B. 1995. “Programmable Digital Clock”, Electronic Project
Volume 16.
[8] Microchip. No Date. Data Sheet of PIC16F873 28/40-Pin 8-bit CMOS
FLASH microcontroller. <http://www.microchip.com>.
[9] Inoue, S. “Digital Clock”, PIC Circuit Gallery. October 2005.
<http://www.hobby.com>.
[10] Nigel Gardner. An Introduction to Programming the microchip PIC in
CCS.
Pan Thu Tun was born in 1982, April 1. Graduated in August, 2004 with B.E
(Electronic) and finished Master degree on March, 2006 with M.E (Electronic).
Now, he is a PhD Candidate of Electronic Engineering Department, MTU,
Myanmar.
He served as a Demonstrator at Mandalay GTC from January, 2001 to
January, 2004 when he was attending the Special Engineering Course in MTU.
From 4, Novenber, 2004 to 31, March, 2008, he promoted as an Assistant
Lecturer of Mandalay Technological University and from 1, April, 2008 to
now, he promoted as a lecturer, Department of Technical and Vocational
Education, Myanmar. For his Master Thesis, he wrote the results of his research
“Design and Construction of microcontroller-based Digital Clock”. Now, he is
making his PhD research at Mandalay Technological University (MTU),
Myanmar with the title of “Development of Wireless Remote Control for
Take-off and Landing System in UAV’.
Mr. Pan Thu Tun made his first publication of International Paper at this
paper “Development and Implementation of Microcontroller based Digital
Clock’.
[attachment=20942]
Abstract
Electronic clocks have predominately replaced the
mechanical clocks. They are much reliable, accurate, maintenance free
and portable. In general, there are two kinds of electronic clocks. They
are analog clock and digital clock. But digital clocks are more common
and independent of external source. It would be needed the
controlled devices and implementation of software for microcontroller
control system because the hardware devices cannot do any desired
task to execute. In this paper, the microcontroller-based digital clock is
constructed with PIC16F877A and its software program is written
with CCS C program language. Various types of digital clocks and
modules are available in the market nowadays but this clock is
different at least in the accurate time. To be controlling in
microcontroller is only the feature of the clock. The input frequency is
taken from the 50 Hz clock frequency circuit. To show the time,
seven-segment Light Emitting Diodes (LEDs) and four LEDs are used.
Keywords—Actuate Time, CCS C Program Language, Electronic
Clocks, Mechanical Clocks, Microcontroller.
I. INTRODUCTION
IME is such a fundamental concept that it is very difficult to
define. To measure time is needed something that will
repeat itself at regular intervals. The number of intervals
counted gives a quantitative measure of the duration. The
earliest references for the measurement of the time are the moon
and sun. When the sun and the moon were not visible, it was
impossible to know the exact time. So, clocks were developed to
measure out the hours between checks with the sun and the
moon.
The process of measuring time has progressively become
more accurate, and the devices more localized ever since. In our
modern time, the time is predominately measured by
mechanical, and recently by electronic clocks. All clocks
measure time, but different clocks can have status or
importance.
Many centuries have been spent devising method for the
determination and measurement of time. Historically, clocks
and watches of all sorts lie at an important crossroads of science,
technology and society. Changes in timekeeping technology
have influenced the character of scientific
Manuscript received May 31, 2008. This work was supported in part by the
Ministry of Science and Technology, Union of Myanmar.
Pan Thu Tun is with the Mandalay Technological University, Mandalay,
Myanmar. Contact Phone: 095-2-88704(Electronic Engineering Department),
Fax: 095-2-88702( Office,MTU) (e-mail: panthutun[at]gmail.com).
observation, aided the development of other machine
technologies and brought significant revisions in the way
people think about and behave in time.
The first public clock that struck the hours was made and
exerted in Milan in 1335. The oldest servicing clock in England
is that at Salisbury Cathedral, which dates from 1386. About
1500 Peter Henlin, a German locksmith, began to made small
clock driven by a spring.
Fig. 1 Block diagram of the system
The first electronic clock is quartz clock. It is made with a
piece of quartz like liquid crystals which eventually composed
watch displays. Quartz vibrates equally at thousands of times
a second when subjected to an electrical current. Electronic
clock at those vibrations divides then down to minute, second
and fraction of seconds to show time on the dial or display.
Quartz clocks provide more accurate than any mechanical
timekeeper.
In this paper, the more accurate clock using
microcontroller is presented.
II. DESIGN CONSIDERATION FOR SOFTWARE IMPLEMENTATION
In the software implementation process, initialization
processing, LED display processing, time adjustment
processing and time signal processing are considered.
Pan Thu Tun
Development and Implementation of
Microcontroller-based Digital Clock
T
World Academy of Science, Engineering and Technology 42 2008
362
Fig. 2 Flowchart of the initialization processing
First, the required mode is initialized. In this process, RA, RB
and RC ports are defined with the appropriate input or output
mode. The RA port combines analog input and digital input or
output. RA port is used as the digital input or output mode. RB1
port is used for the time signal control and other RBs are used
for the inputs. The RC port is used for the LED control.
Fig. 3 Flowchart of the interrupt
Fig. 4 Flowchart of LED display
In LED display process, one digit is controlled in the one
millisecond interval. LED is turned off first to prevent an
afterimage. The processing of tens of hour is rather
complicated.
In the time adjustment processing, the first fact to notice is
whether or not the selected LED is on. If it is to increase the
time, it will turn the switch clockwise and the switch would be
counter clockwise if it is to decrease.
In the time signal processing which counts up a clock, every
units of hour are renewed if the checking of a time signal is
done.
Fig. 5 Flowchart of time adjustment
III. OPERATION OF THE SYSTEM
Clock input circuit which generates 50 Hz is connected with
the RB0 port of PIC. The RB0 port can make have the function
to do interruption in the change of the input signal. This time, it
detects the rising edge of the input signal and the interruption
occurs. It counts this interruption fifty times and recognizes one
second.
4 MHz resonator is used for the operation clock oscillation by
PIC. The precision of this oscillation frequency doesn't
influence the precision of the clock. The precision of the clock is
decided by the precision of the frequency which is inputted to
RB0. Because it doesn't need the high-speed operation of PIC at
the circuit this time, 4 MHz is used.
In this circuit, the appropriate program and voltages are used
to operate the whole circuit. For digit display, six
seven-segment LEDs to show the hours, minutes and seconds,
two LEDs to separate the minute and hour and another two
LEDs to separate before noon (AM) and after noon (PM) are
used.
World Academy of Science, Engineering and Technology 42 2008
363
The ten seven-segment LEDs are common anode. The
specification of the display position is controlled by the binary
signal which is output from RA0, RA1 and RA2 port of PIC.
This signal is decoded in three-eight decoder (CD4028) and
eight kinds of signals are made. This time, six kinds are used.
Only the transistor which corresponds to the low level decoder
output becomes ON condition. The LED which is connected
with the transistor becomes lighting-up possible condition.
Segments of the lighting-up of each digit are controlled using
seven ports of RC6 from RC0 of PIC. The output of these ports
is common to all the LEDs. The LED lights up when the RC port
is low level. The brightness of the LED depends on the kind of
the LED. When the brightness is different extremely, the
resistors which are connected with the RC ports should be
separated.
Fig. 6 Circuit diagram for digital clock
IV. CONCLUSION AND FURTHER EXTENSIONS
In this paper, the microcontroller-based digital clock is
mainly controlled by the clock pulse frequency. The clock pulse
frequency can be generated by using the IC1 555. The clock
pulse frequency can be obtained from other methods such as the
power line frequency and the internal oscillator IC with RC
circuit and so on. The power line frequency will not get more
accuracy than the quartz crystal. The 555-timer astable mode
can be used for this purpose.
In the display, there are needed to give the outputs of seconds,
minutes and hours and AM/PM. In this display system, the
output of PIC is connected with the input of decoder (CD4028)
to drive the seven-segment LEDs. The decoder (CD4028) has
four inputs and ten outputs. But, in this circuit three inputs and
six outputs are used. So, one input pin is grounded and four
outputs pins are not used.
In the music section which generates the time, the output
frequency is nearly 600 Hz. In the electronic circuits, the audio
range is between 20 Hz and 20 kHz. So, 600 Hz is the suitable
output frequency.
This paper can be extended to cover electronic fields and
would like to be a little support for other researchers in the field
of electronics. Some further extensions performances which can
also be carried out are described as follows.
The microcontroller-based digital clock can be provided with
the date, month and year circuits. The output of day indicator
can be shown by connecting with the output pins of CD4028,
pin seven and eight. But the required instructions are added to
the existing program. If the month indicator is wanted to show,
the remaining input pin, pin D is connected with the output pin
of PIC, RA3 and then to drive the seven-segment LEDs output
pins of CD4028, pin zero and nine are used.
Furthermore, the year indicator is wanted to add, the decoder
must be changed. Because CD4028 has only ten outputs, it is not
sufficient to show the year indicator. So four-sixteen decoder
(74HC154) should be used instead of CD4028.
World Academy of Science, Engineering and Technology 42 2008
364
The circuit can provide with another alarm circuit. The
existing alarm circuit is simple 555-timer circuit and it will ring
the alarm at every hour. If the alarm is wanted to ring at the
specified time, the program is rewritten. Moreover, the pleasant
song can be heard by using the melody ICs.
V. EXPERIMENTAL RESULTS
The experimental results of this system are shown in Fig. 7
and Fig. 8.
Fig. 7 Top view photograph of digital clock
Fig. 8 Front view photograph of digital clock
ACKNOWLEDGMENT
Firstly the author would like to thank his parents: U Kyaw
Yin and Daw Mya Sein for their best wishes to join the PhD
research. Special thanks are due to his Supervisor/ Head of
Electronic Engineering Department, MTU, Myanmar: Dr. Yin
Mon Myint. The author would like to express his thank to his
friends. The author greatly expresses his thanks to all persons
whom will concern to support in preparing this paper.
REFERENCES
[1] Predko, M. 2001. Programming and Customizing PIC Microcontrollers,
2nd ed. Printed by Prentice-Hall, Inc.
[2] Penfold, R. A. 1997. An Introduction to PIC Microcontrollers. 1st ed.
Printed by BERNARD BABANI (publishing) LDT.
[3] Microchip. 2001. PIC16F873 Data Sheet. Printed by Microchip
Technology, Inc in the United States of America.
[4] Bolyestand, R. Electronic Devices and Circuit Theory. 5th ed. Printed by
Prentice-Hall, Inc.
[5] Iovine, J. 2002. PIC Microcontroller Project Book. Printed by Mc
Graw-Hill.
[6] U Maung Maung Myat. 2001. Electronic Professionals, Volume 2.
[7] Tyyer, S. B. 1995. “Programmable Digital Clock”, Electronic Project
Volume 16.
[8] Microchip. No Date. Data Sheet of PIC16F873 28/40-Pin 8-bit CMOS
FLASH microcontroller. <http://www.microchip.com>.
[9] Inoue, S. “Digital Clock”, PIC Circuit Gallery. October 2005.
<http://www.hobby.com>.
[10] Nigel Gardner. An Introduction to Programming the microchip PIC in
CCS.
Pan Thu Tun was born in 1982, April 1. Graduated in August, 2004 with B.E
(Electronic) and finished Master degree on March, 2006 with M.E (Electronic).
Now, he is a PhD Candidate of Electronic Engineering Department, MTU,
Myanmar.
He served as a Demonstrator at Mandalay GTC from January, 2001 to
January, 2004 when he was attending the Special Engineering Course in MTU.
From 4, Novenber, 2004 to 31, March, 2008, he promoted as an Assistant
Lecturer of Mandalay Technological University and from 1, April, 2008 to
now, he promoted as a lecturer, Department of Technical and Vocational
Education, Myanmar. For his Master Thesis, he wrote the results of his research
“Design and Construction of microcontroller-based Digital Clock”. Now, he is
making his PhD research at Mandalay Technological University (MTU),
Myanmar with the title of “Development of Wireless Remote Control for
Take-off and Landing System in UAV’.
Mr. Pan Thu Tun made his first publication of International Paper at this
paper “Development and Implementation of Microcontroller based Digital
Clock’.