2. 2
INDEX:
SERIAL
NO.
TITLE PAGE
NO.
1 INTRODUCTION 3
2 BLOCK DAIGRAM 5
3 LIST OF COMPONENTS 6
4 SPECIFICATIONS 7
5 CIRCUIT DISCRIPTION 8
6 'IC' DISCRIPTION 11
7 WORKING 14
8 TROUBLESHOOTING 14
9 RESULT 15
3. 3
INTRODUCTION:
The Tms-8560 is a digital alarm clock each chip includes all the logic
required to bold server types of clocks and timers with a digital display mode.
Hours, minutes, alarm display settings, alarm off setting is done via the standard
set buttons when the chip is in the various display modes.
A digital clock is a type of clock that displays the time digitally, i.e. in
numerals or other symbols, as opposed to an analog clock, where the time is
indicated by the positions of rotating hands. Digital clocks are often associated
with electronic drives, but the "digital" description refers only to the display, not to
the drive mechanism. (Both analog and digital clocks can be driven either
mechanically or electronically, but "clockwork" mechanisms with digital displays
are rare.)
Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a
3.2768 Mega hertz crystal oscillator as in a quartz clock to keep time.
Most digital clocks display the hour of the day in 24 hour format, a more
commonly used hour sequence option is 12 hour format (with some indication of
AM or PM). Emulations of analog-style faces often use an LCD screen, and these
are also sometimes described as "digital".
4. 4
To represent the time, most digital clocks use a seven-segment LED, VFD,
or LCD display for each of four digits. They generally also include other elements
to indicate whether the time is AM or PM, whether or not an alarm is set, and so
on.
Most people find difficulty in setting the time in some designs of digital
clocks in electronic devices where the clock is not a critical function, they may not
be set at all, displaying the default after powered on, 00:00 or 12:00.
Digital clocks that run on mains electricity and have no battery must be reset
every time the power is cut off or if they are moved. Even if power is cut off for a
second, mostclocks will still have to be reset. This is a particular problem
with alarm clocks that have no "battery" backup, because even a very brief power
outage during the night usually results in the clock failing to trigger the alarm in
the morning.
To reduce the problem, many devices designed to operate on household
electricity incorporate a battery backup to maintain the time during power outages
and during times of disconnection from the power supply. More recently, some
devices incorporate a method for automatically setting the time, such as using a
broadcast radio time signal from an atomic clock, getting the time from an
existing satellite television or computer connection, or by being set at the factory
and then maintaining the time from then on with a quartz movement powered by
an internal rechargeable battery.
5. 5
BLOCK DIAGRAMOF DIGITAL ALARM CLOCK:
Because digital clocks can be very small and inexpensive devices that
enhance the popularity of productdesigns, they are often incorporated into all
kinds of devices such as cars, radios, televisions, microwave ovens,
standard ovens, computers and cell phones.
6. 6
LIST OF COMPONENTSUSED IN THIS MODEL:
IC1 – TMS 8560
IC2 – CD4541B
IC BASE- 16 PIN
CRYSTAL – 3.2768MHz
DISPLAY- 7 SEGMENT DISPLAY
R1,R2,R3,R4,R5 – 1KΩ, 1/4Watt per resistor
R6 to R19 - 380Ω
R20 – 1MΩ
C1- 1000µF/25V
C2,C3 – 10Pf
Transistor (Q1,Q2,Q3,Q4)-BC547
Diode (D1,D5,D6,D7)- IN4007
Switch: Push to ON (4 pcs)
9v battery for back-up
Adaptor : i/p = 90-270V with 50-60Hz frequency
o/p = 12V dc with 1A max current
18W= max power dissipation
LED: 3mm (2 pcs)
Buzzer : 1pc
7. 7
SPECIFICATIONS:
1) The chips used in this model of digital alarm clock operate over a wide range
and low stand by operating voltage facilities
2) 7 segment display.
3) Alarm on a 24 hour basis
4) Battery back-up. (in-case of power failure)
5) 50Hz/60Hz is usable as the reference frequency.
6) Single DC power supply
7) AM output
(This is pictorial representation of this model)
10. 10
In the above mentioned circuit a BC547 transistor is a negative-positive-
negative (NPN) transistor that is used for many purposes. Together with other
electronic components, such as resistors, coils, and capacitors, it can be used as the
active component for switches and amplifiers. Like all other NPN transistors, this
type has an emitter terminal, a base or controlterminal, and a collector terminal. In
a typical configuration, the current flowing from the base to the emitter controls
the collector current. A short vertical line, which is the base, can indicate the
transistor schematic for an NPN transistor, and the emitter, which is a diagonal
line connecting to the base, is an arrowhead pointing away from the base.
There are various types of transistors, and the BC547 is a bipolar junction
transistor (BJT). There are also transistors that have one junction, such as the
junction field-effect transistor, or no junctions at all, such as the metal oxide field-
effect transistor (MOSFET). During the design and manufacture of transistors, the
characteristics can be predefined and achieved. The negative (N)-type material
inside an NPN transistor has an excess of electrons, while the positive (P)-type
material has a lack of electrons, both due to a contamination process called doping.
This diode IN-4007 is basically the rectifier diode used for the rectifier
purposes. his is a simple, very common rectifier diode. Often used for reverse
voltage protection, the 1N4007 is a staple for many power, DC to DC step up, and
breadboard projects. 1N4007 is rated for up to 1A/1000V.
11. 11
In the circuit IC-TMS8560 pin diagram:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
10S HR AG & DE
PM & 10S HR B
10S HR C & HR E
HR B & G
HR C & D
HR A & F
10S MIN A & F
10S MIN B & G
10S MIN C & D
10S MIN E & MIN E
MIN B & G
MIN C & D
MIN A & F
COLON OUT
12/24 SELECT
C R INPUT
50/60Hz SELECT
50/60Hz INPUT
SNOOZE INPUT
SLEEP INPUT
HOUR SET
MIN SET
Vss (-)
ALARM DIS
ALARM OFF
SLEEP OUT
ALARM OUT
Vdd (+)
12. 12
How it works?
In this circuits, the heart of the circuits are IC1 (LM8560),
Which has output the 3 way are:
1. The output for drive display Duplex Model numbers (pin 1-14)
2. The output provide alarm signal at pin 16.
3. The output to control electrical appliances with automatic timer.
Two R1, C1 together with was integrating circuit to Provide input to the clock
signal 50 Hz input lock pin (pin 25) of IC1.
Two diode D1, D2 are the switch signal generators to the cathode of display
number for working alternately and relation with the input of IC1. The alarm signal
from pin 16 of IC1, will be entered to the potentiometer P1(Volume), to pin 3 of
IC2 (LM386), that is alarm signal amplifiers to drive the loudspeaker.
The P1 so is fine a alarm sound pressure as you want. And the sleep out signal
from pin 17 that you can continue to use, to control another circuits.
13. 13
IC CD4541 PIN DIAGRAM:
RC TIMER/COUNTER (CD4541):
The RC Timer is used to implement the 5 minute swap of sounds between
buttons. This chip, as set up here, emits a square wave with a 10-minute period.
When the output changes level, the sounds are swapped. The CD4541BC
programmable timer has a 16 stage binary counter, an integrated oscillator that
uses an external capacitor and two resistors. The timer is also programmable by
setting the digital inputs to divide the oscillator frequency by to 2^8, 2^10, 2^13,
2^16. The CD4541BC oscillator frequency can be set by an external RC network
that's by the following formula freq = 1 / (2.3 * Rtc * Ctc) where Rs = ~ 2Rtc and
Rs >= 10,000 ohms
14. 14
WORKING:
First of all connect the circuit as shown above. When the circuit is turned on
the display screen shows 12.00 and then we need to set the time with reference to a
standard clock. The side green LED when ON states AM and vice-versa indicates
PM. In order to set time the switches are provided (hour, minute, alarm switch,
buzzer off switch). And there is port for battery back up also which needs to be is
used only when there is power failure, in this display gets off but the counter in IC
doesn’t stop. And in this case if we had set the alarm it also works.
TROUBLESHOOTING:
In digital alarm clock basically there is no need for calibration, and hence the
chances of manual error doesn’t arise.
Also, we need to keep in mind that all the components connected are of proper
values so the clock works properly.
So the major factors responsible for the malfunctioning of the digital alarm clock
can be:
1. Problem in input suppy.
2. Transformer can be out of order or may be burned out due to high current or
may be the input port may be faulty.
3. Problems with the control buttons as they are mechanical switches, due to
frequent use of switches it may not work.
15. 15
4. Problem with the display screen (shorting of any pins or any kind of damage
to the display IC).
5. If above mentioned all the factors are not responsible for the malfunctioning
of the clock than now we must look out in to the active devices. Firstly we
must checkout the IC’s in the circuit.
6. As there is no particular method to find out the fault in the IC, the only
option is to replace it with another one. We first do this because we don’t
need to deshoulder the IC as a stand is shouldered on the PCB and the IC is
mounted on this stand.
7. The next step is to check out with the buzzer if the problem is only with
sound.
8. If still the problem continues, now we must checkout with the transistors and
the diodes. We can do so by connecting the multimeter between different
terminals and by looking out for the proper voltage drops between the
terminals for proper functioning.
RESULTS:
The time shown by this model is almost accurate with the time
shown by the time shown by the standard clock. the uncertainity of the clock is
almost less then 1% .
