DIGITAL STOPWATCH

NIRMAL E|SIJIN UK|VYSHNAV S|VISHNU AR

Submitted to DR.RAJESH K (EEE Department)

COMPONENTS REQUIRED
S.No Items Specifications Quantity
1. IC 7400 1
2. IC CD 4033 2
3. Display 7 Segment 2
4. Resistor 470Ω 2
5. Resistor 10KΩ 2
6. Resistor 1KΩ 1
7. Resistor 10KΩ pot 1
8. Capacitor 100nF 1
9. Slide switch - 1
10. Battery 9V 1
11. Breadboard - 2
12. Voltage regulator U5 7805 1

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CIRCUIT DIAGRAM

2
THEORY
IC CD4033: This is counter and seven segment decoding in one package IC which
is very easy to interface with seven segment displays. This is fully static counter
operational IC and ideal for low power displays. This IC can be used for decade
counting seven segment decimal displays, frequency division seven segment
decimal displays, clocks, watches, timers, counter/display driver for meter
applications.
CLOCK PULSE GENERATION: Using IC 7400 NAND gate generate clock pulse
of frequency 1 Hz .
7-SEGMENT DISPLAY: This is the output display where the numbers will be
shown. It consists of 7 LEDs arranged in a specific pattern to display numbers
from 0 to 9. You can use either a common cathode or common anode display.
A common cathode display connects all cathodes of LEDs together, while a
common anode display connects all anodes together.
RESISTORS: To limit the current flowing through the segments of the 7-
segment display, you’ll need resistors. The value of these resistors depends on
the forward voltage and forward current rating of the LEDs in the display.
SLIDE SWITCH: You’ll need slide switch for controlling the start/stop and
reset functionalities of the stopwatch
U5 7805: voltage regulator is a simple yet effective solution for providing a
stable +5V power supply in electronic circuits. Its ease of use, reliability, and
wide availability make it a popular choice for hobbyists, students, and
professionals alike in a variety of applications. When using the LM7805, it’s
important to consider heat dissipation and ensure adequate cooling, especially
when dealing with high input-output voltage differentials or high load currents.

DESIGN
1.IC 7400 (Clock pulse generator):
R1=1KΩ,R2=10KΩ,C=100uF,
This configuration generates clock pulses with a frequency in the hertz
range, producing a clock cycle of 1 second.

2. CD4033 Decade Counter:

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 • The counter advances on each clock pulse and has outputs from pin
6,7,9,10,11,12,13 of IC CD4033 are connected to F,G,D,A,E,B,C of 7
segment display respectively .
• The carry out (pin5) of first IC is connected to clock (pin 1) of second IC

3. Voltage Regulator:
• Output of voltage regulator (pin 3) is connected to vcc of all ICs and pin 3
of both CD4033 ICs

Operation
The CLK pin of the CD4033 IC receives clock pulses from an external
source, such as a crystal oscillator or a clock signal generator. These clock
pulses are typically generated at a regular interval, such as once per
second, to keep accurate time.The CD4033 IC is a 5-stage Johnson decade
counter, meaning it can count in the sequence 0-12-3-4-5-6-7-8-9-0 and
repeat.Each time a clock pulse is received on the CLK pin, the CD4033
increments its count by one.The CD4033 has 10 output pins labeled QA
to QD, QG, and QE.These output pins represent the binary-coded decimal
(BCD) count. For example, if the count is 3, the pins QA, QB, and QD will
be high (1), and the rest will be low (0).The BCD count from the CD4033
is used to drive the segments of the 7-segment displays. Each digit
(hours, minutes, and seconds) of the clock is displayed on a separate 7-
segment display.The count from the CD4033 is continuously updated and
displayed on the 7-segment displays.For example, if the count represents
the hours, it will cycle from 0 to 9 and then reset to 0, incrementing the
next digit (minutes) accordingly.

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HARDWARE IMPLEMENTATION

RESULTS
Designed and Setup digital stopwatch using IC CD4033

INFERENCE
The operation of a digital clock using the CD4033 IC showcases the integration
of digital counting, display, and timekeeping principles to create a reliable and
user-friendly timekeeping system. With stable clock pulses, accurate time
representation on 7-segment displays, and user-adjustable settings, the clock
serves as both a practical timekeeping tool and an educational platform for
exploring digital electronics concepts.

REFERENCES
https://youtu.be/OkGV0TTTlrc?si=KF1KdTA8QTPt0Zg
https://youtu.be/NZSM5QBPUG4?si=Zx7A4Eg9D4BwXWmhttps://www.cir
cuits-diy.com/how-to-make-digital-stopwatch/
Datasheets of the IC 7400 and CD4033 decade counter.