MEASUREMENT OF TIME PERIOD OF PENDULUM

Microprocessors Project (EC-316)

Submitted by

Debashree Garbyal (042/EC/15)

Himani Tyagi (070/EC/15)

Teacher Co-ordinator:

Prof. Dhananjay V. Gadre

(Department of Electronics & Communications Engineering)

Netaji Subhas Institute of Technology

University of Delhi

CONTENTS

COMPONENTS USED SYNOPSIS BLOCK DIAGRAM FLOWCHART SCHEMATIC BOARD LAYOUT CODE FLOWCHART BOARD PICTURES GANNT CHART REFRENCES

ACKNOWLEDGEMENT

Firstly we would like to thank Prof. Dhananjay Gadre for his unconditional support and thorough guidance without which this project would not have seen the light of the day. He not only guided us through the project but also played a vital role in helping us relate the theoretical concepts with their practical concepts and instilled in us enthusiasm to LEARN BY DOING.

We would also like to thank our friends and classmates who all worked with us and helped and kept us motivated. Their contribution is truly invaluable.

We would also like to thank all the staff of the Department of Electronics of Netaji Subhas Institute of Technology for providing us with all the requisites for completion of this project.

COMPONENTS USED 8085

8255

16*2 ALPHANUMERIC LCD

555 TIMER (NE555)

ZENER DIODE

DIODE

LDR

3*8 DECODER

LATCH

32K ROM

32K RAM

USB

DC POWER JACK

LED

3MM 5MM

RESISTORS

1K 10K 100K

CAPACITORS

0.1u 10u 4.7u 22p 1u 0.01u

SWITCHES

CONNECTOR

CRYSTAL (4MHz)

PRESET

SYNOPSIS

In this project, an 8085 microprocessor interface is developed to make reliable time period measurements. The time period of each oscillation of a bar pendulum will be measured using this interface. This is done with the help of a laser source and light-dependent resistor (LDR). Initially, the bar pendulum will be oscillated for a particular angle. The arrangement of laser source and LDR will be kept in such a way so that the pendulum’s bob cuts the light’s path during its oscillation. As the bob will cut the path, the light will be momentarily blocked. This will produce a change in current generated in the LDR. This change will then be fed to an Analog to digital convertor so that it can be read by the microprocessor. Thus time period of each oscillation will be recorded. Further, different readings will be taken for different angles.

The motivation behind this project was to achieve the objective of improving the learning process of students at school level. The bar pendulum is a very trivial experiment that physics students do in higher secondary. Yet students sometimes fail to appreciate why ‘the initial angular displacement of the pendulum must be small’. By doing the pendulum experiment with large angle displacements, calculations become complicated; information has to be filtered out regarding the effects of large angle displacement and the damping factor. The damping coefficient is related to the initial displacement itself. This information can only be processed if the time period of each oscillation is measured. Since computers (or microprocessors) can in principle make measurements in microseconds, we were tempted to study the bar pendulum using a microprocessor.

BLOCK DIAGRAM

FLOWCHART

SCHEMATIC DETAILS

To find the time interval of anoscillating pendulum, an arrangement of laser source and light-dependent resistor(LDR) is kept such that the pendulum’s bob cuts the light’s path during its oscillation. As the bob cuts the path, the light is momentarily blocked. This produces a change in current generated in the LDR. For the microprocessor to communicate and understand this change in current, it has to be converted to TTL compatible digital voltage. The conversion and subsequent wave shaping is done using the circuitry shown above.

SCHEMATIC

BOARD LAYOUT

CODE FLOWCHART

BOARD PICTURES

GANTT CHART

REFERENCES

Ramesh Gaonkar, 1993 Microprocessor Architecture, Programming and Applications with 8085/8080A (India: Wiley Eastern Ltd)

http://iopscience.iop.org/ Simple pendulum revisited

Neha Aggarwal, Nitin Verma and P Arun 8255 and 16*2 LCD datasheets.