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CONTACTLESS
TACHOMETER
Jasmeet Singh 67/EC/13
Jatin Singh - 69/EC/13
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Contents
S. NO. TOPIC PAGE NO.
1. Acknowledgement 3
2. Abstract 3
3. Components Used 4
4. Schematic Details 5
5. Block Diagram 7
6. Schematic(s) 8
7. Board Layout 10
10. Code 11
11. Conclusion 13
12. Bibliography
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Acknowledgement
This is to acknowledge the invaluable contributions made by Prof.
Dhananjay Gadre for helping us at each stage of the project.
Furthermore we thank you for providing the necessary components and
access necessary to the facilities which enabled us to work comfortably
on our project.
We would also like to express our gratitude to the members of the
Microprocessors lab for their patience.
Abstract
The main aim of the project is to develop a contactless tachometer using
8085 Microprocessor.
The project has a LCD which displays the speed of the motor in rpm.
The blade of the motor is detected using phototransistor. The output of
comparator is fed at RST7.5 and the 555 timer generates a 1.1 second
pulse which is fed at RST6.5. Thus using 8085 microprocessor we can
calculate the number of pulses of RST 7.5 when RST 6.5 is high which
gives us the speed in revolutions per second.
The number of pulses are observed and after some calculations the
speed(in rpm) is displayed on the LCD.
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Components Used
Component Name Quantity Model No.
8085 Microprocessor 1 8085AHC
NAND Gate IC 1 74HC00N
RAM 32K 1 62256
EEPROM 32K 1 28C256
Latches 1 74HCT573N
Decoder 1 74HCT138N
8255 1 82C55AC
555 timer 1 10k
Comparator 1 LM311
Crystal 4MHz 1
Resistors - 1k,10k,2.2k,3.3k,100k
Capacitors - 0.1uF, 22uF, 10uF,100uf
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Schematic Details
8085 Microprocessor
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Data Bus Latch
8085 has a multiplexed data bus which must be de-multiplexed so that
general purpose memory devices can be used. The lower order data bus
is de-multiplexed using the ALE signal and the latch 74HCT573N.As
ALE goes low, the address on the bus AD7-AD0 is latched and the 8
output lines of the latch serve as lower order address lines. The address
on the latch remains the same until the next ALE signal.
Memory
32K of EEPROM is used. The memory addresses are from the range
0000H to 7FFFH. 32K of RAM is used. The memory addresses range is
from 8000H to FFFFH.
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Block Diagram
LCD
8255 8085
Micro
Processor
RAM
ROM
Motor
Phototransistor
Comparator
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Schematic(s)
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Board Layout
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Code
.ORG 0000H
LXI SP,0FFFFH ; initialize stack pointer
JMP start
.org 02000h
.DB 057h,065h,06Ch,063h,06Fh,06Dh,065h,020h ;Welcome to
.DB 074h,06fh,054h,061h,063h,068h,06Fh,06Dh ;Tachometer
.DB 065h,074h,065h,072h,020h
.ORG 0034H
JMP six_serv
.ORG 003CH
JMP seven_serv
six_serv: RIM ;service routine for rst6.5
ANI 40H ;check if rst7.5 is present
JNZ increment
JMP main ;if rst7.5 is not present JMP to main
increment: INR E ;increment register E for every rst7.5
RET
seven_serv: CALL six_serv ;service routine for rst7.5
JMP main
hex_to_bcd: MOV A,E
MOV B,E
ANI 0FH
MOV C,A
MOV A,B
ANI F0H
ADD C
show_speed: MOV E,A ;E now holds speed in bcd
MVI A,98H
OUT 03H
mvi a,038h ;lcd initialzation command
out 01h
call cmd
mvi a,00fh
out 01h
call cmd
mvi a,006h
out 01h
call cmd
mvi a,001h
out 01h
call cmd
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mvi a,093h ;set location in lcd
out 01h
call cmd
lxi d,02000h
mvi b,00Ah
wel: ldax d
out 01h
call data
inx d
dcr b
jnz wel
mvi a,d0h
out 01h
call cmd
mvi b,011h
cmd: push psw
push d
mvi a,02h
out 03h
mvi a,00h
out 03h
mvi d,0ffh
data: push psw
mvi a,03h
out 02h
mvi a,01h
out 02h
pop psw
ret
start: MVI E,00H
main: EI
no_intr: DI ;if no interrupt is present it means first cycle is completed now disable the interrupt
CALL hex_to_bcd ;convert speed from hex to bcd
CALL show_speed ;show the speed on lcd
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Conclusion Overall working experience on this project was a great. This practical project not only strengthened our concepts but also showed us how to apply theoretical knowledge to build something useful. It made us aware of the advances that the electronics industry has made. It also helped us understand the integration of hardware and software.
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BIBLIOGRAPHY
Ramesh Gaonkar, Microprocessor Architecture, Programming and Applications with the 8085, Sixth edition.
http://www.alldatasheet.com/
http://www.circuitstoday.com/digital-tachometer-using-8051