This document describes an automatic temperature control system using an 8085 microprocessor. The system uses an AD590 temperature sensor, differential amplifier, ADC0808 converter, and 8085 microprocessor to monitor and control the temperature. It aims to minimize manual intervention and control temperature in industrial plants. The system works by comparing the measured temperature to upper and lower setpoints and turning the heater or cooler on/off accordingly to maintain the temperature within the limits.

1. AUTOMATIC TEMPERATURE CONTROL
USING 8085 MICROPROCESSOR
MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY
BHOPAL (M. P.), INDIA– 462003
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Presented By:RANJAN KUMAR
M.Tech (electrical drives)
Scholar no.: 182113211
TEACHER: Dr. MEENA AGARWAL

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Definition of TemperatureControl
Temperature control is a process in which change of temperature
of a space (and objects collectively there within) is measured or
otherwise detected, and the passage of heat energy into or out of the
space is adjusted to achieve a desired average temperature.
Aim of the Project
➢To control temperature
➢To minimize manual intervention using an intelligent processor
(such as 8085 microprocessor)
➢It controls the temperature of any industrial plant.

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ATC using 8085 Microprocessor
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An Automatic Temperature Control Unit mainly divided into three
parts:-
❖Temperature input
❖unit Processing unit
❖Control output unit
Overview of ATC unit
➢ The 8085 based trainer kit forms the basic processing unit.
➢ The Analog-to-Digital converter unit and temperature sensor forms the
temperature input unit.
➢ The switching ON/OFF of the heater / cooler controls the heat supplied to
the plant

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Basic operationof the temperature control unit
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➢ Operationally, the system requires two set points
➢ Upper set point
➢ Lower set point
➢ Whenever the temperature of the plant exceeds the upper limit or
recede the lower limit heater/cooler is turned-off, so that a
temperature is maintained within limits.
The main hardware consists of automatic temperature control
system
1) 8085 Microprcessr unit
2) ADC interface board
3) AD 590 temperature sensor
4) Amplifier (741 op-Amp)

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The 8085 trainer kit consistsof
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8085 MPU IC
8KB EPROM
8KB RAM
Keyboard and display controller 8279
Programmable Peripheral interface 8255(PPI)
21 key hex-keypad
Six numbers of seven segment LED’s

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The ADC interface board consists of
◼ ADC 0808, which is an 8-bit converter with eight
channels of input.
◼ Interfaced with the 8085 through 50-pin bus expansion
connector.

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Basic block diagram Architecture of ATC system
Sensor Amplifier
Micro-
processor unit
ADC
converter
Analog Signal Amplified Analog Signal Converted DigitalSignal
Different types of temperature sensors
◼ Thermistor
◼ Thermocouples
◼ Solid state temperature sensor
◼ I.C. Temperature sensor(LM134-3)

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Entire Circuit Diagram of control unit
Heater
Sensor(AD590)
Differential Amplifier
Using (Op-amp)
ADC Converter
(0808 IC)
8085
Microprocessor
unit
Water

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Some Thermistor and its circuit diagram
Rod Thermistor FIG.-Circuit diagram of
Thermistor
Bead Thermistor
Disc
Thermistor

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Thermocouples
FIG.- K type Thermocouple
Fig.- A Typical
Thermocouple Circuit

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Solid State Temperature Sensor
TEMPERATURE SENSOR
Fig.-AD 590 IC
Fig:-Calibration accuracy Vs.
Temperature Curve of AD 590

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The sensor which We choose for this project
Features of AD590
Sensitivity
Better than LM135
Great calibration accuracy
Fast temperature measurement
FIG:-AD590

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Differential Amplifier usingop-amp
FIG:-Implementation of the
circuit on Bread-Board
FIG:-circuit diagram of
Differential Amplifier

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Interfacing the 0808 with the 8085 trainerkit
D7 D6 D5 D4 D3 D2 D1 D0
Port A EOC
Port B 2-1
2-2 2-3 2-4 2-5
2-6 2-7 2-8
Port C ALE START COOLER HEATER

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ADC interfacing with the microprocessor
A
D
C
0
8
0
8

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START
CALL SUBROUTINE ADC : SET
(C7), SET START (C6)
READ EOC (A7)
IS DATA
<
19H (.5V)?
,
33H(IV)?
IS EOC- -=0
N
RESET ALE(C7) READ PORT B
N
CALL SUBROUTINE
HEATER
Y
ALE
Y
FOR DATA
IS DATA
>
98H (3V)?
Y
CALL SUBROUTINE
COOLER
FIG:-DESIGN STEPS WITH THE HELP OF FLOWCHART

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If we choose any other component other than microprocessor :
Magnitude Comparator
FIG:-Block diagram of IC 7485

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Application of Automatic Temperature control System
In Chemical Industry

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Nature Science

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IN DAILY LIFE
FIG:-MICRO-OVENFIG:-ROOM TEMPERATURE
CONTROLLER

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Advantage of ATCsystem
ATC system using 8085 is very simple
circuit.
As 8085 microprocessor Memory used
as stack memory( when needed), we the
programmer can store already all
possible combination of data
corresponding to the temperature in the
memory stack.
It has minimum circuitry.

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Limitation of the ATC System
The system is temperature bounded.
We just conceptually say that huge no. of
peripheral devices must be connected through
the two port, but at the time of
implementation of the project we are not able
to connect all possible devices with the
microprocessor port.
The sensibility of the system is 0.20C,so any
change in temperature less than that can’t be
recognized by the system.

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Future scope of the project
This is a very basic automation system of
temperature control.
Few changes may be needed in the control
circuit for controlling the system with the help of
Microcontroller.
It should also be able to control various
temperature.
If we use microcontroller rather than
microprocessor the cost will be minimum.
We can also use relay to control the heater and
cooler subroutine automatically.

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References
➢ Microprocessor Architecture, Programming and applications with 8085- By R.S.
Gaonkar, Fifth Edition (Penram international publishing).
➢ Microprocessor and digital systems-Douglas V.Hall, (McGraw Hill Book co.)
➢ Introduction to microprocessor- A.P.Mathur, (Tata McGraw Hill)
➢ MME 85S manual
➢ IC DATA handbook
➢ National semiconductors Datasheets
➢ http://www.wisc-online.com/objects/ViewObject.aspx?ID=DIG3403
➢ http://www.scribd.com/doc/4616314/8085-Microprocessor
➢ http://www.electronic-circuits- diagrams.com/computersimages/computersckt2.shtml
➢ http://www.analog.com/en/AD590/productsearch.html
➢ http://www.national.com/analog
➢ http://www.omega.com/prodinfo/thermistor.html
➢ http://en.wikipedia.org/wiki/Operational_amplifier_applications

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RANJAN SINGH
MANIT BHOPAL
THANK
YOU