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Presented byNABANITA CHATTERJEE

Dept. Electrical and Electronics EngineeringNATIONAL INSTITUTE OF SCIENCE AND TECHNOLOGY

BERHAMPUR

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Introduction The aim of the project is to develop a microcontroller

based Air Heater System.

The entire work can be divided into four parts

1. Hardware development

2. Hardware interface with PC3. Parameter Identification

4. Control of process parameter

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Design and Implementation The air is drawn from the atmosphere by a blowing fan.

The air is then heated as it is passed through an electricheater.

The temperature of air should be at a desired level.

The entire setup mainly consists of

1. One heater

2. Three temperature sensors3. Blowing fan

4. PIC microcontroller

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Functional Blocks of the system

An electric heater is placed within a blowing tube

A four pin blowing fan is fitted at that end near the electric heater

Three LM35 temperature sensors are placed at equal distance to sense thetemperature of the air

PCBSensor input

PC

Controller and display unit

fan

Airinflow

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LM35 TEMPERATURE SENSORWhy LM35 ?

Precision integrated circuit temperature sensor

Output voltage is linearly proportional to the celsius temperature

It does not require any external calibration to provide typical accuracies

It is rated to operate over -55 degree C to +150 degree C

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Electric Heater One heater is used for heating the air flowing through the

blowing duct

The supplied power is controlled by a PWM controlarrangement

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4 PIN CPU FAN

The fan is placed at that end of the blowing pipe where the heater is

placed

The fan is required for the cooling purpose

PWM control arrangement is used for the fan speed control

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PIC18F2550 (28 PIN DIP) PIC is referred to as Peripheral Interface Controller

PIC is Harvard Architecture Microcontroller where instructions anddata come from separate sources

USB Features USB V2.0 compliant

On chip USB transceiver with on chip voltage regulator

Support up to 32 endpoints(16 bidirectional)

Wide operating voltage range(2.0 v to 5.5 v)

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COMPLETE CIRCUIT DIAGRAM

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Pictorial View of Real Time System

BLOWING DUCT SYSTEM

Printed Circuit Board

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System Modeling

Q=q + qi

- qo

qt

where

q : rate of heat supplied by the heater

qi : rate at which heat is carried into the volume V

qo : rate at which heat is carried out of the volume V

qt : heat lost from the volume V to the surroundings by radiation andconduction

for heat balance

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Systemparameter Identification

The entire thermal system is approximated as a first order system

The sensors are physically located at certain distance and introduce apure time delay into the system

H(s)=Vo(S)/Vi(S) = (Ke-ds)/(s+1)

Using Visual Basic 6 at the PC end the heater input and the fan speed

can be adjusted manually and so system behaves as an open loopsystem

Process reaction curve method is used to calculate the time constantand the time delay

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Visual Basic 6 Window

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Time Constant Calculation

Temperature profile of sensor

Time constant =260 ms

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Time Delay Calculation (due to sensor 2 )

Time delay =31 ms

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Time Delay Calculation (due to sensor 3 )

Time delay =62ms

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Controller Design

. Proportional controller is designed to control speedof the

fan and the temperatureof the air

One Integral action has been introduced parallel to

proportional controller to improve the performance.

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Proportional (P) ControllerThe controller output at the nth instant is given by

mn = Kpen + bnKp = proportional gain

Bn = fixed biasBlock Diagram of P-Controller

controller o/p mn = Kpen + bn

whereKp = proportional gain

Bn = fixed bias

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P Controller Response

Sensor1 response

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P Controller Response

Sensor2 response

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P Controller Response

Sensor3 response

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PI Controller

m = Kp e(t) + 1/Ti0t e(t).dt + b

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PI Controller Response

Sensor1 response

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PI Controller Response

Sensor2 response

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PI Controller Response

Sensor3 response

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PC End Interfacing

USB 2.0Port is connected to pin 15 and pin 16 of themicrocontroller for interfacing.

The particular PIC microcontroller incorporate fully featured

USB Communication module

So USB compatible data acquisition , monitoring and control is

possible

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Conclusion A microcontroller based air heater system is developed

The temperature of air and speed of the blowing fan can be monitored

and controlled both manually and automatically

The temperature sensors sense the temperature of the air throughoutthe length of the blowing duct and monitoring and control of thecontrol parameters are done at the PC end.

The system designed is simple, easy to operate and can be used as amodel for training and research purpose.

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Application and Future ScopeThe process air heater is used in a number of different types

of industrial plant like food processing industry , chemical

process plants , manufacturing plants etc.

The range of the temperature that is monitored and controlled here

can also be improved

The high level language offers sufficient flexibility for developing

control algorithms using fuzzy logic , neural networks or

genetic algorithms

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THANK YOU