IRF - report

8/14/2019 IRF - report

1/66

INFRA RED HEATING FOR FURNACE USING

SOLID STATE RELAY

A PROJECT REPORT

Submitted by

R. BHASKAR (Reg No. 31704114008)

MIDHUN BABU (Reg No. 31704114027)

in partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING

IN

MECHANICAL ENGINEERING

St. JOSEPHS COLLEGE OF ENGINEERING

ANNA UNIVERSITY: CHENNAI 600025

APRIL 2008


2/66

BONAFIDE CERTIFICATE

Certified that this project report INFRA RED HEATING FOR

FURNACE USING SOLID STATE RELAY is the bonafide work of

MIDHUN BABU (31704114027) and BHASKAR.R (31704114008) ,

who carried out the project work under my supervision.

SIGNATURE SIGNATURE

Dr.S.JOSE Mr.ARUN VASANTHA

GEETHAN

HEAD OF THE DEPARTMENT SUPERVISOR

Department of Mechanical Engineering LECTURER

Department of MechanicalEngineering

St. Josephs College of Engineering St. Josephs College of

Engineering

Jeppiaar Nagar Jeppiaar Nagar

Old Mahabalipuram road Old Mahabalipuram road

Chennai 600 119 Chennai 600 119


3/66

ACKNOWLEDGEMENT

We are personally indebted to so many people that a complete

acknowledgement would be encyclopedic.

Our sincere thanks and profound sense of gratitude goes to our respected

chairman Thiru.Jeppiaar M.A., B.L., for all his efforts and administration

in educating us in his premiere institution. I take this opportunity to thank

our Director, Dr. Babu Manoharan M.A., M.B.A., Phd., for his kind co-

operation in helping us complete this project.

We would like to express our gratitude to our principal Prof. Jolly

Abraham M.E., M.I.E., and the head of the department Dr.S.Jose M.E.,

Phd., for their guidance and for their advice all through our tenure.

We convey our sincere thanks to our internal guide Mr. K. Arun Vasantha

Geethan for his valuable suggestions throughout the project duration

We sincerely thankMr. Senthil Kumar for his valuable suggestions and

expert guidance in completing this project.


4/66

ABSTRACT

The objective of this project is to use infra red heating technique for

paint baking purposes. We have fabricated a furnace which makes use of

Infra Red lamp for heating component which is to be baked. The main

advantage of this technique is that, Infra Red lamp consumes less power and

less time for heating the component.

The temperature to which the component is to be heated is controlled

using a solid state relay which is much better than the conventional relay and

has a lot of advantages. We have manufactured a prototype of a furnace with

which we heat a component and control the temperature using electronic

control circuit which in turn makes use of a embedded control circuit

We use a k- type thermocouple for sensing the temperature in the

furnace. Temperature acquired from the thermocouple is indicated on the

LCD screen. The Embedded control circuit will also compare the

temperature acquired with the set temperature and control action, if any, will

be done by the solid-state relay that avoids instantaneous heating.


5/66

CHAPTER 1

INTRODUCTION


6/66

INTRODUCTION

Paint drying furnaces have been widely adopted by industry to make

their product have an attractive appearance and have a longer life by

applying the paint on the surface of the product. In the manufacture of some

automotive parts such as radiators and condensers, painting of the part is

required for both appearance and corrosion-resistance reasons. These

industrial components which are painted using spray painting or other

methods have to be heated to be dried.

The method of heating can also be used to heat a part or component

prior to its painting process. This has been utilized in the powder painting

technology in which dry powder paint is deposited on a preheated part such

that the heat energy will help to melt and flow the dry powder paint in

forming a paint film.

CONVENTIONAL METHODS

There are a few methods of paint drying. For simple applications paint

drying can be done just by placing the product in the open and exposed to

the sun. There are some conventional methods for paint drying. Some

commonly used methods are:


7/66

1. AIR STREAM DRIERS

2. BELT DRIERS

3. DRYING OVENS

AIR STREAM DRIERS

This is a simple method of paint drying. It uses stream of hot air to

heat the product and dry the paint. Dry air is heated to high pressures using

heating coils or other sources and regulated using fans and nozzles. The hot

air s directed towards the product to be dried on specific painted portions if

necessary. Instead of hot dry air steam can also be used for certain

applications. Such processes consume a lot of energy and high temperatures

can not be attained. Thus this is suitable only for certain applications

BELT DRIERS

This type of drier has a higher temperature range. It consists of a

housing with built-in conveyer belts for the product running over heating

plates. Automatic belt control ensures precision belt operation. The

temperature to which the product is subjected during the drying process has

a significant effect on the achievable product quality. The belts run over a

number of heating zones and over a cooling zone at the end. Each zone can

be controlled separately, allowing the temperature of the heating surfaces to

be adapted to the specific requirements of the product.


8/66

The entire belt drying system is controlled by a stored program control

(SPC) and operated over a control panel or PC.

A length of 300-400 feet of drying oven is frequently required tosufficiently dry such parts. Lengthy drying ovens are undesirable because

they not only occupy extensive floor space area in a manufacturing plant, but

also consume enormous amount of energy and require substantial manpower

for maintenance. The excessive amount of time necessary to travel through

the lengthy drying ovens is also a problem for achieving plant efficiency.

DRYING OVENS

This is the most commonly used method for high temperature

applications. This is mostly done using conventional furnaces or ovens

which use heating coils or burning to attain heating. This baking method

uses Hot Air Ovens provided with Nichrome heaters in coil form. Smallovens can be operated on 220v, single phase, AC supply. However large

ovens, used in production processes are rated from 3 kW to 100 kW or even

more. These furnaces will require 440v, three phases, AC supply.

In such furnaces and ovens the heating is not uniformly distributed.

Small fans are used to regulate uniform heating which slows down the

process and also reduces the electrical efficiency.


9/66

PROJECT OBJECTIVES

Our project is designed to achieve the following objectives:

1. INCREASED HEATING EFFICIENCY

2. LESS COMPLEXITY WITH EASY INTERFACE

3. SOLID STATE CLOSED LOOP CONTROL

4. INTERNATIONAL COMPATABILITY

5. OPEN THERMOCOUPLE PROTECTION

6. DIRECT DIGITAL DISPLAY

INFRA RED HEATING

In our project we intend using Infra Red Heating. Heating process is

attained through infra red lamps. At a wavelength of 680nm of the infra red


10/66

lamp, the heating effect starts. We are applying a wavelength of 980 nm.

This method offers following advantages over the conventional heating:

90% of energy is transmitted as infrared

Lamp lifetime 5000 hours

Instant, accurately controllable radiant heat

Easy installation

Simple, safe and clean heat source

High-efficiency, low energy costs

Apart from the heating accuracy and speed provided by the Infra Red

lamps the solid state relay also has major advantages in controlling the

temperature. Temperature in the furnace is usually controlled by a

conventional relay. But a conventional relay is said to work for only one

million operations and hence the lifetime is very less. In order to avoid this

difficulty and control the temperature for N number of operations and N

number of years, we are using a solid-state relay, which is a combination of

OPTO TRIAC and SCR connected back to back.

The entire project set up consists of the following components:

Fabricated furnace

Infra red lamp

Thermocouple

Signal conditioner

Embedded controller

Solid state relay

display


11/66

BLOCK DIAGRAM OF ENTIRE SETUP

The furnace consists of the infra red lamp which is the heat

source. The temperature of the component which is heated is measured using

a thermocouple. The output of the thermocouple is conditioned and

amplified using signal conditioning equipment. The amplified output is sent

to the controller. The controller receives the signal and displays the

temperature for the user to see. It also compares the temperature to the

required set point temperature and controls the solid state relay accordingly.

The solid state relay controls the input to the lamp in the furnace according

to the command of the controller. If the actual temperature is lesser than the

set temperature, the lam is switched ON. If the actual temperature exceeds

the required temperature then power to the infra red lamp is cut OFF.

FURNACE

FABRICATION

MODEL

THERMOCOUPLESIGNAL

CONDITIONER

SETPOINT

EMBEDDED

CONTROLLER

DISPLAY

SOLID STATE

RELAY


12/66

CHAPTER 2

DESIGN AND SPECIFICATION


13/66

FURNACE SPECIFICATION

Max. temperature : 325C.

Furnace cube material : Mild steel sheet (18 gauge).

Insulation material : Mineral wool.

Inner coating : Berger Alloy coating.

Area occupied : 1 Feet square.

Utilization area : 1 feet square.

INFRA RED LAMP SPECIFICATION

Number of lamps : 2.

Heating type : Radiation heating.

Input power : 500 watts.

Wavelength : 980 nm.

Max. Temperature : Up to 1000C.


14/66

THERMOCOUPLE SPECIFICATION

Type : K type thermocouple.

Composition : Chromel-Alumel.

Range : 0 - 1350C.

Speed : 1 microsecond

CIRCUIT SPECIFICATION

Control action : 1C.

Interface : LCD display.

Switching : Solid state relay.

A to D converter : 12- BIT Channel.

Interface : embedded controller with serial port.


15/66

CHAPTER 3

MECHANICAL DESCRIPTION


16/66

COMPONENTS USED

The main components of the furnace are as follows:

Furnace cubes

Insulator material

Furnace door

Infra red lamps

Lamp holders

Berger alloy coating

External paint

Thermocouple

FURNACE CUBES

The furnace cubes are made from mild steel sheets of thickness 18

gauge. The oven is of double walled construction, the gap between the two

walls being 50 mm. The sheets are folded and welded to form two identical

cubes. One of the cubes is made larger than the other. The inner cube is

made closed on all sides except the front. It is made to the dimensions of 1

feet cube. That is 1 feet on all sides. The outer cube is made 1 feet on all

sides. The edges are welded and the closing side of the outer cube is bolted

closed. Mild steel sheets can handle high temperatures and also form a hard

structure to the furnace.


17/66

INSULATOR MATERIAL

The insulator used in the furnace is mineral wool. This is a very

effective insulator. It is similar to glass wool but more effective. Insulator

material is packed in between the outer and inner mild steel cabins. The

insulator is loosely packed. It has very low thermal conductivity of k = 0.06

W/mk. Since the mineral wool is loosely packed, the air packets will further

increase the thermal resistance, thereby reducing the conduction losses. It

may be pointed that air is an excellent insulator having k = 0.02 W/mk.

Mineral wool is also called marganite wool. This insulator is so effective

that when the inner cabin is at a temperature of around 325C, the outer

surface of the cabin remains only slightly higher than the room temperature.

This makes this type of furnace safer and environment friendly.

FURNACE DOOR

The furnace door is made similar to the furnace cube itself. The door

is made like a hollow mild steel block by welding the mild steel plates in

that form. A gap of half an inch is maintained between the steel plates on

both sides. One side of the door is left open initially to insert the insulatormaterial. After the insulator is filled the side is closed using bolts. The door

is screwed to the furnace on one side using normal hinges and a small handle

is also provided. The door remains closed with the help of a ball-socket type

of joint. This allows the door to opened and closed easily.


18/66

POWER RATING:

The oven has a rating of 500W and can be operated on 230V, single phase,

AC supply. The maximum temperature inside the oven is restricted to 325

degree Celsius.

INFRA RED LAMP:

Industrial manufacturing processes are becoming more and morerationalized. Automation increases and production rates rise. To gain the

competitive edge, industry today demands innovative, effective heating

solutions that will optimize cost of ownership. Infrared heat is transferred

from the heat source to the object to be heated without any intermediary.

In our project we have used two Infra Red Lamps each having a

capacity of 250 Watts. They transfer heat on to component by means of

radiation heat transfer as described in the operation section of our project.

Features:

90% of energy is transmitted as infrared

Lamp lifetime 5000 hours

Instant, accurately controllable radiant heat

Easy installation


19/66

Advantages:

Precisely controllable heat delivery :

Optimum economy is achieved not only by low-cost installation, but also byhigh-efficiency heat delivery to exactly where it is needed. Low thermal

inertia of the infrared lamps means there is no delay for warming-up, and

conversely heating stops virtually instantly when the lamps are switched off.

Heat delivery is precisely controllable, either manually or by the use of an

electronic control system.

Long 5,000 hour lifetime:

Contributing further to their outstanding economy, all the Philips infrared

lamps have a long 5,000 hour lifetime.

THERMOCOUPLE

Two strips of dissimilar metals joined to form junction called

thermocouple. If the junction is heated and a milli-voltmeter is connected

across the free ends away from the junction, there will be found a voltage

present. This voltage is caused by the different work -function of the metals

forming the junction and is dependent upon both the temperature and the

types of metals used.

Since the voltage across the thermocouple junction is proportional to

temperature we may use it in thermometry. The voltage is not, however, not

linear function of temperature, and that tends to limit the application

somewhat. It is important to know over what range the thermocouples linear


20/66


21/66

It is extremely important that polarity be observed when making

connections. There is only one method of determining polarity and that is

by knowing which wire is which the wires can be identified by testing them

with a permanent magnet. Alumel is slightly magnetic; iron is strongly

magnetic, constantan not at all. Copper can be identified by its color.

K TYPE THERMOCOUPLE:

Type K (chromelalumel) is the most commonly used general purpose

thermocouple. It is inexpensive and, owing to its popularity, available in a

wide variety of probes. They are available in the 200 C to +1200 C

range. The type K was specified at a time when metallurgy was less

advanced than it is today and, consequently, characteristics vary

considerably between examples. Another potential problem arises in some

situations since one of the constituent metals, nickel, is magnetic. The

characteristic of the thermocouple undergoes a step change when a magnetic

material reaches its Curie point. This occurs for this thermocouple at 354C.

BERGER ALLOY COATING

This a special type of coating applied on the inner walls of the

furnace. It is combination of 25% paint, 35% aluminum and 40% zinc. This

provides a reflective surface for better heating and at the same time prevents

heat from escaping out. This improves the efficiency to a great extent. It is

commercially available under the brand MRF coatings.
http://en.wikipedia.org/wiki/Chromelhttp://en.wikipedia.org/wiki/Alumelhttp://en.wikipedia.org/wiki/Chromelhttp://en.wikipedia.org/wiki/Alumel


22/66

MANUFACTURING PROCESSES

Furnace fabrication involves bulk deformation processes like sheet

metal bending, deep drawing, etc. to obtain the outer casing of the furnace.

The first process is the bending of sheet using highly precise anvil, hammer

arrangement and skilled labour. The material used is 18 SWG Mild Steel

sheet. This material is strong to enough to withstand very high temperatures

and also well suited for the manufacture furnace casing. Since the material is

to be deformed to bring it to the required shape, plastic deformation and

yield criteria need to be developed upon.

Plastic deformation of a material depends upon two principal laws of

solid mechanics namely, Von Misces Theory and Guest Tresca Theory.

Both these theories give us the yielding criteria for a specimen based on

maximum shear stress and maximum normal stress respectively.

The process involves bending and deforming the sheet to the required

specifications and dimensions as given by the customer. Sheets of sizes

400mm and 300mm are made from huge cold rolled sheet to make the

furnace casing. The reason behind using cold rolled sheets is that material

undergoes heat treatment processes in cold rolling process and hence is

devoid of any porosity. The sheets are bent to the required dimensions. Once

the shaped is obtained the inner and outer casing are welded together using

clamps within the gap between the walls. The joining process used here,

welding is highly precise as any small mistake could lead to an improper

alignment of the walls. Hence a skilled labour is required to affect the


23/66

joining process. The packing of insulator also comes under the fabrication

process and they are loosely packed in the gap between the walls and the

reason for doing so is outlined in the construction section.


24/66

OPERATION

Mass production of painted components can be achieved either by dip

coating on a conveyor or spray painting using spray painting booths. After

spray painting the component has to be baked at a required temperature as

recommended by the paint manufacturer.


25/66

This being a project, the operation is intended to be carried out on

small components using a prototype oven. The initial warm-up time may be

about 30 mins to 45 mins. After this the component is placed inside the

oven. There will be a temperature drop and it may take about 10 mins for the

oven to attain the set temperature. The subsequent holding time in

conventional heating is about 20 mins to make sure that the baking has been

uniform. In Infra Red heating, because of the advantages outlined in section

it is seen that the time for baking is only 7 mins.

MECHANISM OF HEAT TRANSFER

RADIATION:

The method of heat transfer is primarily through radiation which is

governed by Stefan- Boltzmann law, Wiens law and Planck distribution

law. Radiation heat transfer is caused as a result of vibrational and rotational

movements of molecules, atoms and electrons. The energy is transported by

electromagnetic waves (photons). Radiation requires no medium for

propagation, therefore can take place also in vacuum. All matters emit

radiation as long they have a finite temperature. The rate at which radiation

energy is emitted is usually quantified by Stefan Boltzmann law:

q = AT4

Where the emissivity , is a property of the surface characterizing how

effectively the surface radiates compared to a black body.


26/66

Stefan - Boltzmann constant (W/m2 K4).

T - absolute temperature of the surface in Kelvin.

A portion of the electromagnetic radiation spectrum is shown below.

Thermal radiation lies in the range of 0.1 to 100 micro metres. It includes

ultra violet radiation, visible light and Infra Red radiation. As said above

the propagation of thermal radiation takes place in the form of discrete

quanta, each having energy of

E = h

Where h is the Plancks constant given by h = 6.625*10^-34 joule second.


27/66


28/66

The diagram shown below gives a schematic representation of the

heat transfer through the furnace wall.

From the figure shown above it is seen that the heat transfer through

the wall is very less as the slope of the temperature profile i.e. the

temperature gradient across the wall is very less.

Temperature profile

T1

b

k

T2

(dT / dx ) = (T1 T

2) / b

Mineral

wool


29/66

CHAPTER 4

ELECTRONIC DESCRIPTION


30/66

CIRCUIT EXPLANATION

Basic circuit operation starts from heating chamber. Thermocouple

will be placed inside the chamber and K type thermocouple is used and it

can withstand up to 1340 degrees. Generally any thermocouple will produce

zero emf for room temperature and produces equivalent emf in terms of

voltage for corresponding temperature.

Thermocouples are based on See beck effect and it is as follows

when two dissimilar metal joints are kept together at two different

temperatures, it produces emf. Thermocouples are active transducers whose

characteristics cannot be changed as per requirement. Some limitations are

1. It requires cold junction compensation

2. Poor sensitivity

3. Poor linearity

The above said problems can be solved using electronic circuits. To

solve cold junction we can sum room temperature by using opAmps. To

improve sensitivity, we can amplify the output of thermocouple. Using

integrators super imposed with low pass filters can solve poor linearity. We

can efficiently use electronic advantage for our project in various ways like

amplifiers, integrators, summer, current amplifier, ADC, multiplexers, PC

parallel port and power electronic solid state switching system along with

powerful C language.


31/66

In our project K type thermocouple produces

0 mv at 30 degree centigrade

2.9 mv at 100 degree centigrade

6.9 mv at 200 degree centigrade

11 mv at 300 degree centigrade

We have designed our furnace model up to 300 degree centigrade. At

300 degree centigrade, output from the thermocouple is 11 mv. 11-mv

output is amplified to 300 mv for local display and 3v for 12-bit PC coupled

ADC. To do the above work, we have used opAMPS. While designing an

opAMP for a thermocouple, some important steps must be followed:

1. It should not load the thermocouple

2. Good current output compatibility

3. Automatic room temperature compensation must be given

4. Open thermocouple protection must be there

5. While amplification, noises will also be amplified. So proper

noise rejection circuits must be designed.

6. Protection must be taken to prevent ADCs from hazardous

electrical transients.

Our design in electronics strictly covers all the above for good industrial

performance. OpAMP used is IC LM742. It has low cost and it is widely

used and is also available everywhere.


32/66

Our minimum range of temperature : 30 degree centigrade

Our maximum range of temperature : 325 degree centigrade

Minimum range is called as Zero and Maximum range will be called as

Span (Exact Instrumentation Standard)

COMPONENTS USED

The components used in the electronic control system are as follows:

1. SIGNAL CONDITIONER

1.1.Power supply unit

1.2.Step down transformer

1.3.Rectifier unit

1.4.Filtering unit

1.5.Voltage regulators

2. OPERATION AMPLIFIER

2.1.Non-inverting amplifier

2.2.Inverting amplifier

3. MICRO CONTROLLER

3.1.Architecture

3.2.Features

3.3.memory organization


33/66

SIGNAL CONDITIONER

The measured temperature, which is basically a physical quantity, is

detected by the first stage of the instrumentation or measurement system.

The first stage is the detector transducer stage. The quantity is detected and

converted or transduced in to an electrical form in most cases. The output of

the first stage has to be modified before it becomes usable and sufficient to

drive the signal indicating stage, which is the last stage. This last stage may

consist of indicating recording displaying and data processing elements. In

an electronic-aided measurement, the quantity to be measured is converted

into electrical signal and then amplified or otherwise modified to operate a

device, which displays the numerical value of measured quantity.

An input device such as a photo detector, Thermistor Bridge, glass pH

electrode or strain gauge circuit is used to convert the quantity to be

measured into electrical signal. Some characteristics of this signal is relatedin a known way to the quantity to be measured. The measured quantity is

now encoded as an electrical signal. The electrical signal from the input

device is then modified by suitable electronic circuit to make it suitable for

operating a readout device. The electronic circuit is frequently an amplifier

with the appropriate adjustable parameters and some times with automatic

compensation for non-linearity, temperature variation, etc of the input

device. The end result of any measurement is a number.


34/66

The output number is obtained from a read out device. The measured

quantity was encoded in at least three different ways. First as a physical or a

chemical quantity, second as some characteristics of electrical signal, and

finally as a number. The data encoded is called DATA DOMAIN.

The signal conditioning equipment may be required to perform linear

processes such as amplification, attenuation, integration, differentiation,

addition or subtraction. They are also required to do non-linear processes

such as modulation, demodulation, sampling, filtering, clipping and

clamping, squaring and linearising or multiplication by another function.

These functions require proper selection of components and faithful

reproduction of the final output further presentation stage. The signal

conditioning or data acquisition equipment is in many cases an excitation

and amplification system for passive transducer or an amplification system

for active transducer. In both cases, the transducer output is brought to the

required level to make it useful for conversion, processing, indicating and

recording.

Excitation is needed only for passive transducer, because they do not

generate their own voltage or current. It is essential for passive transducer

like strain gauge, potentiometers, resistance thermometers, and inductive or

capacitive transducers to be excited from an external source.

Active transducers such as thermocouples, piezo-electric crystal and

inductive pick ups etc., do not require an external excitation because their

own voltages only by the application of physical quantities. The excitation

source may be AC or DC .In a simple DC system the strain gauge


35/66

constitutes one or more arm of the Wheatstone bridge, which is excited by

the DC source. The bridge can be balanced by using a potentiometer and can

also be calibrated to indicate the unbalanced condition.

POWER SUPPLY UNIT

As we all know any invention of latest technology cannot be activated

without the source of power. So it this fast moving world we deliberately

need a proper power source which will be apt for a particular requirement.

All the electronic components starting from diode to Intel ICs only work

with a DC supply ranging from 5v to 12. We are utilizing for the same,

the cheapest and commonly available energy source of 230v-50Hz and

stepping down, rectifying, filtering and regulating the voltage.

STEP DOWN TRANSFORMER

When AC is applied to the primary winding of the power transformer

it can either be stepped down or up depending on the value of DC needed. In

our circuit the transformer of 230v/15-0-15v is used to perform the step

down operation where a 230V AC appears as 15V AC across the secondary

winding. One alteration of input causes the top of the transformer to be

positive and the bottom negative. The next alteration will temporarily cause

the reverse. The current rating of the transformer used in our project is 2A.

Apart from stepping down AC voltages, it gives isolation between the power

source and power supply circuitries.


36/66

RECTIFIER UNIT

In the power supply unit, rectification is normally achieved using a

solid-state diode. Diode has the property that will let the electron flow easily

in one direction at proper biasing condition. As AC is applied to the diode,

electrons only flow when the anode and cathode is negative. Reversing the

polarity of voltage will not permit electron flow.

A commonly used circuit for supplying large amounts of DC power is

the bridge rectifier. A bridge rectifier of four diodes (4*IN4007) are used to

achieve full wave rectification. Two diodes will conduct during the negative

cycle and the other two will conduct during the positive half cycle. The DC

voltage appearing across the output terminals of the bridge rectifier will be

somewhat lass than 90% of the applied rms value. Normally one alteration

of the input voltage will reverse the polarities. Opposite ends of the

transformer will therefore always be 180 deg out of phase with each other.

For a positive cycle, two diodes are connected to the positive voltage

at the top winding and only one diode conducts. At the same time one of the

other two diodes conducts for the negative voltage that is applied from the

bottom winding due to the forward bias for that diode. In this circuit due to

positive half cycleD1 & D2 will conduct to give 10.8v pulsating DC. The

DC output has a ripple frequency of 100Hz. Since each altercation produces

a resulting output pulse, frequency = 2*50 Hz. The output obtained is not a

pure DC and therefore filtration has to be done.


37/66

FILTERING UNIT

Filter circuit which is usually capacitor acting as a surge arrester always

follow the rectifier unit. This capacitor is also called as a decoupling

capacitor or a bypassing capacitor, is used not only to short the ripple with

frequency of 120Hz to ground but also to leave the frequency of the DC to

appear at the output. A load resistor R1 is connected so that a reference to

the ground is maintained. C1R1 is for bypassing ripples. C2R2 is used as a

low pass filter, i.e. it passes only low frequency signals and bypasses high

frequency signals. The load resistor should be 1% to 2.5% of the load.

1000f/25v : for the reduction of ripples from the pulsating.

10f/25v : for maintaining the stability of the voltage at the load side.

0.1f : for bypassing the high frequency disturbances.

VOLTAGE REGULATORS

The voltage regulators play an important role in any power supply

unit. The primary purpose of a regulator is to aid the rectifier and filter

circuit in providing a constant DC voltage to the device. Power supplies

without regulators have an inherent problem of changing DC voltage values

due to variations in the load or due to fluctuations in the AC liner voltage.

With a regulator connected to the DC output, the voltage can be maintained


38/66

within a close tolerant region of the desired output. IC7812 and 7912 is used

in this project for providing +12v and -12v DC supply.

OPERATION AMPLIFIER

An OpAmp is a Dc amplifier having a high gain, of he order of 10**4-

10**8. Such an amplifier can perform summing, integration, differentiation,

or act as comparator with suitable feedback networks. Hence these are

known as opamps. In such circuits the required response is obtained by the

application of negative feedback to a high gain Dc amplifier by means of a

component connected between input and output terminals, refer to as

operational feedback. An opamp is a Dc high gain amplifier usually

consisting of one or more cascaded differential amplifier stages.

The ideal opamp exhibits the following electrical characteristics.

Infinite voltage gain Av.

Infinite input resistance Ri, so that almost any signal source it can

drive and there is no loading of the preceding stage.

Zero output resistance Ro, so that output can drive an infinite number

of devices.

Zero output voltage when input voltage is zero.


39/66

Infinite bandwidth ,so that any frequency signal from zero to infinite

Hz can be amplified without attenuation.

The output voltage of an opamp is given as

Vo=A Vid = A(V1-V2)

Where A = voltage gain .

Vid=differential input voltage.V1=voltage at inverting terminal with respect to ground.

V2=voltage at non -inverting terminal with respect to ground.

NON-INVERTING AMPLIFIER

The amplifier is known as non-inverting amplifier when it uses

feedback and the input signal is applied to non-inverting input terminal of

the opamp. The closed loop voltage gain for a non-inverting amplifier is

A f = (1+Rf /R1)

INVERTING AMPLIFIER

The input signal is applied to the inverting terminal. The amplified

inverted output is feed back to the inverting input through the resistor Rf.


40/66

The signal feed back is proportional to the output voltage, feedback is

through Rf connected between output and inverting terminal of the

amplifier. The non -inverting terminal is grounded and the input signal is

applied to inverting terminal through resistance R1.Closed loop voltage gain

for an inverting amplifier is

Af = -(R f/R1)

MICROCONTROLLER

Process Instrumentation Controller (PIC) is enhanced version of

microcontrollers. It is an embedded controller. PIC microcontroller contains

several families. They are classified as three categories.

1. Low End Family:

It has 33 instructions. For example, PIC 12XXX

2. Mid Range Family:

It has 35 instructions. For example, PIC 16XXX

3. High End Family:

It has 77 instructions. For example, PIC 17XXX and PIC 18XXX.


41/66

ARCHITECTURE

Two types of Architecture are followed.

I). Van-Numan Architecture:

The width of address and data bus is same.

II). Haward Architecture:

The bus width of address and data may not be same. Pipelining

is possible here.

PERIPHERAL FEATURES

Microcontrollers have built-in peripherals, they are:

1. Memory

a. Program Memory (Eg. PROM, Flash memory)

b. Data Memory (Eg. RAM, EEROM)

2. I/O Ports

3. ADC

4. Timers

5. USART

6. Interrupt Controllers

7. PWM / Capture


42/66

PM DMI / O

CPU Ports

Timer /

Counter PWM/Capture

ADC

USART

OSC WDT

Port A

Port B

Port CPort D

Port E


43/66

The PIC 16C774 has five serial ports namely A, B, C, D and E. It has five

parallel ports namely:

1. PSP (Parallel Slave Port 8 bit wide)

2. SSP ( Serial Synchronous Port)

3. MSP (Master Serial Synchronous Port)

4. I2C (Inter Integrated Circuit)

5. SPI (Serial Peripheral Interface)

PIC BLOCK DIAGRAM

PIC 16C774

Analog PowerSupply

Digital PowerSupply

Crystal

Oscillator

Synchronous

Switch

Analog Ref

Voltage 5V

8 channel

Analog Input

External

USART

Logic I/O

Connector

C

pu


44/66

GENERAL FEATURES

High Performance RISC CPU: Only 35 instructions are available,

hence easy programming is possible which increase the processing

speed.

Operating Speed: 9600 baud rate

Power On Reset: Whenever the PIC is reset, the program counter

reaches the known address.

Watch Dog Timer: It is used to find Communication Error with its

own on chip RC oscillator for reliable operation.

Low Power Consumption

High Sink / Source Current: The output of the Embedded Controller

can be used to drive printer, relays, solenoid valves etc. No need of

driver circuit.

Compatible to all computer language No need of DLL (Dynamic Link

Library)


45/66

DESIGN FEATURES

Individual power supply for Analog and Digital circuits is required to

avoid drift on analog portion.

Double regulated filtered reference source is needed to ensure safest

ADC operation.

External clock source must be used which enables the user to design

the required speed.

External CPU Synchronous circuit must be designed incase of PC

requirement. Switch is used to synchronize the Embedded Controller

with the PC to get COMOK signal.

External RS-232 should be used for data conversion.

MEMORY ORGANIZATION

There are two memory blocks in PIC microcontroller. Each block

has its own bus so that concurrent access can occur.

1. Program Memory

2. Data Memory


46/66

Program Memory Organization:

PIC 77X has a 13 bit program counter capable of addressing 8k 14

program memory space. Each device has 4k 14 words of program space.

The reset vector is at 0000H

Receiving Interrupt vector is at 0004H

PIC has hardware stack with 8 bit width. It needs jump instruction to

access subroutines. Push and Pop instructions cannot be used since there is

no software stack is available.


47/66

Program memory is organized as page 0, page1 up to page3 each having

2K memories. Page address should be mentioned in PC latch for execution.


48/66

Data Memory Organization:

The data memory is partitioned into multiple banks which contain

general purpose registers and special function registers.

Bits RP1 and RP0 are bank select bits.RP1 RP0 Bank no

0 0 0

0 1 1

1 0 2

Reset Vector

Interrupt Vector

Page 0

Page 1

Page 2

Page 3

Program Counter

Stack Level 1

Stack Level 2

Stack Level 8

0000H

0000H

0004H

0005H

07FFH

0800H

0FFFH

1000H

3FFFH

}On-ChipProgram

memory

Program Memory Organization


49/66

1 1 3

Each bank extends up to 7FH (128 bytes). The lower locations of

each bank are reserved for the special function register. Above the special

function registers are General purpose registers, implemented as Static

RAM. In all banks the bottom most 16 bits are called access banks. The

data stored in these locations can be accessed irrespective of the bank

number.

CIRCUIT OPERATION

The temperature of the component is measured by a thermocouple

which works on the principle of seebeck effect.

GPR

SFR

AccessBank

00

1F

20

70

71

7F

00

1F

20

70

71

7F

00

1F

20

70

71

7F

00

1F

20

70

71

7F

GPR

SFR

AccessBank

GPR

SFR

AccessBank

GPR

SFR

AccessBank

BANK0 BANK1 BANK2 BANK3

Data Memory Organization


50/66

According to seebeck When two dissimilar metals in a circuit are

maintained at different temperatures an emf is produced in the circuit

The emf obtained can be calibrated to give the temperature of the

component.

The e.m.f induced is of small amplitude and there is no linearity. This

problem is solved by using a signal conditioner.

The signal conditioning equipment may be required to perform linear

processes such as amplification, attenuation, integration,

differentiation, addition or subtraction. They are also required to do

non linear processes such as modulation, demodulation, sampling,

filtering, clipping and clamping, squaring and linearising or

multiplication by another function.

After suitable conditioning, the signal is sent to the microcontroller.

The micro controller in a small size controller which is embedded into

the system to control the input to the furnace.

The micro controller is linked to a LCD display through an analog to

digital converter to provide interface for easier operation.

The TRIAC is a kind of transistor and SCR stands for Silicon

Controlled Rectifiers. The solid state relay is used control the power

supply to the furnace. They receive input from the micro controller.


51/66

They help in controlling the current flow to the furnace thereby

controlling the furnace temperature.

CALCULATION

Thermocouple output of 11 mv is amplified to 300 mv for local ADC

and 3000 mv for PC coupled ADC.

Local Display Gain = output / Input

= 300/11 = 27.272

PC coupled Gain = 3000/11 = 272.72

Gain required for Local Display = 27.272

Gain required for PC coupled ADC = 272.72

OpAMP 1 output is connected to Local Display

Gain calculation for OpAMP 1

OpAMP mode = Inverting summing Amplifier

Gain = - Rf / Rin

Rf = 1000 K

Rin = 33K (fixed) to 20K (variable)

Gain = 1000/53 to 1000/33

= 18.86 to 30.30


52/66

The exact gain can be tuned by adjusting VR1 multi turn

potentiometer. Now output of OpAMP A1 can be given to 3-1/2 digit

integrative ADC which produces 1 digit for 1 mv.

OpAmp 1 output is fed to input of A2 OpAmp. A2 output is fed to Pc

coupled ADC. Gain requirement of this ADC is 272.72.

OpAMP1 Gain is already tuned to - 27.272

So OpAMP A2 gain must be -10.

Gain = - Rf/Rin

= -1000/-10

= 10

Now Net Gain = A1 gain * A2 gain

= -27.272* -10

= 272.72

This output can be given to Pc coupled ADC. We have used 12-bit

ADC, whose max Vin = 10 mv. For that it produces

10 v = 4096 fractions

3v = 1228 fractions

Now we have 1228 fractions to indicate 300 degree centigrade.

Essentially we must have domain factor

Domain factor = ADC value / Actual value


53/66

= 1228 / 300

= 4.093

The data output from ADC is divided by 4.093 to indicate the actual

value of temperature.


54/66

CHAPTER 5

PROGRAMMING

FLOW CHART


55/66

ALGORITHM

STEP 1: Start the program

START

INITIALISE THESERIAL PORT

GET

SETVALUEFOR TEMP

READ TEMP

FROM LCD

CHECK

CURRENTVAL > TEMP

FURNACE ON

FURNACE OFF

NO

YES


56/66

STEP 2: Initialize the parallel port

STEP 3: Get the Set Value for Temperature

STEP 4: Read Temperature from ADC using IC 244

STEP 5: Check if the Current Value is Greater than the Set Temperature.

If yes GOTO STEP 6 elseGOTO STEP 7

STEP 6: Furnace is Switched ON

STEP 7: Furnace is Switched OFF

STEP 8: Check whether any key is pressed


STEP 9: Check whether the key pressed is released


STEP 10: Stop the program


57/66

CHAPTER 6

ADVANTAGES AND FEATURES

SOLID STATE CLOSED LOOP CONTROL


58/66

We have used power electronic circuit for obtaining heat control.

Open loop is a time domain ON/OFF control, where the expected value

cannot be controlled. So we are using closed loop control where the output

can be controlled. The set point will be compared with the actual

temperature and control action will be taken continuously and consistently.

The main disadvantage of this type of this relay is that there will be wear and

tear.

INCREASED HEATING EFFICIENCY

General electrical heater accepts electrical energy and converts into

thermal energy. This type of heaters will be a closed fabrication model. Heat

obtained will not be distributed equally to all the areas of furnace. A

circulation fan will be used to maintain constant temperature in all areas. So

efficiency will be only at 65%.

We have used infrared heating system, whose wavelength is 980 nm. If

wavelength goes above 680 nm penetration effect starts. In our heating

system, good penetration effects will be created. So the given electrical

power will be utilized very efficiently for heating and there is no need for

any circulation fan. Penetration takes place in the entire closed furnace. For

better performance, we have coated BERGER ALLOY COATING which

is a combination of 25% paint, 35% aluminum and 40% zinc. This will

provide good reflection and also improves efficiency.


59/66

SUITABILITY

We have used thermocouple for this project. Thermocouple is a

bimetallic function, made up of two different materials based on See beck

effect. Thermocouple bears International Standards coding like IS2054,

BS2054, and ANSI2054. Thermocouple has great interchangeability and no

field calibration is to be done during interchanging. We can use any

thermocouple depending on the application and range. We have used K

type thermocouple made up of Chromal and Alumal.

INTERNATIONAL COMPATABILITY

All the components and elements used in our project exactly meets the

International Standards. Thermocouple, Heating system (Infrared), Solid

State SCR control with optical insulation is globally produced. The name,

specification, manufacturers are coming under JEDEC control. JEDEC

stands for Joint Electron Devices Engineering Control. All JEDEC control

manufacturers must maintain quality of international standards.

DIRECT DIGITAL DISPLAY


60/66

General Indicating instruments need multiplication or division factors

for reading (e.g. moving coil, moving iron). In our project we have presented

the result in a very lucid manner. On line temp reading is indicated on the

LCD screen in user-friendly numerical form.

LINEARITY IMPROVEMENT

Low pass filter coupled with Integrative filter will improve linearity of non-

linear inputs. Two integrative filters and two low pass filters are used for this

purpose.

OPEN THERMOCOUPLE PROTECTION

There is no chance of short circuit in a thermocouple as it is already

short-circuited. When a thermocouple is open circuited infinite resistance

will be across ground and R1-Vr1 junction. In this case supply voltage at R1

will flow directly to A1 and the output will be infinite. If there is any chance

of infinite voltage gain, this can be sensed by software and automatically the

circuit is tripped off and open thermocouple indication is given on the PC

screen. Local display will indicate infinity on the seven-segment display.

The display will be 1 in the thousands digit and this indicates that the

thermocouple is open circuited.


61/66

SAFETY FEATURES

The circuit is designed to automatically switch of the heating element in

case the temperature crosses 325C. There is also a chance of the

thermocouple open circuiting in which case the display indicates the fault

and the heating element is switched off.

OTHER FEATURES

Controllable Output: Output can be controlled precisely to match

the temperature requirements of the process.

Directional Heating: Systems are able to selectively heat specific

regions of the part.

Clean Heating: Electric heat source is environmentally clean and

efficient.

OTHER APPLICATIONS

Some of the possible applications of this project are:


62/66

1. Drying applications.

2. Pre-heating.

3. Incubators.

4. Alternative Owen.


63/66

CONCLUSION

CONCLUSION


64/66

We have designed and fabricated a prototype of an infra red

furnace in which heat radiated from infra red lamp is used to achieve quicker

and effective heating. Thus we have developed a method to improve the

paint drying process and at the same time decrease the cost of production.

Moreover the life of the furnace and components is also increased.

The electrical circuit is also accurate and durable hence reducing the

cost of maintenance and repair which is a problem with the existing

furnaces.


65/66

BIBLIOGRAPHY

BIBLIOGRAPHY

REFERENCES:


66/66

Application of rapid infra red heating for aluminium forgings , Puja

B.Kadolkar , Hui lu, Craig A.Blue , 25th forging Industry technical

Conference, Detroit MI, April 2004.

Use of infrared heating of glass in inertialess hardening furnaces ,

Glass and Ceramics, Springer New York, December 07, 2004

Rapid Infra red preheating of extrusion die, Dr.Srinath

Vishwanathan & Dr.Peter Angelini, Material Processing group,

OakRidge National Laboratory.

US Patent Issued on June 21, 1994, Paint baking oven having a

bring-up zone utilizing short and medium wave infrared lamps

(WO/1993/005353) Paint baking Oven for Infra Red Lamps

TEXT BOOKS:

Heat Transfer , J.P.Holman, Ninth edition, Tata McGraw Hill

Publications. Heat Transfer , Yunus A. Cengel, Tata McGraw Hill Publications.

Documents

IRF - report