CD 5 Main Documentation

8/12/2019 CD 5 Main Documentation

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A PROJECT REPORT ON

TEMPERATURE CONTROL OF INFANT INCUBATOR

Project report submitted in partial fulfillment of the requirement for the

Award of the Degree of

BACHELOR OF TECHNOLOGY

IN

BIOMEDICAL ENGINEERING

By

N NIHARIKA 09241A1112P APARNA S SRUTHI 09241A1124

Under the guidance of

Mrs. S.BHARGAVI

Assistant Professor

DEPARTMENT OF BIOMEDICAL ENGINEERING

GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING &

TECHNOLOGY

BACHUPALLY, HYDERABAD 500090


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2009-2013

GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING & TECHNOLOGY

Hyderabad, Andhra Pradesh.

DEPARTMENT OF BIOMEDICAL ENGINEERING

C E R T I F I C A T E

This is to certify that the project report entitled TEMPERATURE CONTROL OF INFANT

INCUBATOR that is being submitted by N NIHARIKA and P APARNA S SRUTHI in partial

fulfillment for the award of the Degree of Bachelor of Technology in BIOMEDICAL ENGINEERING

to the Jawaharlal Nehru Technological University as a record of bonafide work carried out by them undermy supervision. The results embodied in this project report have not been submitted to any other

University or Institute for the award of any graduation degree.

Prof. T. PADMA Mrs. S. BHARGAVI

HOD, BME Assistant Professor, Internal guide

GRIET, Hyderabad GRIET, Hyderabad

External Examiner


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ABSTRACT

Temperature plays an important part in our environment. Changes in temperature can

affect the behavior of human beings, plants and even materials such as semiconductors. This

project is to control the temperature of a given environment such as baby incubator.

Incubators provide warmth and prevent heat loss to significantly improve survival

rates. The use of air-heated incubators has been the standard method of providing a stable,

individualized thermal environment for the newborn infant at risk.

A microcontroller is used to control the temperature in a baby incubator Where the

temperature had to be kept constant at 36.90C as in mothers womb. The system will function as

stated in the programming code of Aurduino in order to keep the temperature stable. A simpletemperature controller which has least complex circuitry has to be designed so that it saves space

and be more reliable for an incubator. Present design which uses microprocessor as main

controller in digital signal processing combined with complex combinational logic circuit are

redundant and needs to be improved in the sense of functionality. Hence, replacement of

microcontroller with an Aurduino microcontroller is prudent action due to its efficiency and

reliability especially in an incubator Where the life of an infant relies on.


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CONTENTSCHAPTER 1 ................................................................... Error! Bookmark not defined.

1.1 INFANT THERMOREGULATION ................. Error! Bookmark not defined.

CHAPTER 2 ................................................................... Error! Bookmark not defined.

2.1 OVERVIEW .......................................................... Error! Bookmark not defined.

2.2 PROBLEM STATEMENT .................................... Error! Bookmark not defined.

2.3 NEEDS FOR INCUBATION ................................ Error! Bookmark not defined.

2.4 OBJECTIVE ..........................................................Error! Bookmark not defined.

2.5 STEPS INVOLVED .............................................. Error! Bookmark not defined.


3.1 ACRYLIC SHEET ................................................ Error! Bookmark not defined.3.1.1 Expansion and Contraction .............................. Error! Bookmark not defined.

3.1.2 Flexibility ........................................................ Error! Bookmark not defined.

3.1.3 Chemical Resistance ........................................ Error! Bookmark not defined.

3.1.4 Electrical Properties ........................................ Error! Bookmark not defined.

3.1.5 Light Transmission .......................................... Error! Bookmark not defined.

3.1.6 UV Light Resistance ....................................... Error! Bookmark not defined.

3.1.7 Optical Clarity .................................................Error! Bookmark not defined.

3.1.8 Weather Resistance ......................................... Error! Bookmark not defined.

3.1.9 Safety .............................................................. Error! Bookmark not defined.

3.1.10 Light Weight ................................................. Error! Bookmark not defined.

3.2 COMPARTMENT DESCRIPTION ......................... Error! Bookmark not defined.

3.2.1 Compartment A ...............................................Error! Bookmark not defined.

3.2.1.1 Heating unit .................................................. Error! Bookmark not defined.

3.2.1.2 Cooling unit.................................................. Error! Bookmark not defined.

3.2.2 Compartment B ............................................... Error! Bookmark not defined.


4.1 SENSING THE TEMPERATURE......................... Error! Bookmark not defined.

4.1.1 Thermistor ....................................................... Error! Bookmark not defined.

4.2 READING THE TEMPERATURE ....................... Error! Bookmark not defined.


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4.3 TEMPERATURE CONTROL ............................... Error! Bookmark not defined.

4.3.1 Relay ............................................................... Error! Bookmark not defined.

4.3.1.1 Basic design and operation ........................... Error! Bookmark not defined.

4.3.2 Power supply +12 Volts ................................. Error! Bookmark not defined.

4.3.2.1 Center tapped transformer ............................ Error! Bookmark not defined.

4.3.2.2 Volts center tapped ....................................... Error! Bookmark not defined.

4.3.2.3 Linear regulator ............................................ Error! Bookmark not defined.

4.3.2.4 Step transformer ........................................... Error! Bookmark not defined.

4.3.2.5 Step-down transformer consideration ............ Error! Bookmark not defined.

4.3.3 Aurduino Uno kit ............................................ Error! Bookmark not defined.


5.1 PROGRAM FOR TEMPERATURE READING AND CONTROLError! Bookmark not

defined.

5.2 FLOW CHART ..................................................... Error! Bookmark not defined.

CONCLUSION ............................................................... Error! Bookmark not defined.

RESULT ......................................................................... Error! Bookmark not defined.

FUTURE SCOPE............................................................ Error! Bookmark not defined.

REFERENCES: .............................................................. Error! Bookmark not defined.


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LIST OF FIGURES

Figure 3.1 Incubation chamber ........................................ Error! Bookmark not defined.

Figure 3.2 Acrylic sheet .................................................. Error! Bookmark not defined.

Figure 3.3 Chamber showing two compartments. ............ Error! Bookmark not defined.

Figure 3.4 Compartment A .............................................. Error! Bookmark not defined.

Figure 3.5 Compartment B .............................................. Error! Bookmark not defined.

Figure 4.1Thermistors ..................................................... Error! Bookmark not defined.

Figure 4.2 Resistance characteristics with temperature. ... Error! Bookmark not defined.

Figure4.3 Circuit for temperature sensing. ....................... Error! Bookmark not defined.

Figure 4.4 Circuit for Temperature Control. .................... Error! Bookmark not defined.

Figure 4.5 DC power Supply +12 volts circuit ................ Error! Bookmark not defined.

Figure 4.6 PCB for DC power Supply +12 volts .............. Error! Bookmark not defined.

Figure 4.6 Step down Transformer .................................. Error! Bookmark not defined.

Figure 4.7 Aurduino Uno ................................................ Error! Bookmark not defined.

Figure 5.1 Flowchart for temperature sensing and control Error! Bookmark not defined.


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CHAPTER 1

INTRODUCTION

Of the four million babies worldwide who die in the first month of life, one million die on

their first day. Preterm birth is attributed, either directly or indirectly, to at least 25 percent ofneonatal deaths, and low birth weight (LBW) newborns are at the greatest risk. About half of the

worldwide total, or 1.8 million babies each year, die for lack of a consistent heat until they have

the body fat and metabolic rate to stay warm. The current recommended method of providing

infant temperature regulation in resource constrained settings is Kangaroo Mother Care (KMC),

the practice of placing newborns directly onto the mother's chest. KMC has demonstrated

benefits in terms of improved weight gain for preterm infants, earlier hospital discharge and

higher breast feeding rates. At the same time, KMC also has important limitations:

If the mother either dies in childbirth (as one of the 529,000 maternal deaths annuallyworldwide), or is too ill after delivery, mother is unable to provide KMC.

The majority of mothers have other obligations that prevent them from being able toprovide continuous KMC, such as other children and/or a job to which they must attend.

If no one else is able to provide KMC, a baby sent home for this care may receive it

inconsistently at best and therefore suffer the complications of hypothermia, including

respiratory distress, acidosis, hypoglycemia and even death.

Skin to skin contact is considered a culturally inappropriate violation of privacy in someareas that rely on KMC.

As a consequence, at risk newborns in developing countries need a warm, clean

environment in which to grow stronger. Incubators can help provide millions of at risk infants

with shorter hospitals stays and can enable infants who might otherwise have faced a lifetime of

severe disability to experience active lives.

1.1INFANT THERMOREGULATION

Thermoregulation is a critical physiological function that is closely associated with the

neonates survival. Extremely low birth weight infants have inefficient thermoregulation due to

immaturity and care giver procedures such as umbilical line insertions, intubations, and chest x-

rays can lead to heat loss as well. As a result, infants may exhibit cold body temperatures after


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birth and during their first 12 hours of life. Thermoregulation plays a unique and crucial role in

the nurturing and development of neonates. It helps neonatal care practitioners to provide a

balanced environment through the management of temperature.

As a result of a high body surface area to body weight ratio, decreased brown fat stores, non

keratinized skin, and decreased glycogen supply, infants with extremely low birth weight

(ELBW) are particularly susceptible to heat loss immediately after birth. Hypothermia may result

in hypoglycimea, apnea, and metabolic acidosis.

Heat loss can occur in infants with extremely low birth weight in following ways:

a) Conduction: The transfer of energy from the molecules of a body to the molecules of asolid object in contact with the body, resulting in heat loss.

b) Convection: The similar loss of thermal energy to an adjacent gas.c) Evaporation: Evaporative heat loss is the total heat transfer by energy carrying water

molecules from the skin and respiratory tract to the drier environment.

d) Radiation: Radiant loss is the net rate of heat loss from the body to environmentalsurfaces not in contact with the body.

Extremely preterm infants are especially prone to these losses secondary to the poor barrier

provided by their thin, poorly keratinized skin. Normal body temperature is maintained by

balancing heat loss and heat gain in a changing environment. Less than 1C separates a baby

from cold stress and warm stress which divert energy away from growth and towards the

struggle of regulating body temperature.

The importance of maintaining the temperature of the newborn baby has been known for

centuries. Thermal stress has been associated with an increase in morbidity and mortality,

making early detection an important part of monitoring in sick infants.

Temperature control is paramount to survival and is typically achieved with use of radiant

warmers or double walled incubators. Hypothermia (< 35C) has been associated with poor

outcome, including chronic oxygen dependency. Immediately after birth, the infant should be

dried and placed on a radiant warmer.


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CHAPTER 2

DESIGN APPROACH

2.1 OVERVIEW

This project is to design a temperature controller to be used to control the temperature of

a small environment such as a baby incubator. A baby incubator is an infant stimulating system

used for intensive care of the newborn, premature or sick baby. It provides a safe and clean

environment, which has fresh air, clean and sterile ambient conditions for the babies. Usually the

controller used in the baby incubator is a Microprocessor.

2.2 PROBLEM STATEMENT

Premature or tiny babies are unable to keep themselves sufficiently warm. They are alsovery weak and prone to infections. An incubator is a special type of a coat which provides an

ideal environment for the baby. It tries to stimulate the conditions as inside the mothers womb.

2.3 NEEDS FOR INCUBATION

Temperature regulation is one of the most important factors affecting survival innewborn

infants. Infants typically lose heat to their environment in four different ways: through

conduction, convection, radiation, and evaporation. Premature infants, as compared to term

infants, are at an even greater disadvantage in temperature maintenance, because of the larger

skin surface area to body mass ratio, decreased subcutaneous fat, and low supplies of brown fat.

Furthermore, the normal surge in metabolic rate that occurs after birth is reduced in preterm

infants, resulting in limited heat production. Preterm infants birth rates are especially high in

developing countries. A combination of poor facilities, poor after birth care and a lack of

knowledge have propelled preterm birth to be one of the leading causes of infant mortality in

developing countries.

Incubators provide warmth and prevent heat loss to significantly improve survival rates.

The use of air-heated incubators has been the standard method of providing a stable,

individualized thermal environment for the newborn infant at risk. One of the very first

incubators invented by Stephane Tarnier in the late 19th century, reportedly reduced mortality

among infants with birth weights between 1200 and 2000 g from 66% to 38%. The availability


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of incubators and radiant warmers in industrialized countries has made neonatal hypothermia

uncommon, except in infants transported over long distances.

2.4 OBJECTIVE

The main objective of this project is to design a baby incubator with temperature control

using Aurduino Microcontroller, while monitoring the incubator temperature.

2.5 STEPS INVOLVED

Search for information related to required environment, for example the size of the babyincubator, function of the incubator and any information related to this project.

Search for the material and equipment required for this project.

Build an incubator that is suitable and functions almost the same as available incubator.This may require some research at the hospital.

Design the Aurduino Microcontroller programming code according to the specification oftemperature control in C language.

Design the temperature control circuit using Aurduino software. Program the microcontroller according to the specifications of the temperature control

system. Construct the circuit and build the model of incubator that is suitable for this

environment.


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CHAPTER 3

CONSTRUCTION

The chamber of the infant incubator is transparent. The chamber has two compartments a

larger and smaller compartment. The smaller compartment (compartment A) consist of thetemperature controlling unit and the larger compartment (compartment B) consist of the mattress

where the infant is kept. The chamber is constructed in such a way that the baby is kept away

from the temperature controlling part so the baby is assured to be safe. The entire chamber is

constructed using Acrylic sheets. Acrylic is chosen because it is more advantageous over Glass

and Plastic.

Figure 3.1 Incubation chamber


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3.1 ACRYLIC SHEETCast acrylic sheet is a material with unique physical properties and performance

characteristics. It weighs half as much as the finest optical glass, yet is equal to it inclarity and is

up to 17 times more impact resistant. Cast acrylic sheet is made in over 250 colors, in

thicknesses from .030" to 4.25'' and can transmit ultraviolet light or filter it out as required.

Figure 3.2 Acrylic sheet

Aircraft manufacturers use Cast Acrylic sheet in jets and helicopters. Because of its light and

energy transmission properties architects find Cast acrylic sheet ideal for skylights, sun screens,

fascia panels and dome structures.

3.1.1Expansion and Contraction

Cast acrylic sheet responds to temperature changes by expanding or contracting at a far

greater rate than glass.

3.1.2 Flexibility

Cast acrylic sheet is much more flexible than glass or many other building materials.

3.1.3 Chemical Resistance

Cast acrylic sheet has excellent resistance to attack by many chemicals. It is affected, in

varying degrees, by benzene, toluene, carbon tetrachloride, ethyl and methyl alcohol, lacquer

thinners, ethers, ketones and esters.

3.1.4 Electrical Properties

Cast acrylic sheet is an excellent insulator. Its surface resistivity is higher than that of

most plastics.


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3.1.5 Light Transmission

Colorless Cast acrylic sheet has a light transmittance of 92%. It is clearer than window

glass and will not turn yellow. Cast acrylic sheet is also available in a large variety of transparent

and translucent colors.

3.1.6 UV Light Resistance

Clear acrylic sheet resists ultraviolet light degradation. Each acrylic sheet has a ten-year-

limited warranty against yellowing and loss of light transmission.

3.1.7 Optical Clarity

Acrylic sheets have excellent light transmission. Clearer than glass. Will not yellow after

prolonged sun exposure.

3.1.8 Weather Resistance

Despite heat, cold, sunlight, and humidity acrylic sheet maintains its original appearanceand color.

3.1.9 Safety

Shatter-resistant, earthquake safe and burglar-resistant.

3.1.10 Light Weight

Even with its strength and durability, acrylic sheet is only half the weight of glass. The

two compartments compartment A and compartment B are separated from each other. A

detailed description of the two compartments are given below.


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3.2 COMPARTMENT DESCRIPTION

Figure 3.3 Chamber showing two compartments.

3.2.1 Compartment A

The compartment A consists of the temperature controlling unit which holds a heating

and cooling system.

The compartment A is again divided in to two sections:

a) The heating unit.

b) The cooling unit.


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Figure 3.4 Compartment A

3.2.1.1 Heating unit

It consists of a 100 watts bulb which is controlled by an Aurduino Microcontroller. The

bulb is given 120 volts using a step down transformer so that the baby is assured safe. A fan

which is continuously working is placed infront of the bulb with an opening to the compartment

B in such a way that the warm air is forced towards the compartment B.

3.2.1.2 Cooling unit

It consists of an Aluminum vessel filled with ice. This unit is aimed to cool the system

when the temperature goes beyond 37oC. A reliable opening is made between the ice box and

the compartment B to help cooling of compartment B. Even the fan in the Heating unit also helps

in cooling.The heating unit and the cooling unit work in such a way that the temperature in the

compartment B is maintained at a constant temperature.


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3.2.2 Compartment B

It consists of a mattress where the Infant is kept. It is provided with proper ventilation.

The chamber is provided with doors one on the top and other infront, so that the chamber can be

opened and closed according to the convenience over the take care (The person who cares the

infant).

Figure 3.5 Compartment B


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CHAPTER 4

TEMPERATURE SENSING AND CONTROL

The temperature in the chamber need to sensed and read before controlling it. A sensor is

placed in the compartment B where the baby is kept and the sensed temperature is given to the

Aurduino Uno Microcontroller.

4.1 SENSING THE TEMPERATURE

The temperature is sensed using a Thermistor.

4.1.1 Thermistor

Thermistors are inexpensive, easily obtainable temperature sensors. They are easy to use

and adaptable. They respond quickly. Circuits with thermistors can have reasonable out voltages

not the millivolt outputs thermocouples have. Because of these qualities, thermistors are widely

used for simple temperature measurements. They are not used for high temperatures, but in the

temperature ranges where they work they are widely used.

Figure 4.1Thermistors

Thermistors are temperature sensitive resistors. All resistors vary with temperature, but

thermistors are constructed of semiconductor material with a resistivity that is especially

sensitive to temperature. However, unlike most other resistive devices, the resistance of a

thermistor decreases with increasing temperature. That's due to the properties of the


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semiconductor material that the thermistor is made from. For some, that may be counterintuitive,

but it is correct. Here is a graph of resistance as a function of temperature for a typical

thermistor. Notice how the resistance drops from 100 kW, to a very small value in a range

around room temperature. Not only is the resistance change in the opposite direction from what

you expect, but the magnitude of the percentage resistance change is substantial.

Figure 4.2 Resistance characteristics with temperature.

4.2 READING THE TEMPERATURE


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The temperature sensed by the Thermistor is given to Aurduino Uno which is connected

to a laptop/Computer. A program is written and uploaded to the Aurduino which makes the

temperature to be displayed on the monitor in volts i.e.3.1 volts equal to 31oC, 3.2 volts equal to

32oC and so on. The programming part is discussed in the coming unit.

The connections given to Aurduino Uno is shown in figure 4.3 below

Figure 4.3 Circuit for temperature sensing

4.3 TEMPERATURE CONTROL

Aurduino Uno is the controller used here. The program is written to control the bulb.

when the temperature in the chamber falls down below 37 o

C the bulb glows and whenever the

temperature in the chamber goes beyond 37 o

C the bulb automatically switch off. An icebox

placed in the compartment A helps in cooling the chamber if the temperature goes beyond the

required temperature.


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The circuit is given below:

Figure 4.4 Circuit for Temperature Control.

The Relay here acts as a switch and 12 V DC supply is given to the Relay. The Step

down transformer here transforms the 230 V power supply to 120 V.

4.3.1 Relay

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism mechanically, but other operating principles are also used. Relays are used

where it is necessary to control a circuit by a low power signal (with complete electrical isolation

between control and controlled circuits), or where several circuits must be controlled by one

signal. The first relays were used in long distance telegraph circuits, repeating the signal coming

in from one circuit and re-transmitting it to another. Relays were used extensively in telephone

exchanges and early computers to perform logical operations.


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A type of relay that can handle the high power required to directly control an electric

motor or other loads is called a contactor. Solid-state relays control power circuits with no

moving parts, instead using a semiconductor device to perform switching. Relays with calibrated

operating characteristics and sometimes multiple operating coils are used to protect electrical

circuits from overload or faults in modern electric power systems these functions are performed

by digital instruments still called "protective relays".

4.3.1.1 Basic design and operation

A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core,

an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature,

and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to

the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a

spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this

condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open.

Other relays may have more or fewer sets of contacts depending on their function. The relay in

the picture also has a wire connecting the armature to the yoke. This ensures continuity of the

circuit between the moving contacts on the armature, and the circuit track on the printed circuit

board (PCB) via the yoke, which is soldered to the PCB.

When an electric current is passed through the coil it generates a magnetic field that

activates the armature and the consequent movement of the movable contacts either makes or

breaks (depending upon construction) a connection with a fixed contact. If the set of contacts

was closed when the relay was de-energized, then the movement opens the contacts and breaks

the connection, and vice versa if the contacts were open. When the current to the coil is switched

off, the armature is returned by a force, approximately half as strong as the magnetic force, to its

relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in

industrial motor starters. Most relays are manufactured to operate quickly. In a low voltage

application this reduces noise in a high voltage or current application it reduces arcing.

When the coil is energized with direct current, a diode is often placed across the coil to

dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise

generate a voltage spike dangerous to semiconductor circuit components. Some automotive

relays include a diode inside the relay case. Alternatively, a contact protection network

consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil


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is designed to be energized with alternating current (AC), a small copper "shading ring" can be

crimped to the end of the solenoid, creating a small out-of-phase current which increases the

minimum pull on the armature during the AC cycle.

A solid-state relay uses a thyristor or other solid-state switching device, activated by the

control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-

emitting diode (LED) coupled with a photo transistor) can be used to isolate control and

controlled circuits.

4.3.2 Power supply +12 Volts

Figure 4.5 DC power Supply +12 volts circuit

For the operation of relays 12V DC supply is required to excite them. So there is a need

of 12V DC power supply. This can get from the circuit shown in Fig 4.5. The main components

of this circuit are, a 230 to (18-0-18) step down transformer, bridge rectifier, capacitors and

voltage regulator (LM7812 ).


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Figure 4.6 PCB for DC power Supply +12 volts

4.3.2.1 Center tapped transformer

In electronics, a center tap is a contact made to a point halfway along a winding of a

transformer or inductor, or along the element of a resistor or a potentiometer. Taps are

sometimes used on inductors for the coupling of signals, and may not necessarily be at the half

way point, but rather, closer to one end. A common application of this is in the Hartley oscillator.

Inductors with taps also permit the transformation of the amplitude of alternating current (AC)

voltages for the purpose of power conversion, in which case, they are referred to as

autotransformers, since there is only one winding. An example of an autotransformer is an

automobile ignition coil. Potentiometer tapping provides one or more connections along the

device's element, along with the usual connections at each of the two ends of the element, and

the slider connection. Potentiometer taps allow for circuit functions that would otherwise not be

available with the usual construction of just the two end connections and one slider connection.

In a rectifier, a center tapped transformer and two diodes can form a full-wave rectifier that

allows both half cycles of the AC waveform to contribute to the direct current, making it

smoother than a half wave rectifier. This form of circuit saves on rectifier diodes compared to a

diode bridge, but has poorer utilization of the transformer windings. Center-tapped two diode

rectifiers were a common feature of power supplies in vacuum tube equipment. Modern

semiconductor diodes are low cost and compact so usually a four-diode bridge is used (up to a

few hundred watts total output) which produces the same quality of DC as the center tapped


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configuration with a more compact and cheaper power transformer. Center tapped configurations

may still be used in high current applications, such as large automotive battery chargers, where

the extra transformer cost is offset by less costly rectifiers. Center tapped transformers are also

used for dual voltage power supplies. When a center tapped transformer is combined with a four

diode type bridge rectifier, it is possible to produce a positive and a negative voltage with

respect to a ground at the tap. Dual voltage supplies are important for all sorts of electronics

equipment. In early vacuum tube audio amplifiers, center tapped transformers were sometimes

used as the phase inverter to drive the two output tubes of a push pull stage. This technique was

carried over into transistor designs also, part of the reason for which was that capacitors were

large, expensive and unreliable. However, capacitors have become vastly smaller, cheaper and

more reliable, whereas transformers are still relatively expensive. Furthermore, as designers

acquired more experience with transistors, they stopped trying to treat them like tubes. Coupling

a class A intermediate amplification stage to a class AB power stage using a transformer doesn't

make sense anymore even in small systems powered from a single-voltage supply. Modern

higher end equipment is based on dual supply designs which eliminates coupling. It is possible

for an amplifier, from the input all the way to the loudspeaker, to be DC coupled without any

capacitance or inductance. In vacuum tube amplifiers, center tapped transformers are used to

couple a push pull output stage to the speaker. This use is still relevant today because tubes and

tube amplifiers continue to be produced for niche markets. In analog telecommunications

systems center tapped transformers can be used to provide a DC path around an AC coupled

amplifier for signaling purposes. The center tapped rectifiers are preferred to the full bridge

rectifier when the output DC current is high and the output voltage is low. Phantom power can be

supplied to a condenser microphone using center tap transformers. One method, called "direct

center tap" uses two center tap transformers, one at the microphone body and one at the

microphone preamp. Filtered DC voltage is connected to the microphone preamp center tap, and

the microphone body center tap is grounded through the cable shield. The second method uses

the same center tap transformer topology at the microphone body, but at the microphone preamp,

a matched pair of resistors spanning the signal lines in series creates an "artificial center tap".


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4.3.2.2 Volts center tapped

Volts center tapped (VCT) describes the voltage output of a center tapped transformer.

For example, A 24 VCT transformer will measure 24 VAC across the outer two taps (winding as

a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC

supplies are 180 degrees out of phase with each other, thus making it easy to derive positive and

negative 12 volt DC power supplies from them.

4.3.2.3 Linear regulator

In electronics, a linear regulator is a system used to maintain a steady voltage. The

resistance of the regulator varies in accordance with the load resulting in a constant output

voltage. The regulating device is made to act like a variable resistor, continuously adjusting a

voltage divider network to maintain a constant output voltage, and continually dissipating the

difference between the input and regulated voltages as waste heat. By contrast, a switching

regulator uses an active device that switches on and off to maintain an average value of output.

Because the regulated voltage of a linear regulator must always be lower than input voltage,

efficiency is limited and the input voltage must be high enough to always allow the active device

to drop some voltage.

Linear regulators may place the regulating device between the source and the regulated

load (a series regulator), or may place the regulating device in parallel with the load (shuntregulator). Simple linear regulators may only contain a Zener diode and a series resistor more

complicated regulators include separate stages of voltage reference, error amplifier and power

pass element. Because a linear voltage regulator is a common element of many devices,

integrated circuit regulators are very common linear regulators may also be made up of

assemblies of discrete solid state or vacuum tube components.

The transistor (or other device) is used as one half of a potential divider to establish the

regulated output voltage. The output voltage is compared to a reference voltage to produce a

control signal to the transistor which will drive its gate or base. With negative feedback and good

choice of compensation, the output voltage is kept reasonably constant. Linear regulators are

often inefficient: since the transistor is acting like a resistor, it will waste electrical energy by

converting it to heat. In fact, the power loss due to heating in the transistor is the current times

the voltage dropped across the transistor. The same function can often be performed much more


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efficiently by a switched mode power supply, but a linear regulator may be preferred for light

loads or where the desired output voltage approaches the source voltage. In these cases, the

linear regulator may dissipate less power than a switcher. The linear regulator also has the

advantage of not requiring magnetic devices (inductors or transformers) which can be relatively

expensive or bulky, being often of simpler design, and being quieter.

Linear regulators exist in two basic forms:

(i) Series regulators.

(ii) Shunt regulators.

Series regulators are the more common form. The series regulator works by providing a

path from the supply voltage to the load through a variable resistance (the main transistor is in

the "top half" of the voltage divider). The power dissipated by the regulating device is equal to

the power supply output current times the voltage drop in the regulating device.

The shunt regulator works by providing a path from the supply voltage to ground through

a variable resistance (the main transistor is in the "bottom half" of the voltage divider). The

current through the shunt regulator is diverted away from the load and flows uselessly to ground,

making this form even less efficient than the series regulator. It is, however, simpler, sometimes

consisting of just a voltage-reference diode, and is used in very low-powered circuits where the

wasted current is too small to be of concern. This form is very common for voltage referencecircuit.

All linear regulators require an input voltage at least some minimum amount higher than

the desired output voltage. That minimum amount is called the dropout voltage. A common

regulator such as the 7805 has an output voltage of 5V, but it can only maintain this if the input

voltage remains above about 7V, before the output voltage begins sagging below the rated

output. Its dropout voltage is therefore 7V - 5V = 2V. When the supply voltage is less than about

2V above the desired output voltage, as is the case in low voltage microprocessor powersupplies, so called low dropout regulators (LDOs) must be used.

When the output regulated voltage must be higher than the available input voltage, no

linear regulator will work, (not even a Low dropout regulator). In this situation, a switching

regulator of the "boost" type must be used.


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4.3.2.4 Step transformer

Step down transformer is one whose secondary voltage is less than its primary voltage. It

is designed to reduce the voltage from the primary winding to the secondary winding. This kind

of transformer steps down the voltage applied to it.

As a step down unit, the transformer converts high-voltage, low-current power into low-

voltage, high-current power. The larger-gauge wire used in the secondary winding is necessary

due to the increase in current. The primary winding, which doesnt have to conduct as much

current, may be made of smaller gauge wire.

4.3.2.5 Step-down transformer consideration

Figure 4.6 Step down Transformer

It is possible to operate either of these transformer types backwards (powering the

secondary winding with an AC source and letting the primary winding power a load) to performthe opposite function a step up can function as a step down and vice versa. One convention used

in the electric power industry is the use of H designations for the higher voltage winding (the

primary winding in a step down unit, the secondary winding in a step-up) and X designations

for the lower voltage winding.

One of the most important considerations to increase transformer efficiency and reduce

heat is choosing the metal type of the windings. Copper windings are much more efficient than

aluminum and many other winding metal choices, but it also costs more. Transformers with

copper windings cost more to purchase initially, but save on electrical cost over time as the

efficiency more than makes up for the initial cost.


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4.3.3 Aurduino Uno kit

Aurduino is an open source electronics prototyping platform based on flexible, easy to

use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in

creating interactive objects or environments.

Aurduino can sense the environment by receiving input from a variety of sensors and can

affect its surroundings by controlling lights, motors, and other actuators. The microcontroller on

the board is programmed using the Aurduino programming language (based on Wiring) and the

Aurduino development environment (based on Processing). Aurduino projects can be stand alone

or they can communicate with software running on a computer (e.g. Flash, Processing and Max

MSP).

Aurduino boards can be purchased pre assembled or do it oneself kits. Hardware design

information is available for those who would like to assemble an Aurduino by hand. There are

sixteen official Aurduino that have been commercially produced to date.

The Aurduino Uno is a microcontroller board based on the AT mega328 (datasheet). It

has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a

16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button.

It contains everything needed to support the microcontroller simply connect it to a computer with

a USB cable or power it with a AC to DC adapter or battery to get started.

The Uno differs from all preceding boards in that it does not use the FTDI USB to serial

driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version R2) programmed as

a USB-to-serial converter. Revision 2 of the Uno board has a resistor pulling the 8U2 HWB line

to ground, making it easier to put into DFU mode. Revision 3 of the board has the following new

features:

1.0 pin out: added SDA and SCL pins that are near to the AREF pin and two other newpins placed near to the RESET pin, the IOREF that allow the shields to adapt to the

voltage provided from the board. In future, shields will be compatible both with the board

that uses the AVR, which operate with 5V and with the Aurduino Uno that operate with

3.3V. The second one is a not connected pin that is reserved for future purposes.


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Stronger RESET circuit. At mega 16U2 replace the 8U2.

The Aurduino Uno can be powered via the USB connection or with an external power

supply. The power source is selected automatically. External (non-USB) power can come

either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by

plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can

be inserted in the Ground and Vinpin headers of the POWER connector.

Figure 4.7 Aurduino Uno

Power

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V,

however, the 5V pin may supply less than five volts and the board may be unstable. If using

more than 12V, the voltage regulator may overheat and damage the board. The recommended

range is 7 to 12 volts. The power pins are as follows:

VIN:The input voltage to the Aurduino board when it's using an external power source(as opposed to 5 volts from the USB connection or other regulated power source). You


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can supply voltage through this pin, or, if supplying voltage via the power jack, access it

through this pin.

5V: This pin outputs a regulated 5V from the regulator on the board. The board can besupplied with power either from the DC power jack (7 - 12V), the USB connector (5V),

or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses

the regulator, and can damage your board. We don't advise it.

3V3:A 3.3 volt supply generated by the on-board regulator. Maximum current draw is50mA.

GND.Ground pins.Memory

The ATmega328 has 32 KB (with 0.5 KB used for the boot loader). It also has 2 KB of

SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Input and Output

Each of the 14 digital pins on the Uno can be used as an input or output, using pinMode, digital Write, and digital Read functions. They operate at 5 volts. Each pin can provide orreceive a maximum of 40mA and has an internal pull up resistor (disconnected by default) of 20-

50 K ohms. In addition, some pins have specialized functions:

Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data.These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL

Serial chip.

External Interrupts: 2 and 3.These pins can be configured to trigger an interrupt on alow value, a rising or falling edge, or a change in value. See the attach Interrupt

() function for details.

PWM: 3, 5, 6, 9, 10, and 11.Provide 8-bit PWM output with the analog Write function. SPI: 10(SS), 11(MOSI), 12(MISO) and 13(SCK).These pins support SPI

communication using the SPI library.

LED: 13. There is a built in LED connected to digital pin 13. When the pin is HIGHvalue, the LED is on, when the pin is LOW, it's off.


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The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of

resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is

it possible to change the upper end of their range using the AREF pin and the analog Reference

function. Additionally, some pins have specialized functionality:

TWI: A4 or SDA pin and A5 or SCL pin.Support TWI communication using the Wirelibrary.

There are a couple of other pins on the board:

AREF.Reference voltage for the analog inputs. Used with analog Reference. Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset

button to shields which block the one on the board.

The Aurduino Uno has a number of facilities for communicating with a computer,

another Aurduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial

communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the

board channels this serial communication over USB and appears as a virtual com port to

software on the computer. The '16U2 firmware uses the standard USB COM drivers, and no

external driver is needed. However on Windows, a .inf file is required. The Aurduino software

includes a serial monitor which allows simple textual data to be sent to and from the Aurduino

board. The RX and TX LEDs on the board will flash when data is being transmitted via the USB

to serial chip and USB connection to the computer (but not for serial communication on pins 0

and 1).

A Software Serial library allows for serial communication on any of the Uno's digital

pins. The ATmega328 also supports I2C (TWI) and SPI communication. The Arduino software

includes a Wire library to simplify use of the I2C bus.


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CHAPTER 5

PROGRAMMING FOR AURDUINO

The Aurduino Uno is a cross platform application written in Java, and is derived from the

Uno for the Processing programming language and the Wiring project. It is designed to introduceprogramming to artists and other newcomers unfamiliar with software development. It includes a

code editor with features such as syntax high lighting, brace matching, and automatic

indentation, and is also capable of compiling and uploading programs to the board with a single

click. There is typically no need to edit make files or run programs on a command line interface.

Although building on command line is possible if required with some third-party tools.

The Aurduino Uno comes with a C/C++ library called "Wiring" (from the project of the same

name), which makes many common input/output operations much easier. Aurduino programs arewritten in C/C++, although users only need define two functions to make a run able program:

setup( ) a function run once at the start of a program that can initialize settings loop( ) a function called repeatedly until the board powers offIt is a feature of most Aurduino boards that they have an LED and load resistor connected

between pin 13 and ground, a convenient feature for many simple tests. The above code would

not be seen by a standard C++ compiler as a valid program, so when the user clicks the "Upload

to I/O board" button in the Uno, a copy of the code is written to a temporary file with an extra

include header at the top and a very simple main ( ) function at the bottom, to make it a valid

C++ program.

The Aurduino Uno uses the GNU tool chain and AVR Lib to compile programs, and uses

avrdude to upload programs to the board. As the Aurduino platform uses Atmel microcontrollers

Atmels development environment, AVR Studio or the newer Atmel Studio, may also be used to

develop software for the Aurduino.


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5.1 PROGRAM FOR TEMPERATURE READING AND CONTROL

The program for the Temperature control using Aurduino is given as follows:

void setup( )

{

Serial.begin(9600);

pinMode(A1,INPUT);

pinMode(7,OUTPUT);

}

void loop( )

{

float x=analogRead(A1);

float v=x*5;

float v1=v/1023;

if(v1>3.7)

digitalWrite(7,HIGH);

else if(v1


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5.2 FLOW CHART

Figure 5.1 Flowchart for temperature sensing and control

start

Initialize input and output pins

A1=Input&&D7=Output

Read input atA1 =V1

If v1>3.7

D9=High D9=Low

YES

Stop


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RESULT

When the temperature in the chamber crosses the set temperature value the bulb is turned

off automatically and when the temperature falls below the set temperature value the bulb glows.

The temperature in the chamber is observed to be at a constant value.

Given below shows the state of the heating element (bulb) according to the readings

noted during the first 20 minutes of the experiment.

Output State of bulb

V1=2.08 ON

V1=2.09 ON

V1=3.12 ON

V1=3.23 ON

V1=3.34 ON

V1=3.45 ON

V1=3.50 ON

V1=3.53 ON

V1=3.54 ON

V1=3.64 ON

V1=3.68 ON

V1=3.71 OFF

V1=3.70 OFF

V1=3.68 ON

V1=3.71 OFF


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FUTURE SCOPE

We can incorporate the idea of Peltier effect to control the temperature of the chamber. They can

be used either for heating or for cooling (refrigeration), although in practice the main application

is cooling. It can also be used as a temperature controller that either heats or cools. But Peltier

elements are costly and shows poor power efficiency. Many researchers and companies are

trying to develop Peltier coolers that are both cheap and efficient. If such type of Peltier elements

are developed we can also introduce it in Infant incubators.

For Infants affected with Jaundice bile lights can be introduced in to the chamber. Apnea

monitoring can also be introduced for infants affected with Respiratory disorders.


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REFERENCES

[1] http://arduino.cc/en/Main/arduinoBoardUno

[2] http://www.me.umn.edu/courses/me2011/arduino/arduinoGuide.pdf

3 http://www.control.aau.dk/~jdn/edu/doc/arduino/litt/ArduinoTutorials.pdf

4 http://www.nunoalves.com/classes/spring_2012_cpe355/cpe355-02-a.pdf

5 http://www.fairchildsemi.com/ds/PN/PN2222A.pdf

[6] http://www.ia.omron.com/products/category/relays/general-purpose- relays/index.html

7 http://www.datasheetcatalog.com/datasheets_pdf/7/8/1/2/7812.shtml


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Appendix-B

2N2222

This device[9]

is for use as a medium power amplifier and switch requiring collector currents up

to 500mA.


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Typical Performance Characteristics:


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Appendix-C

Relay 12V dc[10]

, 7A


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Documents

CD 5 Main Documentation