BILLU FINAL REPORT 1

8/8/2019 BILLU FINAL REPORT 1

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Microcontroller Based Heart Rate Meter

INTRODUCTION

1.1 OVERVIEW

Heart rate can be measured either by the ECG waveform or by the blood flow into the

finger (pulse method). The pulse method is simple and convenient. When blood flows

during the systolic stroke of the heart into the body parts, the finger gets its blood via the

radial artery on the arm. The blood flow into the finger can be sensed photo electrically.

To count the heart beats, here we use a small light source on one side of the finger

(thumb) and observe the change in light intensity on the other side. The blood flow

causes variation in light intensity reaching the light dependent resistor (LDR), which

results in change in signal strength due to change in the resistance of the LDR.

1.2 LITERATURE SURVEY

We have chosen MICROCONTROLLER BASED HEART RATE METER using

AT89C2051 as our minor project. We have practically seen heart rate meter in places

like hospital and Doctors clinics. From here we got the idea to make this project. For

making this project we have studied the microcontroller from the book An introduction

to microcontroller by Mazidi and Mazidi and the Basic electronics book which

was available in our institute RAD innovation where we had done training in

Embedded systems and the rest of the material we have searched from internet. Before

making this project we searched the various components to be required are available in

the market or not. The most important portion or we can say Heart of this project is

SENSOR without which it seems to be incomplete and could not work. The various

books and links which we have followed in our report are given below.

Compiled by: Page 1 of66

Ashish (C07507), Balwinder Singh (C07508), Harshal (C07513)


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1) The 8051 Microcontroller and Embedded Systems,(2nd Edition)by Muhammad Ali

Mazidi, All the basic fundamentals of programming of microcontroller 8051 were

studied from this book.

2) http://www.play-hookey.com/digital/experiments/seven_seg_led.html:-One common

requirement for many different digital devices is a visual numeric display. Individual

LEDs can of course display the binary states of a set of latches or flip-flops.

However, we're far more used to thinking and dealing with decimal numbers.

Therefore we have used a 7-segment for display purposes.

3) www.national.com/pf/LM/LM358.html:- The LM358 series consists of two

independent, high gain, internally frequency compensated operational amplifiers

which were designed specifically to operate from a single power supply over a wide

range of voltages.

1.3 OBJECTIVE

We the students of Chandigarh College of Engineering & Technology (CCET) are

going to be graduates in Electronics & Electrical Communication Engineering &

Technology, we should have the theoretical as well as practical knowledge of various

electronic components being used in various electronic circuits. The main objective of

making this project is to grab practical knowledge of electronic components. We have

done our minor project (Microcontroller based heart rate meter) in which we used

various electronic components like diodes, ICs etc. We have also practiced soldering,

disordering, testing of components & fabrication of components on PCB.

Another Objective behind choosing the project is to understand the use of

microcontroller in various electronic circuits.




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1.4 ORGANISATION OF REPORT

This report has been written in manner in which the development of the project has been

made. Certain modifications have been made in order to make the understanding simpler.

This report has been divided into various chapters. Brief description of these chapters is

discussed below:

Chapter 1

It deals with the general introduction of the project. It gives as overview to the project by

covering the literature that had been surveyed to get all relevant information. This chapter

ends with the objective of this project which also covers some practical aspects of the

projects.

Chapter 2

Thischapter deals with the description of various section of the project. Which type of

components were used in order achieve the desired target. How PCB is printed and make

sure its tracks are good enough for the conductivity.

Chapter 3

This chapter explains how the circuit is printed on a copper clad PCB using different

techniques and software thus helping to avoid any sort of short circuit in projects as there

are a lot of wire in general purpose PCBs.

Chapter 4

This chapter explains the hardware model of the project. This gives you an idea how

project will look like after completion and how will it work. How reading are observed

on it.




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MODULAR DESCRIPTION

1. Soldering

2. Power supply

3. Control Unit

4. Display Section

5. Circuit Description

6. PCB Designing

7. Testing

Fig 2.1 Block diagram of Heart Rate Meter




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2.1 Soldering

Soldering is a process in which two or more metal items are joined together by melting

and flowing a filler metal into the joint, the filler metal having a relatively low melting

point. Soft soldering is characterized by the melting point of the filler metal, which is

below 400 C (800 F). The filler metal used in the process is called solder.

2.1.1 Applications

One of the most frequent application of soldering is assembling electronic components toprinted circuit boards (PCBs). Another common application is making permanent but

reversible connections between copper pipes in plumbing systems. Joints in sheet metal

objects such as food cans, roof flashing, rain gutters and automobile radiators have also

historically been soldered, and occasionally still are. Jewelry components are assembled

and repaired by soldering. Small mechanical parts are often soldered as well. Soldering is

also used to join lead came and copper foil in stained glass work. Soldering can also be

used to effect a semi-permanent patch for a leak in a container cooking vessel.

2.1.2 Solders

Soldering filler materials are available in many different alloys for differing applications.

In electronics assembly, the eutectic alloy of 63% tin and 37% lead (or 60/40, which is

almost identical in performance to the eutectic) has been the alloy of choice. Other alloys

are used for plumbing, mechanical assembly, and other applications. Lead-free solders

are suggested anywhere children may come into contact (since children are likely to place

things into their mouths), or for outdoor use where rain and other precipitation may wash

the lead into the groundwater.

Common solder alloys are mixtures of tin and lead, respectively:




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63/37: melts at 183 C (361.4 F) (eutectic: the only mixture that melts at a point,

instead of over a range)

60/40: melts between 183190 C (361374 F)

50/50: melts between 185215 C (365419 F)

2.1.3 Flux

In high-temperature metal joining processes (welding, brazing and soldering), the

primary purpose of flux is to prevent oxidation of the base and filler materials. Tin-lead

solder, for example, attaches very well to copper, but poorly to the various oxides of

copper, which form quickly at soldering temperatures. Flux is a substance which is nearly

inert at room temperature, but which becomes strongly reducing at elevated temperatures,

preventing the formation of metal oxides. Secondarily, flux acts as a wetting agent in the

soldering process, reducing the surface tension of the molten solder and causing it to

better wet out the parts to be joined.

Fluxes currently available include water-soluble fluxes and 'no-clean' fluxes which are

mild enough to not require removal at all. Performance of the flux needs to be carefully

evaluated; a very mild 'no-clean' flux might be perfectly acceptable for production

equipment, but not give adequate performance for a poorly-controlled hand-solderingoperation.

2.1.4 Basic soldering techniques

Methods

Soldering operations can be performed with hand tools, one joint at a time, or en masse

on a production line. Hand soldering is typically performed with a soldering iron,

soldering gun, or a torch, or occasionally a hot-air pencil. Sheet metal work was

traditionally done with "soldering coppers" directly heated by a flame, with sufficient

stored heat in the mass of the soldering copper to complete a joint; torches or electrically-




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heated soldering irons are more convenient. All soldered joints require the same elements

of cleaning of the metal parts to be joined, fitting up the joint, heating the parts, applying

flux, applying the filler, removing heat and holding the assembly still until the filler metal

has completely solidified. Depending on the nature of flux material used, cleaning of the

joints may be required after they have cooled.

"Hard soldering" or "silver soldering" (performed with high-temperature solder

containing up to 40% silver) is also often a form of brazing, since it involves filler

materials with melting points in the vicinity of, or in excess of, 450 C. Although the

term "silver soldering" is used much more often than "silver brazing", it may be

technically incorrect depending on the exact melting point of the filler in use. In silver

soldering ("hard soldering"), the goal is generally to give a beautiful, structurally sound

joint, especially in the field of jewelry. Thus, the temperatures involved, and the usual use

of a torch rather than an iron, would seem to indicate that the process should be referred

to as "brazing" rather than "soldering", but the endurance of the "soldering" apellation

serves to indicate the arbitrary nature of the distinction (and the level of confusion)

between the two processes.

Induction soldering is a process which is similar to brazing. The source of heat in

induction soldering is induction heating by high-frequency AC current. Generally copper

coils are used for the induction heating. This induces currents in the part being soldered.

The coils are usually made of copper or a copper base alloy. The copper rings can be

made to fit the part needed to be soldered for precision in the work piece. Induction

soldering is a process in which a filler metal (solder) is placed between the faying

surfaces of (to be joined) metals.

The filler metal in this process is melted at a fairly low temperature. Fluxes are a

common use in induction soldering. This is a process which is particularly suitable for

soldering continuously. The process is usually done with coils that wrap around a

cylinder/pipe that needs to be soldered. Some metals are easier to solder than others.




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adjustable or fixed temperature

power source (electric or gas)

portable or bench use

I do not recommend soldering guns, as these have no temperature control and can get too

hot. This can result in damage to circuit boards, melt cable insulation, and even damage

connectors.

Wattage

It is important to realise that higher wattage does not necessarily mean hotter soldering

iron. Higher wattage irons just have more power available to cope with bigger joints. A

low wattage iron may not keep its temperature on a big joint, as it can loose heat faster

than it can reheat itself. Therefore, smaller joints such as circuit boards require a lesser

wattage iron - around 15-30 watts will be fine. Audio connectors need something bigger -

I recommend 40 watts at least.

Temperature

There are a lot of cheap, low watt irons with no temperature control available. Most of

these are fine for basic soldering, but if you are going to be doing a lot you may want to

consider a variable temperature soldering iron. Some of these simply have a boost button

on the handle, which is useful with larger joints, others have a thermostatic control so you

can vary the heat of the tip.

Figure Solder Iron




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If you have a temperature controlled iron you should start at about 315-345C (600-

650F). You may want to increase this however - I prefer about 700-750F. Use a

temperature that will allow you to complete a joint in 1 to 3 seconds.

Power

Most soldering irons are mains powered - either 110/230v AC, or benchtop soldering

stations which transform down to low voltage DC. Also available are battery and gas

powered. These are great for the toolbox, but you'll want a plug in one for your bench.

Gas soldering irons loose their heat in windy outside conditions more easily that a good

high wattage mains powered iron.

Figure Power Rating

Portability

Most cheaper soldering irons will need to plug into the mains. This is fine a lot of the

time, but if there is no mains socket around, you will need another solution. Gas and

battery soldering irons are the answer here. They are totally portable and can be taken and

used almost anywhere. They may not be as efficient at heating as a good high wattage

iron, but they can get you out of a lot of hassle at times.




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Figure

If you have a bench setup, you should consider using a soldering station. These usually

have a soldering iron and desoldering iron with heatproof stands, variable heat, and a

place for a cleaning pad. A good solder station will be reliable, accurate with itstemperature, and with a range of tips handy it can perform any soldering task you attempt

with it.

Solder

The most commonly used type of solder is rosin core. The rosin is flux, which cleans as

you solder. The other type of solder is acid core and unless you are experienced atsoldering, you should stick to rosin core solder. Acid core solder can be tricky, and better

avoided for the beginner.

Figure

Rosin core solder comes in three main types - 50/50, 60/40 and 63/37. These numbers

represent the amount of tin and lead are present in the solder,as shown below:




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Solder Type % Tin % Lead Melting Temp (F)

50/50 50 50 425

60/40 60 40 371

63/37 63 37 361

Any general purpose rosin core solder will be fine.

Soldering Accessories

Soldering Iron Tips

Try to use the right size tip whenever you can. Smaller wires and circuit boards require

small fine tips, and mic cable onto an XLR would need a larger tip. You can get pointed

tips, or flat tipped ones (sometimes called 'spade tips'). If you have a solder station with a

desolderer, you will also want a range of desoldering tips and cleaners.

Figure

Soldering Iron Stands

These are handy to use if you are doing several or more joints. It is a heat resistant cradle

for your iron to sit in, so you don't have to lie it down on the bench while it is hot. It

really is essential if you are planning to do a lot of bench soldering as it is only a matter

of time before you burn something (probably your elbow resting on the hot tip) if you

don't use one.




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figure

Clamps

I strongly recommend clamps of some sort. Trying to hold your soldering iron, the solder,

and the wire is tricky enough, but when you have to hold the connector as well it is

almost impossible. The are however, adjustable clamps that can be manipulated to hold

both the connector and the wire in place so you still have two free hands to apply the heatand the solder. These are cheap items, and I know mine have paid for themselves many

times over.

Magnifying glass

If you are doing work on PCBs (printed circuit boards) you may need to get a magnifying

glass. This will help you see the tracks on the PCB, and unless you have exceptional

sight, small chip resistors are pretty difficult to solder on well without a magnifying glass.

Once again, they are not expensive, and some clamps come with one that can mount on

the clamp stand.




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figure

Solder Wick

Solder wick is a mesh the you lie on a joint and heat. When it heats up it also melts thesolder which is drawn out of the joint. It is usually used for cleaning up solder from

tracks on a circuit board, but you will need a solder sucker to clean out the holes in the

circuit board. Place the wick on the solder you want to remove then put your soldering

iron on top of the wick. The wick will heat up, then the solder will melt and flow away

from the joint and into wick.

figure

Solder Suckers

If you don't have a solder station with desolderer, and you work on PCB's, you are going

to need one of these before too long. They are spring loaded and suck the melted solder

out of the joint. They are a bit tricky to use, as you have to melt the solder with your iron,

then quickly position the solder sucker over the melted solder and release the spring to

suck up the solder. I find solder wick to be easier to use and more effective.

figure




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Fume Extractors

Solder fumes are poisonous. A fume extractor will suck the fumes (smoke) into itself and

filter it. An absolute must for your health if you are setting up a soldering bench.

figure

2.1.7Soldering

This step can often be the easiest when soldering audio cables. You simply need to place

your soldering iron onto the contact to melt the solder. When the solder in the contact

melts, slide the wire into the contact. Remove the iron and hold the wire still while the

solder solidifies again. You will see the solder 'set' as it goes hard.

figure

This should all take around 1-3 seconds.

A good solder joint will be smooth and shiny.

If the joint is dull and crinkly, the wire probably moved during soldering.

If you have taken too long it will have solder spikes.




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figure

If it does not go so well, you may find the insulation has melted, or there is too much

stripped wire showing. If this is the case, you should desolder the joint and start again.

2.1.8 Tips and Tricks

1. Melted solder flows towards heat.

2. Most beginning solder tend to use too much solder.

3. Don't move the joint until the solder has cooled.

4. Keep your iron tip clean.

5. Use the proper type of iron and tip size.

2.1.9 Troubleshooting

If either of the parts you are soldering is dirty or greasy, the solder won't take (or 'stick')

to it. Desolder the joint and clean the parts before trying again. Another reason the solder

won't take is that it may not be the right sort of metal. For example you cannot solder

aluminium with lead/tin solder. If the joint has been moved during soldering, it may look

grainy or dull. It may also look like this if the joint was not heated properly while

soldering. If the joint was overheated the solder will have formed a spike and there will

be burnt flux residue.




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2.1.10 Power supply

Fig 2.2 Block diagram of a power supply

Fig 2.3 Requirements of a power supply

Above is the circuit of a basic unregulated dc power supply. A bridge rectifier D1 to D4

rectifies the ac from the transformer secondary, which may also be a block rectifier such as




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WO4 or even four individual diodes such as 1N4004 types. The principal advantage of a

bridge rectifier is you do not need a centre tap on the secondary of the transformer. A

further but significant advantage is that the ripple frequency at the output is twice the line

frequency (i.e. 50 Hz or 60 Hz) and makes filtering somewhat easier.

Resistors

Example: Circuit symbol:

Resistors restrict the flow of electric current, for example a resistor is placed in series

with a light-emitting diode (LED) to limit the current passing through the LED.

Resistors may be connected either way round. They are not damaged by heat when

soldering.

Resistor values - the resistor colour code

Resistance is measured in ohms, the symbol for ohm is an omega .

1 is quite small so resistor values are often given in k and M .

1 k = 1000 1 M = 1000000 .

Resistor values are normally shown using coloured bands.

Each colour represents a number as shown in the table.



The Resistor

Colour Code

Colour Number

Black 0

Brown 1

Red 2

Orange 3

Yellow 4

Green 5

Blue 6

Violet 7

Grey 8

White 9


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Most resistors have 4 bands:

The first band gives the first digit.

The second band gives the second digit.

The third band indicates the number of zeros. The fourth band is used to shows the tolerance (precision) of the resistor, this

may be ignored for almost all circuits but further details are given below.

This resistor has red (2), violet (7), yellow (4 zeros) and gold bands.

So its value is 270000 = 270 k . On circuit diagrams the is usually omitted and the

value is written 270K.


http://www.kpsec.freeuk.com/components/resist.htm#tolerancehttp://www.kpsec.freeuk.com/components/resist.htm#tolerance


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Capacitors

The capacitor's function is to store electricity, or electrical energy.

The capacitor also functions as a filter, passing alternating current (AC), and blocking direct

current (DC).

This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an

insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each electrode.

While the capacitor is charging up, current flows. The current will stop flowing when the

capacitor has fully charged.

figure

When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10

microfarad (F) electrolytic capacitor, a current will flow, but only for a moment. You can




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confirm that the meter's needle moves off of zero, but returns to zero right away.

When you connect the meter's probes to the capacitor in reverse, you will note that current

once again flows for a moment. Once again, when the capacitor has fully charged, the

current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A

"DC cut" filter.)

However, in the case of alternating current, the current will be allowed to pass. Alternating

current is similar to repeatedly switching the test meter's probes back and forth on the

capacitor. Current flows every time the probes are switched. The value of a capacitor (the

capacitance), is designated in units called the Farad(F).The capacitance of a capacitor is

generally very small, so units such as the microfarad (10-6F), nanofarad (10-9F), and

picofarad (10-12F) are used.

Recently, an new capacitor with very high capacitance has been developed. The Electric

Double Layer capacitor has capacitance designated in Farad units. These are known as

"Super Capacitors."

Sometimes, a three-digit code is used to indicate the value of a capacitor. There are two

ways in which the capacitance can be written. One uses letters and numbers, the other uses

only numbers. In either case, there are only three characters used. [10n] and [103] denote

the same value of capacitance. The method used differs depending on the capacitor supplier.

In the case that the value is displayed with the three-digit code, the 1st and 2nd digits from

the left show the 1st figure and the 2nd figure, and the 3rd digit is a multiplier which

determines how many zeros are to be added to the capacitance. Picofarad ( pF ) units are

written this way. For example, when the code is [103], it indicates 10 x 10 3, or 10,000pF =

10 nanofarad( nF ) = 0.01 microfarad( F ).

Diodes




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Example:

figure

Circuit symbol:

figure

Diodes allow electricity to flow in only one direction. The arrow of the circuit symbol

shows the direction in which the current can flow. Diodes are the electrical version of a

valve and early diodes were actually called valves.

figure

Light Emitting Diodes (LEDs)




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Example:

Circuit symbol:

LEDs emit light when an electric current passes through them.

figure

LEDs must be connected the correct way round, the diagram may be labelled a or+ for

anode and kor- for cathode (yes, it really is k, not c, for cathode!). The cathode is the

short lead and there may be a slight flat on the body of round LEDs. If you can see inside

the LED the cathode is the larger electrode (but this is not an official identification

method). LEDs can be damaged by heat when soldering, but the risk is small unless you

are very slow. No special precautions are needed for soldering most LEDs.

2.1.2 ULN 2003:

DESCRIPTION:

The ULN2003 is a high voltage, high current darlington array containing seven open

collector darlington pairs with common emitters. Each channel rated at 500mA and can

withstand peak currents of 600mA. Suppression diodes are included for inductive load

driving and the inputs are pinned opposite the outputs to simplify board layout.




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The versions interface to ULN2003A 5V is TTL, CMOS. These versatile devices are

useful for driving a wide range of loads including solenoids, relays DC motors; LED

displays filament lamps, thermal print heads and high power buffers. The ULN2003 is

supplied in 16 pin plastic DIP packages with a copper lead frame to reduce thermal

resistance.

Fig 2.4 ULN2003

Features:-

Output Voltage up to 50 V

Input Voltage up to 30 V

Continuous Collector Current - 500 mA

Continuous Base Current - 25 mA

Operating Ambient Temperature Range - 20 to 85 C

Storage Temperature Range - 55 to 150 C

Junction Temperature 150 C

WORKING:

Voltage regulator limits the voltage that passes through it. Each regulator has a




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voltage rating; For example, the 7805 IC (these regulators are often considered to be ICs)

is a 5-volt voltage regulator. What that means is that no matter how many volts you put

into it, it will output only 5 volts. This means that you can connect a 9-volt battery, a

12-volt power supply, or virtually anything else that's over 5 volts, and have the 7805

give you a nice supply of 5 volts out. There are also 7812 (12-volt) and 7815 (15-volt)

three pin regulators in common use.

The pin-out for a three pin voltage regulator is as follows:

1. Voltage-in

2. Ground

3. Voltage out

For example, with a 9-volt battery, you'd connect the positive end to pin 1 and the

negative (or ground) end to pin 2. A 7805 would then give you +5 volts on pin 3.Voltage

regulators are simple and useful. There are only two important drawbacks to them: First,

the input voltage must be higher than the output voltage. For example, you cannot give a

7805 only 2 or 3 volts and expect it to give you 5 volts in return. Generally, the input

voltage must be at least 2 volts higher than the desired output voltage, so a 7805 would

require about 7 volts to work properly. The other problem: The excess voltage isdissipated as heat. At low voltages (such as using a 9-volt battery with a 7805), this is not

a problem. At higher voltages, however, it becomes a very real problem and you must

have some way of controlling the temperature so you don't melt your regulator. This is

why most voltage regulators have a metal plate with a hole in it; That plate is intended for

attaching a heat sink to-Do not confuse three-pin voltage regulators with a device known

as a TRIAC (short for triode AC switch). It is easy to associate them with each other,

since they look similar (both have three pins) and they both regulate power. However, the

78XX types of regulators are used for regulating DC current, while TRIACs are used for

AC current.




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2.2 Control Unit:

Microcontroller is used to control our hardware using programs which we make

according to our requirement. In our project the devices connected with the

Microcontroller are:a) Display unit

b) Heart Rate monitoring unit

c) Switches.

Output of IC is given to microcontroller and as per our requirement controller controls

the hardware according to heart rate and side by side it displays the heart beat in decimal

number system on Common anode 7-seg display.

2.3 Display Section

Common anode 7-segment display is used for display purpose. These are finding

widespread use in various applications. A seven-segment display, or seven-segment

indicator, is a form of electronic display device for displaying decimal numerals that is

an alternative to the more complex dot-matrix displays. Seven-segment displays are

widely used in digital clocks, electronic meters, and other electronic devices for

displaying numerical information. They are preferred because of ease of programming for

characters and numbers. We have used LT542 3 common anode 7-seg display.

2.4 Circuit Description




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Fig.2.5 Circuit Diagram

The setup uses a 6V electric bulb for light illumination of flesh on the thumb

behind the nail and the LDR as detector of change in the light intensity due to the flow of

blood. The photo-current is converted into voltage and amplified by operational amplifier

IC LM358 (IC1). The detected signal is given to the non-inverting input (pin 3) and its

output is fed to another non-inverting input (pin 5) for squaring and amplification. Output

pin 7 provides detected heartbeats to pin 12 of the microcontroller. Preset VR1 is used for

sensitivity and preset VR2 for trigger level settings.

Microcontroller IC AT89C2051 (IC2) is at the heart of the circuit. It is a 20-pin,8-bit

microcontroller with 2 kB of Flash programmable and erasable read-only memory

FEROM), 128 bytes of RAM, 15 input/output (l/O) lines, two 16-bit timer/counters, a

five-vector two-level interrupt architecture, a full duplex serial port, a precision analogue

comparator, on-chip oscillator and clock circuitry.

Port-1 pins P1.7 through P1.2, and port-3 pin P3.7 are connected to input pins 1

through 7 of IC ULN2003 (IC3), respectively. These pins are pulled-up with 10-kilo-ohm

resistor network RNW1. They drive all the segments of the 7-segment display with the

help of inverting buffer IC3.

The displays are selected through port pins P3.0, P3.1 and P3.2 of the

microcontroller (IC2). Port pins P3.0 down through P3.2 are connected to the base of




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transistors T3 through T1, respectively. Pin 6 of IC2 goes low to drive transistor T1 into

saturation and provide supply to the common-anode pin (either pin 3 or pin 8) of DIS1.

Similarly, transistors T2 and T3 drive common-anode pin 3 or 8 of 7-segment

displays DIS2 and DIS3, respectively. Only three 7-segment displays are used. IC2

provides segment-data and display-enable signals simultaneously in time-division-

multiplexed mode for displaying a particular number on the 7-segment display unit.

Segment- data and display-enable pulses for the display are refreshed every 5 ms. Thus

the display appears to be continuous/ even though it lights up one by one.

Switch S2 is used to manually reset the microcontroller, while the power on reset

signal for the microcontroller is derived from the combination of capacitor C4 and

resistor R8. An 11.0592MH2 crystal is used to generate the basic clock frequency for the

microcontroller. The circuit is powered by a 6V battery. Port pin P3.6 of the

microcontroller is internally available for software checking. This pin is actually the

output of the internal analogue comparator, which is available internally for comparing

the two analogue levels at pins 12 and 13. As pins 12 and 13 of IC2 can work as an

analogue comparator, these are used for sensing the rise and fall of the pulse waveform

and thereby evaluate the time between two peaks and hence the beat rate.

The output of the pulse pick-up preamplifier is fed to pin 12 of the microcontroller. Pin

13 of the microcontroller is connected to the preset for reference-level setting of the

comparator.

Thus voltages at pins 12 and 13 are always compared. The signal rise and the fall

at pin 12 are sensed by the program. The internal timer of the microcontroller is used to

find the time taken for one wavelength. This time is converted into the heart beat rate in

beats per minute by a pre-calculated look-up table. The program notes the time between

the high to low and low-to-high transitions of the wave. This time in microseconds is




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converted in steps of 4 ms for comparison with the values already stored in the look-up

table.

This number is used to find (from the look-up table) the heart rate in beats per

minute. The number so obtained is converted into a 3-digit number in binary-coded

decimal (BCD) form. The same is output to the 7-segment LED displays in a multiplexed

manner. The display shows the rate for a while and proceeds to another measurement.

Thus beat rates obtained from time to time are visible on the Display.

2.5 Programming of microcontroller

2.5.1 Beginning

a. Open Keil from the Start menu

b. The Figure below shows the basic names of the windows referred in this document




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2.5.2 Starting a new Assembler Project

a. Select New Project from the Project Menu




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b. Name the project Toggle.a51

c. Click on the Save Button.

d. The device window will be displayed.

e. Select the part you will be using to test with. For now we will use the Dallas

Semiconductor part DS89C420.




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f. Double Click on the Dallas Semiconductor.

g. Scroll down and select the DS89C420 Part

h. Click OK




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2.5.3 Creating Source File




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a. Click File Menu and select New.

b. A new window will open up in the Keil IDE.




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c. Copy the example to the Right into the new window. This file will toggle Ports 1

and 2 with a delay.

d. Click on File menu and select Save As




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e. Name the file Toggle.a51

f. Click the Save Button

2.5.4 Adding File to the Project

a. Expand Target 1 in the Tree Menu




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b. Click on Project and select Targets, Groups, Files

c. Click on Groups/Add Files tab

d. Under Available Groups select Source Group 1

e. Click Add Files to Group button




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f. Change file type to Asm Source file(*.a*;*.src)

g. Click on toggle.a51h. Click Add button

i. Click Close Button

j. Click

button

return to Target,

Groups, Files

dialog box




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k. Expand the Source Group 1 in the Tree menu to ensure that the file was added to the

project




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2.5.5 Creating HEX for the Part

a. Click on Target 1 in Tree menu

b. Click on Project Menu and select Options for Target 1




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c. Select Target Tab

d. Change Xtal (Mhz) from 50.0 to 11.0592




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e. Select Output Tab

f. Click on Create Hex File check box

g. Click OK Button




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h. Click on Project Menu and select Rebuild all Target Files

i. In the Build Window it should report 0 Errors (s), 0 Warnings

j. You are now ready to Program your Part




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PCB DESIGNING

Printed Circuit Board Etching:-

Etching is where the excess copper is removed to leave the individual tracks or traces as

they are sometimes called. Buckets, bubble tanks, and spray machines lots of different

ways to etch, but most firms currently use high pressure conveyerised spray equipment.

Spray etching is fast, ammoniacal etching solutions when sprayed can etch 55 microns of

copper a minute. Less than 40 seconds to etch a standard 1 oz, 35 micron circuit board.

Many different chemical solutions can be used to etch circuit boards. Ranging from slow

controlled speed etches used for surface preparation to the faster etches used for etching

the tracks. Some are best used in horizontal spray process equipment while others are

best used in tanks. Etchents for PTH work have to be selective and be non aggressive to

tin / tin lead plating, which is used as the etch resist. Copper etching is normally

exothermic, where high speed etching is carried out solution cooling is normally required.

This is normally done by placing titanium water cooling coils into the etchent. Almost all

etching solutions liberate toxic corrosive fumes, extraction is highly recommended. All

etchents are corrosive and toxic, mainly due to the high metal content. P.P.E. Personal

Protection Equipment must always be used, spent solutions should always be disposed of

properly and not down local drains, where they pollute local sewage works and rivers.

Ferric Chloride.

An old favorite, also very good at staining fingers, clothing, etc brown. Etch rate can be

very high but is dependant on solution movement over the surface of the board and

temperature. At 70C using Spray etching 1oz copper is removed in a little under a

minute, normal etching temperature is more likely to be 45C. When etching circuits if up

to 5% of HCL is added it, increases etch rate, helps to stop staining, and reduces the risk




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of the solution sludging. Ferric especially with extra HCL makes a very good stainless

steel etchent.

When Ferric crystals are mixed with water some free HCL produced through hydrolysis.

FeCl3 + 3H2O > Fe(OH)3 + 3HCL

The basic etching reaction takes place in 3 stages. First the ferric ion oxidizes copper to

cuprous chloride, which is then further oxidized to cupric chloride.

FeCl3 + Cu > FeCl2 + CuCl

FeCl3 + CuCl > FeCl2 + CuCl2

As the cupric chloride builds up at further reaction takes place,

CuCl2 + Cu > 2CuCl

The etch rate quickly falls off after about 17oz/gallon (100g/l of copper has been etched.

For a typical solution containing 5.3lb/gallon (530g/l) of ferric chloride.

PCB Etching

Since the introduction of laser printers making your own PCBs (Printed Circuit Boards)

has become fairly easy. The method described here assumes you want to make a PCB

from an electronics magazine PCB layout - so you can copy it with a copier - or you are

able to print your own PCB layouts from a PCB design package or have them available in

electronic format and you can print them with a laser printer.

I am using the described method below successfully since 1996. I was forced to find an

etching method to be used at home after the company I worked for dumped their




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prototype PCB production tools. A short version of the `greasy' etching method has been

published August 2000 in the newsletter `Vijgeblaadje' from the Dutch FIG (HCC Forth

gebruikersgroep).

PCB Layout

PCB Preparation

PCB UV Exposure

PCB Development

PCB Etching

Trouble shooting

More Examples

PCB Layout

The PCB layout is a mirrored positive one - black on white. Mirrored as viewed from the

silkscreen top (component) side. The PCB layout is printed 1:1 on paper by means of a

laser printer or copier machine. The laser printer or copier toner will not run out when it

gets wet or oily. The ink of an inkjet paper print does run out and inkjet printers are

therefore useless with the described method.

I have used several types of HP laser printers (LaserJet Series II, 5L, 4000 and 1100).

These printers work fine. It might be possible that the toner texture on the layout prints

from your used laser printer is not dense enough and passes too much light. However,

results might be improved by setting the toner density to maximum. Generally printer

driver properties allow to set the toner density.

PCB Preparation

The PCB layout paper is drenched with sunflower-seed oil. Sunflower-seed oil is

common available from your local grocery or wall market. Superfluous oil should be


http://www.forth.hccnet.nl/http://sfprime.net/pcb-etching/index.htm#layout%23layouthttp://sfprime.net/pcb-etching/index.htm#preparation%23preparationhttp://sfprime.net/pcb-etching/index.htm#exposure%23exposurehttp://sfprime.net/pcb-etching/index.htm#development%23developmenthttp://sfprime.net/pcb-etching/index.htm#etching%23etchinghttp://sfprime.net/pcb-etching/index.htm#trouble%23troublehttp://sfprime.net/pcb-etching/index.htm#more%23morehttp://www.forth.hccnet.nl/http://sfprime.net/pcb-etching/index.htm#layout%23layouthttp://sfprime.net/pcb-etching/index.htm#preparation%23preparationhttp://sfprime.net/pcb-etching/index.htm#exposure%23exposurehttp://sfprime.net/pcb-etching/index.htm#development%23developmenthttp://sfprime.net/pcb-etching/index.htm#etching%23etchinghttp://sfprime.net/pcb-etching/index.htm#trouble%23troublehttp://sfprime.net/pcb-etching/index.htm#more%23more


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removed carefully with tissue paper. The sunflower-seed oil is used to make the white

part of the layout paper transparent for light.

If you prefer to use the PCB layout more than once let the drenched PCB layout paper

dry at least 48 hours. The layout paper should be carefully dried on forehand as much as

possible with tissue paper. Sunflower-seed oil is a `drying' oil. Exposed to the air over a

number of hours, the layout paper becomes rigid again. A kind of polymerization takes

place. You will get a lot less or no greasy fingers anymore afterwards.

Other mineral or vegetable oils might work as well to obtain light transparency.

However, they might not be `drying' oils. When I started experimenting, sunflower-seed

oil was the first oil I used and it worked fine. So I didn't try any other oils. Using water

does not work. The layout paper crumples up a bit.

Drench layout with sunflower-seed oil

Layout fully drenched




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Greasy layout

PCB UV Exposure




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The protective plastic layer is removed - peeled back - from the photosensitive PCB. The

toner side of the greased layout is placed on the copper of the PCB. Captured air-bubbles

are gently pressed away from underneath the layout. The PCB with the layout is now

covered with an appropriate sized windowpane and placed on a piece of plain polished

tile or marble. The tile or marble absorbs the heat coming from the UV bulb, which is

significant. Three to four minutes 300W bulb UV exposure from a distance of 30-40 cm

will do the photo process. Take care when finished and removing the PCB, it gets hot!

Home-built UV exposure box with 300W UV bulb, polished tile and

window pane




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PCB with partly peeled back protective plastic layer and `dried' la




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Place layout with toner side on copper of the PCB

Cover PCB and layout with window-pane




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Exposure

PCB Development

The PCB is developed with a 1% solution of sodium hydroxide NaOH. You can make

this solvent by adding 10 gram ofsodium hydroxide pellets to 1 liter of water and mix it

until everything is dissolved. Use a brush to speed up the developing and clean the PCB

during this process if the PCB is still greasy due to the applied sunflower-seed oil. The

developing process takes about 1 minute. It is sometimes difficult to guess when the

developing is finished. The traces should become clear and the exposed photosensitive

layer has dissolved (during the brushing you see darker `cloud' coming off the PCB

surface).




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Gently brush the PCB Almost developed, some traces are not

clear yet

PCB Etching

The developed PCB is etched with a 220 g/l solution of ammonium peroxydisulfate

(NH4)2S2O8 a.k.a. ammonium persulfate, 220 gram added to 1 liter of water and mix it

until everything is dissolved. Theoretically it should be possible to etch slightly more

than 60 grams of copper with 1 liter etching solution. Assume an 50% efficiency, about

30 grams of copper. With a thickness of 35 m copper on your PCB this covers a copper

area of about 1000 cm2. Unfortunately the efficiency of the etching solution degrades,

dissolved ammonium peroxydisulfate decomposes slowly. You better make just enough

etching solution you need to etch. For an etching tray of about 20 x 25 cm a minimum

practical amount is 200-250 ml solution. So you dissolve about 44 grams ammoniumperoxydisulfate into 200 ml or 55 grams into 250 ml water.




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Etching at ambient temperature might take over an hour, it is better to heat up the etching

solvent to about 35-45 degrees Celcius. The etching solution heating up could be done in

a magnetron, this takes about 40 to 60 seconds in a 850W magnetron depending on the

initial temperature of the etching solution (hint: first try this with just water to determine

the timer setting of the magnetron). The etching - rocking the etching tray - takes about

15-30 minutes at this temperature. If you have a heated, air-bubble circulated etching

fluid tank available, this is probably the fastest way to etch. At higher temperatures the

etching performance decreases. The etching process is an exothermic reaction, it

generates heat. Take care, cool your etching tray when necessary! You should minimize

the amount of copper to etch by creating copper area in your PCB layout as much as

possible. When starting the etching process and little to etch it is difficult to keep the

etching solution at 35-45 degrees Celcius. It helps to fill for example the kitchen sink

with warm water and rock the etching tray in the filled kitchen sink.

When the ammonium peroxydisulfate is dissolved it is a clear liquid. After an etching

procedure it gradually becomes blue and more deeper blue - the chemical reaction creates

dissolved copper sulfate CuSO4. Compared to other etching chemicals like hydrated iron

(III) chloride FeCl3.6H2O a.k.a. ferric chloride or the combination ofhydrochloric acid

HCL and hydrogen peroxide H2O2, using ammonium peroxydisulfate is a clean and safe

method. Did you ever spilled dissolved iron chloride on your clothes or your assumed

stainless steel kitchen sink? Do you really want to keep concentrated hydrochloric acid

and hydrogen peroxide at home? So, without doubt ammonium peroxydisulfate is the best

choice for etching at home. However, copper sulfate is a poisonous substance and should

be treated as chemical waste.




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Rock the etching tray The epoxy of the PCB becomes visible

Almost finishedThe etching solution colors slighty blue




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Finished

Trouble shooting

The above mentioned exposure timing should be determined experimentally. But even

when the exposure timing is correct PCB etching failures could happen because of low

quality or too old photosensitive PCB, the photosensitive layer has aged despite the

protective plastic layer. Other possible causes are too high concentration of development

solution causing the photosensitive part not exposed to light to be dissolved by the

sodium hydroxide solution as well. When developing too short not all of the copper of the

PCB will be etched. Developing might take some experimenting to get used to it and

know what to expect. Furthermore set the toner density of your laser printer driver always

to maximum.

More examples




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Exposure

Development




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Etching Finished




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HARDWARE IMPLEMENTATION AND TESTING

4.1 Construction and testing

An actual-size, single-side PCB for the microcontroller-based temperature meter and its

component layout is shown in Fig. 2.6. Wire the circuit on the PCB. Use bases for ICs

AT8951. Program the AT89S51 with suitable programmer and put into the IC base after

soldering all the components and checking +5V at each Vcc point of the circuit. Also

check continuity between respective connections using a multimeter. An actual- size,

single-side PCB for the microcontroller based heart rate meter and component layout is

shown in shown below:

Fig.2.6 Component layout for the PCB




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The arrangement for heart beat rate detection is shown in Fig. 2. Purchase a plastic T

tube is used to fit LEDs and the LDR sensor. The tube should be about 5cm long and

have a diameter of 1.5 cm. House the electric bulb into the left tube and the LDR (sol-

dered on a small PCB) into the right tube. Fit shields on both sides of the tube to maintain

darkness for better performance. Connect the 6V battery supply to the bulb and the LDR

to the circuit board via a shielded cable.

Fig 2.7: T Tube with finger inserted

For heart beat detection, which can be seen on a cathode ray oscilloscope (CRO), insert

your thumb with the nail facing the LDR inside the T-tube. Shaking the thumb will

change the level of signal from the previous value, and it will keep oscillating. Therefore

you have to hold the thumb firmly between the light bulb and the LDR while the

measurement is being made.

Hold the thumb steady and observe the heart beat rate on the display. The rate may vary

and may not be exactly steady. For instance, normally, the rate can vary between 60 and

100.

Since this is a beat-to-beat measurement and not an average over a time period of one

minute, variation is expected. However, when the reading shows high value at times, say,




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140, it may be due to unusual mains hum picked up by the transducer. To suppress it,

place a separate capacitor of 100 F across the 5V supply.

This is how the project will look like after completion and reading are observed on it:




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CONCLUSION

The minor project which is used to test the technical skills of the student is the only way

to get the technical knowledge. While working on this project we are in a position to

conclude some of the points. The project has been rigorously tested and is found to work

under all practically possible situations.

Our project Microcontroller Based Heart Rate Meter is just a kind of practice work

and although we gave our hundred percent but still many more advancements can be

realized in future. Some of which are:

1. The results of the project can be displayed on CRO.

2. The heart beat can be listened using headphones.

3. This can be implemented on a large scale with the running cost turing out to be

very less.

This project has made us familiar with actual situations being faced in the projects. We

know that it was difficult task to establish at various points but we managed each and

every thing collectively. Now we are familiar with microcontroller programming, and we

have worked on many components that have been used in this project which otherwise

are difficult to be studied from the text books.

Troubleshooting which is an inherent part of any engineering project has widened our

thinking capacity. Main problem that we found was in software development. Although

we also faced problem in hardware, when some of components like LDR sensor using

finger etc were not working, and when we were not able to implement the correct




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algorithm for the working of the project but guidance of many faculty members, our

friends and parents encouragement made this whole experience extremely wonderful.

REFERENCES

[1] Muhammad Ali Mazidi, Janice GillispieMazidi, Rolin D. McKinlay , The 8051

Microcontroller & Embedded Systems, Pearson Education Inc. 2nd Edition, 2008.

[2] The 8051 Microcontroller by Kenneth Ayala

[3] www.atmel.com/dyn/resources/prod_documents/doc2487.pdf

[4] http://pdf1.alldatasheet.com/datasheet-pdf/view/77085/MITEL/MT8870.html

[5] http://www.datasheetcatalog.org/datasheets/105/366825_DS.pdf

[6] http://www.futurlec.com

[7] Yashwant Kanetkar,Let Us C++. 5

th

Edition


http://www.datasheetcatalog.org/datasheets/105/366825_DS.pdfhttp://www.futurlec.com/http://www.datasheetcatalog.org/datasheets/105/366825_DS.pdfhttp://www.futurlec.com/


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APPENDIX A

List of components

S.No. Code Name Value

1 R1,R4

R2,R3,R5-R8Resistor n/w

VR1-VR2

Resistors 330 ohms

10k10k

10k

2 C4,C5

C6

C2

C3C1

Capacitors 22Pf150pF

0.1F

10F2200F

3 IC1

IC2

IC3IC4

D1-D4

LED1,LED2

Microcontroller

OP-AMP

Regulator

Diode

LED

AT89S51

LM358

ULN2003LM7805

1N4007




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4 X1

Xtal

Transformer

Crystal

7-Segment

230V,500mA

11.0592MHz




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APPENDIX B :

DATASHEETS

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