CHAPTER ONE
INTRODUCTION
1.1
BACKGROUND OF THE STUDY
Photo entry system is designed to detect intrusion, unauthorized entry into a building or other
area. This system is used in residential, commercial, industrial, and military properties for
protection against burglary or property damage, as well as personal protection against
intruders, Prisons also use security systems for control of inmates. Some entry security
systems serve a single purpose of burglary protection; while others are combined with closedcircuit television surveillance (CCTV) systems to automatically record the activities of
intruders.
1.2
STATEMENT OF THE PROBLEM
Security challenge is one of the many problems we face in this country, this ranges from one
degree to another. There are situations whereby a room is made restricted and place under
surveillance. People may want to gain entrance into such a room for thief of any valuables left
in the room.
1.3
PURPOSE OF THE STUDY
The aim of this design is to build a photosensitive device that can be used to monitor both the
entry and exit of a door as to alert security personnel about a breach against a restricted door
that has been violated.
1.4
SIGNIFICANCE OF THE STUDY
The project design can serve as a security check against an intruder who wants to gain entry or
exit a door under monitor. It can be used to keep track of how many persons made an entry or
exit of a particular door in a day, this can be achieve coupled with other electronic devices
incorporated, but this particular project work only seek to notify that an entry or exit has just
1
been made through a door.
1.7 LIMITATION OF THE STUDY
Due to the economic situations of the country some core components could not be bought. The
absent of any well-equipped scientific laboratory slowed down the construction process.
1.8 DEFINITION OF TERMS
Photodiode: photodiode is a PN junction device.
Entry: This is a pass or an access.
Exit: This is an act of walking out, leaving a place, going away.
2
CHAPTER TWO
LITERATURE REVIEW
2.1 BACKGROUND OF THE PROJECT
The principle behind photo entry detector system is the transmission and receiving of infrared
light. An element known as a light emitting diode (LED) transmits active infrared light,
which is reflected on the other side of the door and received by an optical receiver known as a
photo diode (PD). As long as there is no movement or object in the path of the light beam, the
light pattern is static and the sensor remains in stand-by. When a person or object crosses the
beam, the reflection of the light is distorted. Aactive infrared sensors are excellent as a
safeguard at the door entry/exit because of their ability to continue recognizing changes that
occur in the detection area. As long as there is a person or object in the detection area, the
sensor remains active, automating the alarm to go on sounding. There is no theoretical limit
to the maximum time that can be set for a sensor, though this does depend on the type of
sensor. Infrared radiation was first discovered by the astronomer William Herschel. He
conducted an experiment in which he used a prism to refract light from the sun. Herschel was
able to detect the presence of infrared radiation beyond the red part of the visible spectrum
using a thermometer to measure an increase in temperature. In 1800 Herschel published his
findings to the Royal Society of London. John Bardeen, William Shockley and Walter
Brattain at Bell Labs, 1948. Later between November 17, 1947 to December 23, 1947, John
Bardeen and Walter Brattain at AT&T's Bell Labs in the United States performed experiments
and observed that when two gold point contacts were applied to a crystal of germanium, a
signal was produced with the output power greater than the input. Solid State Physics Group
leader William Shockley saw the potential in this, and over the next few months worked to
greatly expand the knowledge of semiconductors. The term transistor was devised by John R.
3
Pierce as a contraction of the term trans-resistance. According to Lillian Hoddeson and Vicki
Daitch, authors of a biography of John Bardeen, Shockley had proposed that Bell Labs' first
patent for a transistor should be based on the field-effect and that he be named as the
inventor. Instead, what Bardeen, Brattain, and Shockley invented in 1947 was the first pointcontact transistor. In acknowledgement of this accomplishment, Shockley, Bardeen, and
Brattain were jointly awarded the 1956 Nobel Prize in Physics "for their researches on
semiconductors and their discovery of the transistor effect."
LED founds use in many application, it happens to fall within the family of the p-n junction
device. The conducting surface of the p-type material is made smaller to permit the emergency
of the maximum number of photons of light energy when the device is forward biased, this is
one of the references to their wavelength rather than their frequency. The light intensity of an
LED will increase with forward current until a point of saturation is reached where any further
increase in current will not effectively increase the level of illumination. It is necessary to have
some idea of the voltage and current level before using it in a design work.
2.2
CIRCUIT COMPONENTS
2.2.1 PHOTODIODE: A photodiode is a PN junction or PIN structure. When a photon of
sufficient energy strikes the diode, it excites an electron, thereby creating a mobile electron and
a positively charged electron hole. If the absorption occurs in the junction's depletion region,
or one diffusion length away from it, these carriers are swept from the junction by the built-in
field of the depletion region. Thus holes move toward the anode, and electrons toward the
cathode, and a photo current is produced.
2.2.2 PHOTOVOLTAIC MODE: When used in zero bias or photovoltaic mode, the flow
of photocurrent out of the device is restricted and a voltage builds up. The diode becomes
forward biased and "dark current" begins to flow across the junction in the direction opposite
4
to the photocurrent. This mode is responsible for the photovoltaic effect, which is the basis for
solar cells in fact, a solar cell is just an array of large area photodiodes.
2.2.3 PHOTOCONDUCTIVE MODE: In this mode the diode is often (but not always)
reverse biased. This increases the width of the depletion layer, which decreases the junction's
capacitance resulting in faster response times. The reverse bias induces only a small amount of
current (known as saturation or back current) along its direction while the photocurrent remains
virtually the same.
The photocurrent is linearly proportional to the luminance.
Avalanche photodiodes have a similar structure to regular photodiodes, but they are operated
with much higher reverse bias. This allows each photo generated carrier to be multiplied by
avalanche breakdown, resulting in internal gain within the photodiode, which increases the
effective responsively of the device.
Phototransistors also consist of a photodiode with internal gain. A phototransistor is in essence
nothing more than a bipolar transistor that is encased in a transparent case so that light can
reach the base collector junction. The electrons that are generated by photons in the basecollector junction are injected into the base, and this photodiode current is amplified by the
transistor's current gain β (or hfe). Note that while phototransistors have a higher responsively
for light they are not able to detect low levels of light any better than photodiodes.
Phototransistors also have slower response times. The material used to make a photodiode is
critical to defining its properties, because only photons with sufficient energy to excite
electrons across the material's band-gap will produce significant photocurrents.
Materials commonly used to produce photodiodes include: Silicon 190–1100 nm,
Germanium 400–1700 nm, Indium gallium arsenide 800–2600 nm, and Lead sulfide <10003500 nm. Because of their greater band-gap, silicon-based photodiodes generate less noise than
germanium-based photodiodes, but germanium photodiodes must be used for wavelengths
5
longer than approximately 1 Km. Since transistors and ICs are made of semiconductors, and
contain P-N junctions, almost every active component is potentially a photodiode. Many
components, especially those sensitive to small currents, will not work correctly if illuminated,
due to the induced photocurrents. In most components this is not desired, so they are placed in
an opaque housing. Since housings are not completely opaque to X-rays or other high energy
radiation, these can still cause many ICs to malfunction due to induced photo-currents.
2.3
APPLICATIONS OF PHOTODIODE
P-N photodiodes are used in similar applications to other photo-detectors, such as
photoconductors, charge-coupled devices, and photomultiplier tubes. Photodiodes are used in
consumer electronics devices such as compact disc players, smoke detectors, and the receivers
for remote controls in VCRs and televisions. In other consumer items such as camera light
meters, clock radios (the ones that dim the display when it's dark) and street lights,
photoconductors are often used rather than photodiodes, although in principle either could be
used.
Photodiodes are often used for accurate measurement of light intensity in science and industry.
They generally have a better, more linear response than photoconductors. They are also widely
used in various medical applications, such as detectors for computed tomography (coupled with
scintillators) or instruments to analyze samples (immunoassay). They are also used in blood
gas monitors.
PIN diodes are much faster and more sensitive than ordinary p-n junction diodes, and hence
are often used for optical communications and in lighting regulation.
P-N photodiodes are not used to measure extremely low light intensities. Instead, if high
sensitivity is needed, avalanche photodiodes, intensified charge-coupled devices or
photomultiplier tubes are used for applications such as astronomy, spectroscopy, night vision
equipment and laser range finding.
6
2.4
LM317 INTEGRATED CIRCUIT
The introduction of integrated regulator circuits has to a large extent abridged the work
involved in designing the powering unit of a system. This had led to significant save of cost
and as well as increase in the reliability of a system. Every design this day has a wide range
of fixed and adjustable, positive and negative series regulators to choose from as well as an
increasing number of switching regulators. LM317 is a positive variable voltage regulator
device that has a current limiter. The device has all the characteristics common to normal
fixed regulators.
The LM317 series of adjustable three terminal positive voltage regulators is capable of
supplying in the range of 1.5A over a 1.2V to 37V output range. They are exceptionally easy
to use and require only two external resistors to set the output voltage. The LM317 is also
packaged in a standard transistor packages which are easily mounted and handled.
2.5
BASIC CIRCUIT OPERATION
The LM317 device regulators inherently draw as much current as they supply. When this
current is multiplied by the voltage difference between input and output, a significant amount
of power is wasted as heat, this is not just inefficient, but is significant in design consideration;
a heat sink is therefore commonly required. An optional output capacitor can be added to
improve transient response. The adjustment terminal of the regulator can be bypassed to
achieve very high ripple rejection. The output voltage sends a current through the resistor
divider, and the base of the transistor monitors the center of that divider.
Figure LM317 I.C
7
2.6
THE VOLTAGE REGULATOR
The LM317 has three (3) pins; input, output, and adjustment. The device is conceptually an
OP-AMP (with a relatively high output current capacity). The inverting input of the AMP is
the adjustment pin, while the non-inverting pin is set by an internal band gap voltage reference
which produces a stable reference voltage of 1.25V.
A resistive voltage divider between the output and ground configures the OP-AMP as a noninverting amplifier so that the voltage of the output pin is continuously adjusted to be a fixed
amount, the reference voltage, above that of the adjustment pin. Ideally, this makes the output
voltage:
𝑅𝑙
𝑉𝑜𝑢𝑡 = 𝑉𝑟𝑒𝑓 (1 + 𝑅𝑦 ) ________________________a)
Because some quiescent current flows from the adjustment pin of the device, an error term is
𝑅𝑙
added: 𝑉𝑜𝑢𝑡 = 𝑉𝑟𝑒𝑓 (1 + 𝑅𝑦 + IqR1 ___________________b)
To make the output more stable, the device is designed to keep the quiescent current at or below
100µA, making it possible to ignore the error term in nearly all practical cases.
2.7
CURRENT REGULATOR
The device can be configured to regulate the current to the load, rather than the voltage, by
replacing the low-side resistor of the divider with the load itself. The4 output current is that
resulting from dropping the reference voltage across the resistor. Ideally, this is:
𝐼𝑜𝑢𝑡 =
𝑉𝑟𝑒𝑓
𝑅𝐻
_________________________________ c)
Accounting for quiescent current, this becomes:
𝐼𝑜𝑢𝑡 =
2.8
𝑉𝑟𝑒𝑓
𝑅𝐻
+ 𝐼𝑞 _____________________________ d)
ADVANTAGES
The LM317 variable voltage regulator has a built in current limiting and thermal shut down
capacities which makes it short-circuit proof and ideal for any low voltage or homemade bench
8
power supply. The adjustable voltage regulator is the modern standard for voltage regulation
in most power quality applications, it is about 25% higher in cost than the comparable
mechanical voltage regulator, the difference in correction speed often precludes the use of
mechanical units;

Its output voltage regulation is very good,

It has ultra-fast voltage correction speed

It has no restriction on the number of correction cycles

It is versatile as regard its kVA rating, and configuration

It offers a very low or no regular maintenance

It has good line isolation.
The adjustable voltage regulator has poor current overload capacity (except for the series
transformer design)
It is more expensive than the mechanical regulators. The principle drawback of an adjustable
voltage regulator is the limitation impose by the SCR or other power semiconductors and UPS
unit can fail in a matter of hours or days when put in an application with high inrush or overload
current without exercising due precautions.
2.9
TRANSISTOR: The transistor is like an electronic switch. It can turn a current on and
off. A simple way you can think of it is to look at the transistor as a relay without any moving
parts. A transistor is similar to a relay in the sense that you can use it to turn something ON and
OFF. It is used to amplify and switch electronic signals and electrical power. It is composed of
semiconductor material with at least three terminals for connection to an external circuit; the
Base (b), the collector (c) and the emitter (e). And it comes in two versions; NPN and PNP. A
voltage or current applied to one pair of the transistor's terminals changes the current through
another pair of terminals. Because the controlled (output) power can be higher than the
controlling (input) power, a transistor can amplify a signal. Nowadays, some transistors are
9
packaged individually, while many more are found embedded in integrated circuits. The
transistor is the fundamental building block of modern electronic devices, and is universal in
modern electronic systems. Following its development in 1947 by American physicists John
Bardeen, Walter Brattain, and William Shockley, the transistor revolutionized the field of
electronics, and paved way for the construction of cheaper radios, calculators, and computers,
among other things.
The schematic symbol for the NPN looks like this:
Transistor circuit/pictorial view
In a standard NPN transistor, about 0.7v voltage is applied between the base and the emitter to
get the current flowing from base to emitter, this is enough to turn the transistor ON and allow
a current to flow from collector to emitter. They are used as switch and also as an amplifying
device.
2.10
CAPACITOR: A capacitor is a two-terminal, electrical component. Along with
resistors and inductors, they are one of the most fundamental passive components we use.
What makes capacitors special is their ability to store energy; they’re like a fully charged
electric battery. Caps, as we usually refer to them, have all sorts of critical applications in
circuits. Common applications include local energy storage, voltage spike suppression, and
complex signal filtering. When current flows into a capacitor, the charges get “stuck” on the
10
plates because they can’t get past the insulating dielectric. Electrons negatively charged
particles are sucked into one of the plates, and it becomes overall negatively charged. The large
mass of negative charges on one plate pushes away like charges on the other plate, making it
positively charged.
2.11
ZENER DIODE: Zener diode is a PN junction semiconductor device that has been
specially design to have a reverse voltage breakdown at a specific voltage. It has similar
characteristics as that of other common diodes. In breakdown, the voltage across the Zener
diode is close to constant over a wide range of currents thus making it useful as a shunt voltage
regulator. The forward bias region of a Zener diode is identical to that of a regular diode, in the
reverse bias condition the Zener diode is an open circuit and there is only a small leakage
current in the microampere range. As the breakdown voltage is approached the current will
begin to avalanche. The term, breakdown, does not imply destruction but only describes a
region of operation that we utilize. The voltage across the Zener diode in the breakdown region
(also known as the regulation region) is very nearly constant with only a small increase in
voltage with increasing current.
11
Figure : Symbol of a Zener Diode
2.12
RESISTOR: Resistors are components commonly employed in electronic design to
resist the flow of electric current to the required specification. Several types of resistors are
used having different uses and construction. The most common types have a fixed value of
resistance. Various types of fixed resistors are used in circuits, they are the most abundant of
all electronic components and their most common function is to reduce voltages and currents
around a circuit so that ‘active components’, transistors and integrated circuits for instance,
that carry out tasks such as producing or amplifying signals within the circuit are supplied with
the correct voltages and currents to work properly. Resistors are also used in conjunction with
other components such as inductors and capacitors to process signals in many ways. Because
resistors are ‘passive components’ they cannot amplify or increase voltages currents or signals,
they can only reduce them. Nevertheless they are a most essential part of any electronic circuit.
2.13
LIGHT EMITTING DIODE
2.13.1 Sensors: Devices which detect intrusions. Sensors may be placed at the perimeter of
the protected area, within it, or both. Sensors can detect intruders by a variety of methods, such
as monitoring doors and windows for opening, or by monitoring unoccupied.
2.13.2 Passive infrared detectors: The passive infrared (PIR) motion detector is one of the
most common sensors found in household and small business environments. It offers affordable
and reliable functionality. The term passive refers to the fact that the detector does not generate
or radiate its own energy; it works entirely by detecting the heat energy given off by other
objects. As an intruder walks in front of the sensor, the temperature at that point will rise from
room
temperature
to
temperature,
this
quick
change
triggers
the
detection.
2.13.3 Infrasound detectors: The infrasound detector works by detecting infrasound, or
12
sound waves at frequencies below 20 hertz. Sounds at those frequencies are inaudible to the
human ear. Each time a potential intruder tries enter into a house, she or he tests whether it is
closed and locked, uses tools on openings, or/and applies pressure, and therefore he or she
creates low-frequency sound vibrations. Such actions are immediately detected by the
infrasound
detector.
2.13.4 Ultrasonic detectors: Using frequencies between 15 kHz and 75 kHz, these active
detectors transmit ultrasonic sound waves that are inaudible to humans. The ultrasonic detector
operates by the transmitter emitting an ultrasonic signal into the area to be protected. The sound
waves are reflected by solid objects (such as the surrounding floor, walls and ceiling) and then
detected by the receiver. However, a change in frequency will occur as a result of the Doppler
principle, when a person or object is moving towards or away from the detector. Such an event
initiates an alarm signal. This technology is considered obsolete by many alarm professionals,
and is not actively installed.
2.13.5 Microwave detectors: This device emits microwaves from a transmitter and detects
any reflected microwaves or reduction in beam intensity using a receiver. The transmitter and
receiver are usually combined inside a single housing for indoor applications, and separate
housings for outdoor applications.
2.13.6 Compact surveillance radar: Compact surveillance radar emits microwaves from a
transmitter and detects any reflected microwaves. They are similar to microwave detectors but
can detect the precise location of intruders in areas extending over hundreds of acres. With the
capability of measuring range, angle, velocity, direction and size of the target, a CSR is able to
pinpoint a precise GPS coordinate of an intruder.
2.13.7 Photoelectric beams: Photoelectric beam system detect the presence of an intruder by
transmitting visible or infrared light beams across an area, where these beams may be
13
obstructed. To improve the detection surface area, the beams are often employed in stacks of
two or more. However, if an intruder is aware of the technology's presence, it can be avoided.
The technology can be an effective long-range detection system, if installed in stacks of three
or more where the transmitters and receivers are staggered to create a fence-like barrier.
2.13.8 Smoke, heat, and carbon monoxide detectors: Most systems may also be equipped
with smoke, heat, or carbon monoxide detectors. Smoke and heat detectors protect from the
risk of fire using different detection methods. Carbon monoxide detectors help protect from the
risk of carbon monoxide poisoning. Although an intruder alarm panel may also have these
detectors connected, it may not meet all the local fire code requirements of a fire alarm system.
2.13.9 Motion sensors: Motion sensors are devices that use various forms of technology to
detect movement. The technology typically found in motion sensors to trigger an alarm
includes infrared, ultrasonic, vibration and contact. Dual technology sensors combine two or
more forms of detection in order to reduce false alarms as each method has its advantages and
disadvantages.
2.14
SINUSOIDS: A general class of signals used for modeling the interaction of signals
in systems, are based on the trigonometric functions sine and cosine.
14
CHAPTER THREE
METHODOLOGY
3.0
DESIGN AND CONSTRUCTION
3.1
DESIGN MATERIALS AND COST
s/n
Device description
Unit
Per unit price
1
Capacitor
3
250
750
2
Resistor
10
50
500
3
NE555 IC
1
400
400
4
Transistor
1
120
120
5
Vero-board
1
350
350
6
Wire
250
250
7
Casing
1500
1500
8
Soldering tools
2000
2000
3.2 BLOCK DIAGRAM
3.3
CIRCUIT DIAGRAM
15
Amount #
Photo Entry/Exit detector circuit
IR Transmitter circuit
3.4
OPERATIONAL PRINCIPAL
This Photodiode based entry/exit alarm can be used to give a warning alarm sound or signal
when someone passes through a protected or unauthorized area. The circuit is kept standby
through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks,
alarm will be triggered. The circuit uses a PNP Photodiode in the reverse bias mode to detect
light intensity. In the presence of Laser/IR rays, the Photodiode conducts and provides base
16
bias to T1. The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential.
IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable
operates only when its reset pin becomes high. When the Laser/IR beam breaks, current through
the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables
IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated. The
transmitter circuit gives a continuous IR rays, it can emit IR rays up to 5 meters if the IR LEDs
are enclosed in black tubes.
3.5
LED OPERATION
LED circuit operation needs the current to be kept within the device’s specification. The
specified current operation for most LEDs is between ten milliamps to thirty milliamps. This
is referred to as the forward current (If) specification, also the voltage applied to the LED must
be of the correct polarity and of a value that equals or exceeds the LED’s forward voltage (Vf)
specified. The forward voltage rating can be varied from 0.5 to 4.5 volts, depending on the type
of LED used. LED brightness or luminosity is measured in mill-candelas (mcd). Typical,
luminosities are 50-mcd for small LEDs, up to 7000-mcd for the larger ultra-bright LEDs; the
mcd rating is usually measured at a specified current rating, usually 30 milliamps.
3.6
SOLDERING AND FABRICATION
It is a good practice to make a neat soldering of the various components on the Vero-board, in
placing any of the component into the board, I ensured it goes in the right way around and that
it align as supposed. Thereafter I ensured that the leads is bent slightly to secure the part. The
soldering iron is left plugged to power supply to be heated up warmed up for a quick and neat
melting of the soldering lead on the base of the components, the joint is then left to cool for
few seconds. The various components were first tested using voltmeter to ensure its individual
functionality, after which they were assembled based on the circuit diagram on the breadboard.
17
The components were later assembled and soldered onto the Vero-board according to the
designed circuit, each stage of the design was tested and confirm working as required.
18
CHAPTER FOUR
4.0
FUNCTIONALITY TEST
It has been observed that the photodiode which is the major component is very sensitive to any
movement across the door, it gives signal by lighting up the led at either entry/exit position, an
alarm system goes up to create awareness of an entry made through the restricted door. The
Vero - board was tested for continuity, the photodiode was confirmed ok, the stage by stage
connections was tested for continuity, the LED for both entry and exit signal was confirmed
alright.
4.1 RESULT AND DISCUSSION
The photodiode used helps to sense any passage across the door as to indicate a breach, it was
observed that a green light comes up at the verge of entry while a red light show fort at the exit,
the advent of technology has made security challenge a thing of the past since gadgets like this
can be installed at a strategic entry/exit as to monitor its status. This project is straight forward
and less complicated, it should be customized and repackaged into commercial use as to
encourage locally made produce.
19
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
5.1
CONCLUSION
An adjustable voltage regulator is the best choice because it will enable a device to
found access to its rated voltage for operation; it offers two protection circuits found in nearly
all ICs: thermal shutdown and current limiting. While the first is not necessarily needed, as
adding a heat sink can be a suitable substitution, the second provides the fundamental core of
this entire current limiter. The specific IC linear regulator used in this project is the LM317.
This IC is very easy to use, and requires minimal external circuitry to set regulation, in terms
of meeting specifications, the LM317T can operate with an input voltage of as from 3V.The
purpose of this project is to provide and maintain the required voltage across a load.
5.2
RECOMMENDATION
Since the project can solve some security challenges, future project work on this topic should
be extended to counting the number of entry and the number of exit made through a door in a
day. The work should be customize for commercial purpose. The school should have a way of
aiding students whose project work has prospect and has much financial implication.
20
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3. Douglas V. Hall; Microprocessor and Digital systems, second Edition.
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15. MJ11012/MJ11015: 30 A, 120 V, 200 W, high power Darlington complementary pair
BJTs. Used in audio amplifiers, control, and power switching.
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pair.
17. BSP296/BSP171: IGFET (enhancement mode), medium power, near complementary
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22