Automatic Letter Detecting Device for Home Letter Box
(A Project Report submitted in partial fulfillment of the requirements
for the award of)
AMIE
IN
ELECTRONICS AND COMMUNICATION ENGINEERING
AT
Submitted by
Tej Kumar Paliwal
T-146667-8
Under the guidance & supervision of
Dr. Ashok Kumar Jetawat
MIE-061886-6
1
DECLARATION BY STUDENT ABOUT THE ORIGINALITY OF THE WORK
This is certify that the Project work entitled “Automatic Letter Detecting
device for Home Letter Box” submitted by Mr. Tej Kumar Paliwal
(T-146667-8) towards partial fulfillment of the requirements for the award of
the A.M.I.E. in Electronics & communication Engineering is carried out by him
under my supervision and guidance.
As per statement of the candidate this project work has not been submitted for
any degree of AMIE or diploma to any university or institution earlier.
Submitted by
Checked by
Tej Kumar Paliwal
T-146667-8
Dr. Ashok Kumar Jetawat
MIE-061886-6
2
ACKNOWLEDGEMENT
I take immense pleasure in thanking THE INSTITUTION OF
ENGINEERS (INDIA) for the having permitted me to carry out the
project work.
I wish to express my deep sense of gratitude to my project guide Dr.
Ashok Kumar Jetawat (MIE-061886-6) for his valuable guidance and
useful suggestion, which helped me in completing the work in time.
Finally, yet importantly, I would like to express my heartfelt thanks to my
beloved parents for their blessing, my friends/colleagues for their help and
wishes for the successful completion of this project
Tej Kumar Paliwal
3
INDEX
S.NO PARTICULARS
PAGE NO
1
Certificate of Originality by Project Guide
2
2
Acknowledgment
3
3
Title of the project
5
4
Objectives of the study
6
5
Methodology of the study
7
6
Statement of the problem
8
7
Data collection
9
8
Analysis of the collected data
13
19
Result of the analysis
14
10
Detailed methodology of the project
14
11
Structure of the device
21
12
Final Result
28
13
Conclusion
29
14
Scope of future Study
30
15
Reference
31
4
The Project Report
Of
Automatic Letter Detecting Device for Home Letter Box
5
Objective of the study:Man is the only human being that develops the goods for its convenience and luxury. With the
change in technology, manmade machine are going to be automatic. Present days we can says that it
is time of e-mail and internet but still important documents in hard copy and letters are same
importance in the daily life. Now everywhere system is in online forms and it is converting in
online system but also in some work still we cannot replace the paper work. These papers and
documents are needs to post form one place to other place in office and for homes.
In cities where the common men are too busy that they need everything to be done automatically
and conveniently. Peoples don’t have to times to check his home letter box. If he is waiting for
some important documents or letter then also he cannot checked his letter box twice a day that
postman has dropped the letter or not. So we have to make a system that can fulfill above maintain
requirement. So the objective of the study can described in following points.
1.
To make a reliable automatic letter detecting device for home letter box.
2.
To make a device that should be in minimum cost.
3.
The device should be maintenance free means required very low maintenance and very easy to
troubleshoot.
4.
The system can install easily.
So people need an automatic system that gives message or indication for the incoming posts in
conveniences, efficiently and in reliable method. Todays are very price rising so it must be very low
cost. For the fulfillment of this requirement Automatic Letter Box is very suitable electronic device
that is easy to operate and very low cost that can be used in every home.
6
Methodology of the Study:The electronic letter box is a very useful gadget for homes and offices. There are a lot of electronic
systems are available in the market for this purpose but according to our objective here we are using
IC555 based circuits. In this circuit we uses single Monolithic IC555 in dual in line plastic package
with few external components. The main advantage of the letter box is we can find out the presence
and absence of letter inside the box without opening the box.
If someone wants to know whether there is a letter present or not inside the letter box, electronic
letter box device can help him. In this device light depending resistor (LDR) and a white Light
emitting diode (LED) is used as a sensor to detect the presence of letter in the letter box. Thus this
circuit solves the problem of going again and again to the gate of the house to check-up whether a
letter is there in the box or not.
For the indication circuit in the home or in the office, two LEDs, one is green LED and second is
red LED are used to indicate if any letter is present in the letter box or not. When there is no letter
present in the letter box, the green LED will glow. As soon as a letter is put in the box, the green
LED goes OFF, and the red LED will glow.
For the power supply we can use for battery supply or small DC power rectifier. In this circuit is
very less power consumption. There is provision for OFF the system if there is nobody at home or
in the office during holidays. Due to this provision we can reduced its power consumption and also
reduced its chanced of failure.
7
Statement of the Problem:Today’s there a lot of electronic system are available for this type of requirement but these are not
suitable that everybody can afford this types of devices because these are costly, require more care
and complicated. According to our objective for the project we can construct/design different type
of the electronic device for the fulfillment of our requirement but the device should be according to
the following requirement:-
1.
It should be lowest cost.
2.
It should be most reliable during its operation.
3.
It should be maintenance free (require very low maintenance).
4.
It should be easy to troubleshooting if there is malfunction.
5.
It should be easy installation.
The purpose of our project is to fulfillment of the above described requirement. The lowest cost and
reliability is the main requirement because if the system will not be reliable and low cost everybody
cannot afford it. Also it should require very low maintenance otherwise it will be more negative
point for this device. Also it should be easy for troubleshooting. During problem in the device if it
is require expert for repair it, the cost will be automatically increased. So for making described type
of device we collected following data and analyzed it.
8
Data collection:Before the data collection and analysis we should be understand the system analysis and why
system analysis is necessary? During system analysis some activities are carried out, such as
problem definition, design, and implementation. Before designing the actual system/project, we
should know.
1.
What is the problem?
2.
How to solve it?
3.
What are the technical factors required?
4.
What are its features and limitations?
If a system is designed without considering above activities then the system will not work properly
to the satisfaction of user requirement. So system analysis is necessary to design perfect and
accurate system, which satisfies the user requirement.
System analysis is central to the whole of system development. It includes gathering the necessary
data and developing plans for new system. This is not an easy task because many people need to be
satisfied and many conflicts resolved.
The system analyst is the person who guides the analysis, design and implementation and
maintenance of a given system. In performing these four tasks, the analyst must always match the
information system objectives with the goals of organization.
1.
System analyst must determine the requirements of user of a new system so that during
analysis they can discuss with users how to design a new system that meets the requirements.
2.
System analyst has to provide different solutions to the problem, to satisfy user requirements.
9
3.
The system analyst must be a able to find out the details about the system itself. To do this,
the analyst will have to look at such things as forms (input, output formats), data used by the
organization.
4.
System analyst must also be able to work in environments that have considerable ambiguity
and uncertainty.
5.
System analyst must also be creative and imaginative in producing new solutions to meet user
requirements.
Analysis is a detailed study of various operations performed by the system and the relationship
within and outside of the system that is it includes finding out in more detailed what the system
problem are and what are the different new changes the user wants.
After the system analysis next step is the system design. The system design is most creative and
challenging phase of the system design life cycle. Analysis phase is used to design the logical
model of the system and system design the physical model of the system.
For the system design two phases is most important, first is Input and second is Output.
INPUT:In input design stage, which is the part of the system design stage the system analyst has to decide
what inputs are required for the system and prepare input format to give input to the system
according to the requirement. Considering the input to the front end from the user we use the userfriendly simple letter box so that the postman can easily drop the letter or document as usual. Also
the electronic are used in such way that there is very less chance of malfunction.
10
OUTPUT:Output design means that what should be the format presentation of the result. First of all for
designing of various forms to be present in such a way that the user cans easily recognition its result
without confusion.
For the construction of automatic letter box we collected data that what materials and components
are required for the following given both circuits. Both the circuit is best option for us to make the
device. These two types of circuit can be made with low cost, more reliable and very feasible. In
between two, one circuit has speaker output that it’s output or result will come in speaker/buzzer
and in second circuit the output will in the form of small LED glowing whenever we get letter or
documents in the letter box. Both the circuits are as following (fig-3 & fig-4).
11
And following the data are collected that how many components required and what is the cost for
each component. In the following table, both the circuit’s components and their cost are showing.
The cost of the components is showing are average and collected from electronic shops. Table-3 is
showing collected data.
All the data collected are average and in round figure. So we required most suitable in between two.
So, in following table we analyzed these data for selection one circuit that we can make the device.
.
Material required for speaker
output circuit-1.
Material required for LED
Output circuit-2.
S.N.
Components Quantity
Price Rs.
Components
Quantity
Price Rs.
1
LDR
1
15
LDR
1
15
2
LED
1
3
LED
3
9
3
IC555
1
25
IC555
1
25
4
Battery
1
20
Battery
1
20
5
Trimpot
1
10
Trimpot
1
10
6
Resistor
1
2
Resistors
3
6
7
Speaker
1
30
Switch
1
5
8
Switch
2
10
PCB
1
10
9
PCB
1
10
Total price
125
Total price
Table-3 The collected data for required material for project.
12
100
Analysis of collected data:Data are collected and analysis has carried out on the basis of the 5 main requirement terms. These
are reliability, power consumption, failure chance, feasibility and cost. On the basis of these terms
we divided 100 point rating in five parts. There is 20 highest points and 0 is lowest point for each
term. The collected data has analyzed and the following table (Table-4) is showing the analysis.
S.N. Analysis points
Circuirt-1
Rating
Circuir-2
Rating
1
Reliability
It is reliable
20
It is reliable
20
2
power consumption
High, due to speaker
10
Low, due to LEDs
20
Failure chance
High, if no person is
available to OFF the
system, speaker may be
damage
5
Low , If it is not
OFF , then there is
very less chances of
failure of LED
20
10
Good, because of it
shows
only
indication
20
10
Low, 100/-
20
3
4
Feasible
Less, because of it
makes noise
5
cost
high, 125/-
55
Total rating
Table-4 The analysis of collected data.
13
100
The analysis is clearly shown from the analysis-table on the basis of reliability, power consumption,
failure chance, feasibility and cost. So on the bases of rating circuit-1 got only 55 point and
circuit-2 got 100 points.
Results of analysis:We analyzed the collected data and the result of analysis it clear from the table-4 that circuit-2 got
100 points of rating and circuit-1 got only 55 points out of the 100 on the base of five most
requirement. The circuit-1 is got only 5 points in the failure chance that is very low. On this high
failure chance it cannot acceptable.
So the analysis shows that circuit-2 will be more suitable, more cost effective and complete our
requirement of the project. On the analysis base we finalized circuit-2 for the project.
Detailed methodology of Project:The analysis of the data clear the picture the circuit-2 that LED output is more feasible, cost
effective and low failure chances so this circuit is finalized. After finalization of the circuit we
required following components for completion of the device. Hear the list is shown and also their
brief description also written to understand about the used components and their operation.
1.
Light Dependent Resistor (LDR).
2.
IC555 timer integrated circuit.
14
3.
Resistors.
4.
100 K-Ohm variable resistors.
5.
Light Emitting Diodes (LEDs).
6.
Printed Circuit Board.
7.
Battery (9 V).
8.
Switch.
Above maintain electronic components are consumable materials. In the following points there are
briefed description is given for each components which are using in circuit. There description is
necessary because without understanding of the operating principle of electronic components it will
be very difficult for making the device. Also during troubleshooting we cannot traced out its fault.
Description of Components:1.
LDR(Light dependent resistor):-
A Light-dependent resistor (LDR) or photo resistor is a light-controlled variable resistor.
The resistance of a photo resistor decreases with increasing incident light intensity; in other words,
it exhibits photoconductivity. A photo resistor can be applied in light-sensitive detector circuits, and
light- and dark-activated switching circuits. In following fig-5 is showing the symbol of the LDR
and fig-6 is showing actual LDR.
Fig-5 The symbol of LDR
15
A photo resistor is made of a high resistance semiconductor. In the dark, a photo resistor can have a
resistance as high as a few mega-ohms (MΩ), while in the light; a photo resistor can have a
resistance as low as a few K-ohms (KΩ). If incident light on a photo resistor exceeds a
certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to
jump into the conduction band. The resulting free electrons (and their holes partners) conduct
electricity, thereby lowering resistance [2].
Fig-6 Actual figure of LDR.
2.
IC 555:-
The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation,
and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as
a flip-flop element. Derivatives provide up to four timing circuits in one package. The following
fig-7 is showing pin diagram of IC555 and fig-8 is showing the actual diagram of IC. The whole IC
is in 8-pin package. The description of pins is GROUND, TRIGGER, OUT, RESET, CONTROL,
THRISHOLD, DISCHARGE and Vcc from pin 1 to 8 respectively.
16
Fig-7 Pin diagram of IC555
Fig-8 actual fig of IC555
Modes of application:The 555 has three operating modes:1.
A-stable multi-vibrator
2.
Mono-stable multi-vibrator
3.
Bi-stable multi-vibrator
In this application we are using bi-stable multi-vibrator operation. In bi-stable (also called Schmitt
trigger) mode, the 555 timer acts as a basic flip-flop. The trigger and reset inputs (pins 2 and 4
respectively on a 555) are held high via Pull-up resistors while the threshold input (pin 6) is simply
floating. Thus configured, pulling the trigger momentarily to ground acts as a 'set' and transitions
the output pin (pin 3) to Vcc (high state). Pulling the reset input to ground acts as a 'reset' and
transitions the output pin to ground (low state). No timing capacitors are required in a bi-stable
configuration. [3].
17
3.
Resistors:-
A resistor is a passive two-terminal electrical component that implements electrical resistance as a
circuit element. Resistors act to reduce current flow, and, at the same time, act to lower voltage
levels within circuits. Resistors may have fixed resistances or variable resistances. The resistor
work on Ohm’s law.
4. 100 k-ohm variable resistor:A Variable resistor informally is a three-terminal resistor with a sliding or rotating contact that
forms an adjustable voltage divider. In this type of resistor only two terminals are used, one end and
the wiper, it acts like a potentiometer. Figure-9 is showing the symbol of the variable resistance and
fig-10 is showing actual figure of 100 K-Ohm variable resistor [4].
Fig-9 Symbolic diagram of variable resistor
The 100 k-ohm variable resistor is also called at trimmer or trimpots that is shown in following
figure (fig-10).
Fig-10 Trimpot or variable resistor [5]
18
Operation of trimpot in the circuit:The trimpot or trimmer is a variable resistor that used when adjustment of resistance according to
the circuit is required. The following points are explaining that how to used the trimpots when we
required the adjustments of the resistor according to the circuit operation.
1.
If we take terminal A and terminal B, and rotate the movable metal in clockwise direction, the
resistance of preset increases from 0 to maximum. As we move the metal in anticlockwise
direction, the resistance decreases.
2.
If we take terminal A and terminal C, and rotate the movable metal in anticlockwise direction,
the resistance of preset increases from 0 to maximum. As we move the metal in clockwise
direction, the resistance decreases [5].
5.
LED (Light Emitting Diode):-
A light-emitting diode (LED) is a two-lead semiconductor light source. It resembles a basic pnjunction diode, which emits light when activated. When a fitting voltage is applied to the
leads, electrons are able to recombine with electron holes within the device, releasing energy in the
form of photons. This effect is called electroluminescence, and the colour of the light
(corresponding to the energy of the photon) is determined by the energy band gap of the
semiconductor.
LEDs have many advantages over incandescent light sources including lower energy consumption,
longer lifetime, improved physical robustness, smaller size, and faster switching. Typical indicator
LEDs are designed to operate with no more than 30–60 mill watts of electrical power. All these
types of advantages are required in our project so we selected LEDs for our circuit. Fig-11 shows
symbol of a LED [6].
19
Fig-11 symbolic diagram of LED
6.
PCB (printed circuit board):-
A printed circuit board (PCB) mechanically supports and electrically connects electronic
components using conductive tracks,
pads
and
other
features etched from
copper
sheets laminated onto a non-conductive substrate. Printed circuit boards are used in all but the
simplest electronic products. Manufacturing circuits with PCBs is cheaper and faster than with
other wiring methods as components are mounted and wired with one single part. Furthermore,
operator wiring errors are eliminated.
7.
Battery (9V):-
The most common form of 9 V batteries is commonly called the transistor battery which was
introduced for the early transistor radios. It has a rectangular prism shape with rounded edges and a
polarized snap connector at the top. This type is commonly used in pocket radios and other small
electronic devices. They are also used as backup power to keep the time in certain electronic clocks.
8.
Switch:-
Switch is used in both electrical circuit and electronic. These are simple circuit breaker. There is no
any polarity selection so they can directly fix in series. During ON condition circuit completed so
current can flow through the circuit and during OFF condition it break the circuit so it stop the
current.
20
Structure of the device:As the result of analysis we selected circuit-2 for our project. The structure of circuit for the project
device is according to the following figure of electronic circuit diagram (fig-12). For the device its
electronic circuit is constructed on one PCB. One IC555’s base mounting is soldered on PCB and
IC555 is fixed on that base mounting. The base mounting should be used during any integrated
circuit installation so that if any problem comes in that IC then we can replace this IC without
removing of its soldering.
The construction diagram of automatic letter detecting device is shown in fig-13. In the device
IC555 pin no. 4, 6, and 8 are shorted on one terminal on PCB for power supply connection. As we
can see in the figure-13, for letter detection one letter box is made and in this letter box, one LDR
is fixed on one side of wall of the box and its one terminal termination has done to the power supply
positive point and it’s second terminal is connected to the IC555 pin-2. On the other side wall of
box, one white LED is fixed and its one terminal (positive terminal) is connected to the LDR
21
positive supply terminal and second terminal (negative terminal) is connected to resistor (470 Ω)
which is fixed on the PCB. The resistor (470 Ω) is for white LED operation. The second terminal of
this resistor connected to the negative power supply terminal on the PCB. These both positive and
negative supply terminals are connected to the 9V battery by snap terminal. In this mesh, one
switch is connected in series for ON/OFF the system.
Now one variable resistor of 100 KΩ is soldered on the PCB and its port ‘A’ is connected through
connecting wire to the IC555 pin-2 and its port ‘C’ is connected to the IC pin-1. The IC pin-1 it
soldered to the negative point of power supply through connecting wire.
Both the indicator LED (green and red LED) lights are fixed on one board with resistor 470 Ω. The
green LED’s positive terminal is connected to the positive supply terminal and its other terminal is
connected to the output point of the IC555. The red LED’s positive terminal is connected to the IC
output pin (pin-3) and its negative terminal is connected the negative terminal of the power supply
terminal.
The following figure (fig-13) is shown the actual construction of the device. All the components are
fixed on the cardboard. The PCB circuit is open from back side so it is mounted on one thermocol
block to avoid short circuit. All connecting wires are in different colours so that we can recognize
during any troubleshooting. Also it is easy to termination or soldering.
For battery termination to the device we fixed one snap terminator to the 9V battery in series with a
switch so we can ON and OFF the device. Also replacement of battery is easy to disconnect the
snap to the battery. Battery is tightly fixed on the cardboard with the help of insulation tape that
cannot move during handling of device. And its switch is rigidly fixed on the card board with the
help of nail so that it properly operated also convenient for the user during ON and OFF.
22
Fig-13 Model of automatic Letter detecting device.
Adjustment of the 100 KΩ resistor:For the proper operation of the device is completely depends upon the switching operation of the
IC555. And the switching input is coming through the LDR. When the resistance of the LDR is
changed during light and cut-off of light which is coming white LED. When letter is present in the
box it obstructs light to LDR or letter is not in the box then light fall on the LDR, due to these
action LDR current changes and detects by the IC555 input pin-2 when the variable resistor has on
its certain resistance.
For the adjustment of this resistor first of all we ON the device’s switch. When supply is ON then
it would either green ON or red ON. If its green LED is on then it is ok otherwise takes a small
screwdriver and turn that variable resistor in clockwise direction or anticlockwise direction till the
green LED not ON. When green LED is ON then put any letter type obstacle in the letter box so
that LED light not reach to the LDR.
23
Due to this LDR resistance changed from K-ohm (KΩ) to mega-ohm (MΩ) and current decreased
in the IC555 input. Through this, switching action happens and red LED glows.
After doing this, if red LED not glow then again adjusted the 100 KΩ variable resistor just anti
direction that done before till red LED glow. Now the device is ready for the operation. The
adjustment operation is showing in following figure (fig-14).
Fig.-14 The adjustment of the 100 KΩ variable resistor
Operation of the device:The device operation is simple. First of all we ON the power supply through switch, when there is
no any letter in the letter box, variable resistor’s resistance in K-ohm so through switching
operation on the IC the output of the IC is low so that it’s green LED will be forward bias and red
LED is in reversed bias so that green LED is glow and red LED is in OFF condition. When green
LED is glow it means that there is no letter in the letter box. The operation is showing clear in the
following figure (fig-15) that there is not any letter in the box so it green LED is glowing.
24
Fig-15 Operation-no letter in the letter box.
Now put the letter in the box, the light which was falling on the LDR from white LED got
obstructed through letter so the resistance of the variable resistor changed from k-ohm to mega-ohm
approximately and current decreased through this input to IC and switching action of IC happen so
that it’s output voltage from low to high due to this green LED circuit changed from forward bias to
reversed bias and the red LED’s circuit changed from reversed to forward. Results the green LED
goes OFF and red LED goes ON. This shows that letter is present in the letter box in the following
figure (fig-16).
Also we have counter checked its operation. Again we removed letter from the letter box, according
to switching operation green LED ON and instantly red LED goes OFF. This operation shown in
the following figure (fig-17).
25
Fig-16 Operation-letter present in the letter box.
Fig-17 counter checked the device again removing letter.
Precautions during making and operation of the device:The following precautions should be take care during the operation and construction of the device.
All these precaution is necessary for proper operation of the device and also safety for the user.
Power supply of the device can also give through rectifier. It works on AC supply so we should be
careful during maintenance on that one
26
1.
The IC555 should not solder on the PCB directly. Its base mounting should be solder on the
PCB then IC should be fixed on the mounting so that if there is any problem in the IC then we
can easily replaced it without unsolder it.
2.
The letter box is made in such way that if there is letter in the box then LDR would not get
light from the white light and operate without malfunction.
3.
Battery should be connected through the snap terminal so that after discharging it we can
replace it easily.
4.
If we are not using battery and using rectifier of 230V AC to 9V DC convertor then it very
necessary that there should not any short circuit condition and proper insulation should be
provides.
5.
If we have to work on the rectifier then it should be done with proper isolation.
6.
There should always be a switch in series with power supply connection so that if system is
not in use, we can OFF it, for energy saving.
7.
Connecting wire should be in different color so it is easy during maintenance or
troubleshooting.
8.
To avoid short circuit of the device we should applied insulation on its live terminals.
9.
Indicator LED should be in different color so that recognition will be easy.
All above maintains points should be kept in mind during construction of the device for fulfillment
of our requirements. These all precautions are for the safety if we are using any rectifier for the
power supply for the device because of if we are using rectifier of 230V AC to 9V DC then safety
of the equipments and also safety of users are very necessary.
27
Soldering on the PCB is very fine and precise work. And if the soldered components are IC’s then
work should be done very carefully because of shorting of IC’s pins will create serious malfunction
during the operation of the device. The shorting may be through small soldering wire piece that
cannot be easily seen. The same problem I faced during making of this model that the device was
not working according to the circuit and it was very difficult to trace out the fault.
The adjustment of the variable resistor should be done through small screw driver so that chances of
damage can be avoided. One more thing that the whole device circuit is open condition so it should
be protect from water because water can make short circuit.
FINAL RESULTS:According to our objective and selected problem, we collected related data to solve it, analyzed
these data and got the one result that how to solve the problem. We selected one circuit and made
the device according to the circuit and precautions needs. The constructed devise circuit variable
resistor has adjusted according to the required resistance.
The device has been checked with applying letter in the letter box, the device worked according to
the circuit design and our requirement. When we ON the power supply of the device, there was not
any letter in the letter box so we find out that its green LED was glowing. Then we put one letter in
the letter box so that on the output portion its red LED was glow. According to our design it is
correct output.
We also counter checked it operation by removing the letter from the letter box at that time it’s red
LED goes OFF and instantly it green LED glow again.
28
CONCLUSION:We took one problem and researched on this problem and find the solution by making the device.
And the objective was that the device should be reliable, cost effective, easy to operate and required
low maintenance. As the final result, the device has performed according to our design and
requirement. The following points may clears as a conclusion of the project.
1.
We selected one circuit that was more cost effective between two.
2.
It was easy to construction.
3.
It was operated according to our requirement.
4.
It was more reliable.
5.
It troubleshooting is easy whenever problem comes.
The conclusion of our project is that the device is very reliable. There is very less chance of failure
due to its robust design. If there is a letter in the box it will be detected. So the reliability point of
view it is perfect. On the other hand it is very low cost because the components are using for
making this device we can purchase on small electronic shop. Its circuit is very simple and can be
understand easily.
Also its failure chances it very low due to it is operating on the 9V DC (battery power). Also LED’s
are more reliable then speaker. It can be OFF during nobody in home or in office just to OFF the
switch.
On the troubleshooting or maintenance point of view it is very simple so can easily be short out its
problem. Now we can say that it is according to our requirements.
29
SCOPE OF FUTURE STUDY:This is very cost effective so it can be produced on mass level and also its circuit is very simple so
it can be imbedded on single chip that it may installed in every home.
It switching circuit can also be used for automatic door open/close. For door open/close we can use
its LDR and LED sensing system in any gallery in front of door that if anybody comes in front of
LDR then it detected that person like automatic letter detecting box and give the switching signal.
Through this signal we cam motorized it and open/close the door.
This circuit also can take by more modification for light on/off of the rooms if person enter in the
room. The same LDR circuit can detect the entry and it circuit can on/off the light of the room.
Furthermore we can also use this circuit with modification in automatic water tap making. It
operation can be in such way that user take his hand for washing under the tap this circuit sense it
presence and start/stop the tap. This tap operation can be controlled through solenoid valve.
There is a lot of scope in this circuit for further study. This may make very convenient of daily life.
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Reference:[1]
www.circuiteasy.com/electronic-letter-box/ (Access zone 08 July 2014)
[2]
www.en.wikipedia.org/wiki/photoresistor (Access zone 08 July 2014)
[3]
www.en.wikipedia.org/wiki/555-timer-IC (Access zone 10 July 2014)
[4]
www.en.wikipedia.org/wiki/trimmer-(electronics) (Access zone 12 July 2014)
[5]
www.buildcircuit.com/how-to-use-variable-resistor/ (Access zone 16 July 2014)
[6]
www.en.wikipedia.org/wiki/Light-emitting-diode (Access zone 16 July 2014)
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