This document describes the design of an automatic night lamp using a logic circuit. It includes an introduction describing the purpose and advantages of the system. It then provides a 3 sentence summary of each main section: principles, block diagram, circuit diagram, component descriptions, components used, practical implementation, working, uses, conclusions and applications, and bibliography. The system uses a light dependent resistor and transistors to automatically turn the lamp on when it gets dark and off when it is light outside. It can reduce energy consumption and errors from manual operation.

1. TO DESIGN THE AUTOMATC NIGHT
LAMP USING LOGIC CIRCUIT
A COMPLETE PROJECT REPORT SUBMITTED AS A
PART FOR FULFILLMENT OF DIPLOMA
ENGINEERING IN 3 YEARS
IN
ELECTRONICS AND TELECOMMUNICATION
ENGINEERING

2. CONTENTS:
1 Introduction.....................................................................1-2
2 Principle............................................................................3-4
3 Block diagram....................................................................5-6
4 Circuit diagram..................................................................7-8
5 Component Description......................................................9-23
a. LDR
b. Transistor BC547
c. Transistor BT136
d. Resistance 10kΩ
e. Lamp 230 volt
f. 6 volt Battery
6 Component used in Circuit.................................................24-25
7 Practical.............................................................................26-27
8 Working.............................................................................28-29
9 Uses of this project.............................................................30-31
10 Conclusion & scope..........................................................32-34
Application1
Application2
11 Bibliography.......................................................................35-36

3. 1.INTRODUCTION

4. Automatic light control system is a simple and powerful concept, which uses
transistor as a switch to switch ON and OFF the light automatically. By using this system
manual works are removed. It automatically switches ON light when the sunlight goes below
the visible region of our eyes. It automatically switches OFF light under illumination by
sunlight. This is done by a sensor called Light Dependant Resistor (LDR) which senses the
light actually like our eyes.
By using this system energy consumption is also reduced because now a-days the
manually operated lights are not switched off properly even the sunlight comes and also not
switched on erlier before sunset . In sunny and rainy days, ON time and OFF time differ
significant which is one of the major disadvantage of using timer circuit or manual operation.
This project exploits the working of a transistor in saturation region and cut-off region
to switch ON and switched OFF the light at appropriate time with the help of an
electromagnetically operated switch.
Automatic light needs no manual operation of switching ON and OFF. The system it
self detects whether there is need for light or not. When darkness rises to a certain value then
automatically light is switched ON and when there is other source of light, the light gets OFF.
The extent of darkness at which the light t be switched on can also be tailored using the
potentiometer provided in the circuit.
Moreover, the circuit is carefully designed to avoid common problems like overload,
relay chattering and inductive kick in relay.

5. 2.Principle:

6. The automatic light control system operates on 230v AC supply. The automatic light
controller has a photoconductive device whose resistance changes proportional to the extent
of illumination, which switches ON or OFF the with the use of transistor as a switch.
Light dependent resistor, a photoconductive device has been used as the transducer to
convert light energy into electrical energy. The central dogma of the circuit is that the change
in voltage drop across the light dependent resistor on illumination or darkness switches the
transistor between cut-off region or saturation region and switches OFF the light.

7. 3.Block Diagram

8. Automatic Night Lamp With Block Diagram

9. 4.Circuit Diagram

10. The circuit diagram of automatic light
controller is given below:

11. 5.Component Description

12. 5.a.Light Dependent resistor (LDR)
A light dependent resistor is a resistor whose resistance changes with the intensity of
incident light.
The working principle of light dependent resistor is photoelectric effect. A light
dependent resistor is made of a high resistance semiconductor. If the energy of the incident
light is greater than the band gap of the semiconductor, electron-hole pairs are generated .The
photo generated electron-hole pair transits the device giving rise to photo conductivity.
The essential elements of a photoconductive cell are the ceramic substrate, a layer of
photoconductive material, metallic electrodes to connect the device into a circuit and a
moisture resistant enclosure. Light sensitive material is arranged in the form of a long strip
Zigzagged across a disc shaped base with protective side. For additional protection, a glass or
plastic cover may be included. The two ends of the strip are brought out to connecting pins
below the base as shown below.
The commercial photoconductive materials include cadmium sulfide (Cds), cadmium
selenide (Cdse), lead sulfide (Pbs) and Indium antimonide (InSb) etc., There is large change
in the resistance of a cadmium selenide cell with changes in ambient temperature, but the
resistance of cadmium sulfide remains relatively stable. Moreover, the spectral response of a
cadmium sulfide cell closely matches to that of a human eye. Hence, LDR is used in
application where human vision is a factor such as street light control or automatic iris
control for cameras. The above mentioned features drive us to opt for CdS based LDR in our
electronic circuit for automatic controller.

13. LDR

14. 5.b.Transistors BC547

15. NPN Exitaxial silicon Transistor
Symbol Parameter
Value
Unit
VCBO CollectorBase Voltage :BC547 50 V
VCEO CollectorEmitterVoltage :BC547 45 V
VEBO EmitterBase Voltage :BC547 6 V
IC CollectorCurrent(DC) 100 mA
PC CollectorPowerDissiption 500 mW
TJ JunctionTemperature 150 O
C
TSTG Stronge Temperature ~65~150 O
C
Transistor are three terminal active device made from different semiconductor materials
that can act as either an insulator or a conductor by the application of a small signal voltage.
The transistor’s ability to change between these two states enables it to have two basic
functions: switching or amplification. Then bipolar transistors have the ability to operate
within three different regions:
 Active region – The transistor operates as an amplifier and IC=βIB
 Saturation – the transistor is fully-ON operating as a switch IC=Isaturation
 Cut of transistor is “fully-OFF” operating as a switch and IC= 0
The word Transistor is an acronym, and is a combination of words transfer Resister used
to describe their mode of operation way back in there early day of development. There are
two basic type of bipolar transistor construction, NPN and PNP, which basically describes the
physical arrangement of the P-type and N-type semiconductor materials from which they are
made.
A transistor is made of a solid piece of semiconductor material, with at least three
terminals for connection to an external circuit. The bipolar junction. Transistor basic
construction consists of two PN-junctions producing three connecting terminal with each
terminal being given a name to identify it from the other two. These three terminals are
known and labelled as the Emitter (E), the base (B) and the collector (C) respectively.
Bipolar transistors are current regulating devices that control the amount of current
flowing through them in proportion to the amount of biasing voltage applied to their base
terminal acting like a current- controlled switch. The principle of operation of the two
transistor types NPN and PNP, is exactly the same the only difference being in their biasing
and the polarity of the power supply for each type.

16. Bipolar Junction Transistor Configurations
Since bipolar junction transistor is a three terminal device, there are basically three
possible ways to connect it within an electronic circuit with one terminal being common to
both the input and output. Each method of connection responding differently to its input
signal within a circuit as the static characteristics of the transistor varies with each circuit
arrangement.
 Common base configuration – has Voltage gain but no current gain.
 Common Emitter configuration– has both current and voltage gain.
 Common collector configuration – has current gain but no voltage gain

17. NPN transistor configuration
The construction and terminal voltages for an NPN transistor are shown
above. The voltage between the base and emitter (VBE) is positive at the base and
negative at the emitter because for an NPN transistor, the base terminal is alwys
positive with respect to the t5or emitter. Also the collector supply voltage is positive
with respect to the Emitter (VCE). For an NPN transistor to conduct, the Collector is
always more positive with respect to both the base and the Emitter.
The voltage sources will be connected to an NPN transistor as shown above. The
collector is connected to the supply volotage VCC via the load resistor, RL which also acts to
limit the maximum current flowing through the device. The Base suppy voltage VB is
collected to the Base resistor RB, which again is used to limit the maximum Base current.

18. Typical Characteristics

21. 5.c.TRANSISTOR BT 136
General Description
Glass passivity triacs in a plastic envelop, intended for use in applications requiring
high bidirectional transient and blocking voltage capability and high terminal cycling
performance. Typical applications include motor control, industrial and domestic lighting,
heating and static switching.
Syambal Parameter Max Max Max Unit
BT136- 500 600 800
BT136- 500F 600F 800F
BT136- 500G 600G 800G
VDRM Repetive peakoff-statevoltage 500 600 800 V
I T(RMS) RMS on-state current 4 4 4 A
ITSM Non-repetitive peakon-statecurrent 25 25 25 A

23. 5.d.RESISTANCE 10KΩ
Resistors are the most common passive electronic component (one that does not
require power to operate). They are used to control voltage and currents. While a resistor is a
very basic component, there are many ways to manufacture them. Each style has its own
characteristics that make it desirable in certain types of application. Choosing the right type
of resistor is important to making high-performance or precision circuits work well.
All resistors are basically just a piece of conducting material with a specific value of
resistance. For that piece of conducting material to be made into a practical resistor, a pair of
electrodes and leads are attached so current can flow. The resistor is then coated with an
insulating material to protect the conducting material from the surrounding environment and
vice versa. There are several different resistor construction methods and body styles (or
package) that are designed for a certain range of applied voltage, power dissipation, or other
considerations. The construction of the resistor can affect its performance at high frequencies
where it may act like a small inductor or capacitor has been added, called parasitic inductance
or capacitance.

24. 5.e.Lamp 230 Volt

25. 5.f.Battery 6Volt
Battery 6 volt external using circuit because circuit positive and negative 6 volt urgent.

26. 6.Component used in Circuit

27. S.NO COMPONENT NAME NOS RATING
1 LDR 1 NO RATING
2 TRANSISTOR 1 BC547
3 TRANSISTOR 1 BT136
4 RESISTANCE 1 10KΩ
5 LAMP 1 230VOLT
6
6
BATTERY 1 6 VOLT

28. 7.Practical Circuit

29. At first LDR Open no light fire.
Next Time LDR Cover light fire
PCB standards for circuit board. It is a type of connecting system through which we
can give a compact look of our project. The board covered with copper strip. This design
depend upon the user.

30. 8.Working

31. The alternating current voltage (220 V) is stepped down to (6V) using. The stepped
down AC voltage is to obtain a constant ripple-free DC voltage, is used across the circuit.
In dark, the resistance of light dependent resistor is high. So, the voltage drop across
the light dependent resistor is also high. Now the output of the NAND gate N1 is low since
both the input signals are high, which makes the switch SW1 to remain open and now the
output from NAND gate N2 becomes high since both the input signals are low. The high
output signal from the N2 terminal device transistor to the saturation region, which makes the
collector current IC very high. Finally, the high collector current flowing through. When a
light of suitable intensity is incident on the light dependent resistor, the resistance decrease
and the voltage drop across the light dependent resistor is low. Now the output of the NAND
gate N1 is high since one of the input signal is low and the other one is high, which makes to
close and now the output from NAND gate N2 becomes low since both the input signals are
high. The low output signal from the N.
Terminal device transistor to the cut-off region. In this case, the collector current is
not high enough to make the Lamp glow, since other circuit elements such, Lamp and resistor
are connected in parallel to each other.
Thus, the toggling the transistor between cut-off region and saturation region it is
possible to switch OFF or switch ON the Lamp. In this circuit, BC547 transistor is employed
to increase the collector current The extent of darkness or the intensity of light at which the
light should switch ON or OFF can be turned by adjustint.

32. 9.Uses of this project

33. By employing this circuit energy consumption can be reduce considerably as the
switches ON or OFF automatically in appropriate time. Moreover, errors which occur due to
manual operation also can be eliminated completely. The Automatic street light controller
unit fabrication is cost-effective with good sensitivity and high reproducibility. Moreover, the
construction of the circuit is also simple so that it can be done easily as it involves locally
available component. The circuits designed in such a way that the extent of darkness at which
the light has to switch ON or OFF also can be tailored whenever it is needed. It can be used
for other purposes like garden lighting balcony lighting etc.

34. 10.Conclusion & scope

35. Application1:
The above circuit can be powered from a battery, which can be charged during day
time by harvesting the solar energy through solar cell as shown below:

36. Application 2:
The solar energy harvested from sunlight can be stored, inverted from DC voltage to
AC voltage using sun tie converted. The AC voltage can be stepped up and given to The
Electric grid.
The AC voltage Form The electric Grid can be stepped down, rectified and used for
powering the circuit. Meanwhile, the street can also be powered by the AC voltage, which is
controlled by a relay switch connected to the switching part of the circuit. The above
mentioned strategy will be enabling us to harvest solar energy in an effective way for the
operation of the circuit and for powering the street light also.

37. 11.Bibliography

38. Here are some various sites from where we collect some of important information related.
Project are
1) www.ieee.org/about/reserch/2010_project cts. html
2) www.wikipedia.org
3) www.tutorialpoint.com
4) www.made-in-china.com
5) www.globalmaret.com
6) www.red100.org
7) www.alibaba.com
8) www.electronicforyou.com
9) www.electronics-tutorials.com
10)www.circuitstoday.com