This document describes an automatic night lamp circuit that uses a light dependent resistor to detect low light levels and activate a relay switch to turn on lights. The circuit includes a power supply, resistor, transistor, relay, switch, operational amplifier, and light dependent resistor. When it gets dark, the resistance of the light dependent resistor decreases and allows the transistor to power the relay, which switches on lights connected to it. This allows lights to automatically turn on at night without needing a person to switch them on, saving energy by only powering the lights when it is dark.

1. Presented by:
M.Mounica

2. CONTENTS:
 ABSTRACT
 INTRODUCTION
 CIRCUIT DIAGRAM
 COMPONENTS
 POWER SUPPLY
 RESISTOR
 TRANSISTOR
 RELAY
 SWITCH
 LDR
 ADVANTAGES
 DISADVANTAGES
 APPLICATIONS
 CONCLUSION

3. ABSTRACT:
The following circuit based project can perform this job properly
Automatically turns on when gets dark. This circuit uses the output from
a simple light/dark activated circuit . Drives a relay in its output which
can be further coupled to switch on/off an electrical appliance in a house.

4. INTRODUCTION:
 It is very convenient to light a lamp in our absence in the
evening when it gets dark.
 This circuit can be used to light the staircase light, porch
light etc. using domestic ac supply.
 It is very inexpensive construction and we don’t have to
employ or depend anybody to put on the light when we are
out of station.

5. CIRCUIT DIAGRAM:

6. COMPONENTS:
 POWER SUPPLY
 RESISTOR
 TRANSISTOR
 RELAY
 SWITCH
 OP-AMP
 LIGHT DEPENDENT RESISTOR

7. POWER SUPPLY:
The power supply which is used to covert AC power
to DC power

8. RESISTOR:
 Resistor is a passive component used to
control the current in the circuit.
 Resistance is given by the ratio of voltage
applied across its terninals to the current
passing through it.
 The resistance is measured in ohms.
 Resistors are either fixed or variable.
 The low power resistors are comparatively
smaller in size than high power resistors

9. TRANSISTOR:
 Transistors are manufactured in
different shapes but they have
three leads (legs).
 The BASE - which is the lead
responsible for activating the
transistor.
 The COLLECTOR - which is
the positive lead.
 The EMITTER - which is the
negative lead.

10. RELAY:  Relay is an electromagnetic device which is
used to isolate the two circuits electrically
and connect them magnetically.
 They are very useful devices which allows
one circuit to switch another one while they
are completely separate.
 Relay is a switch that can be divided in to
two parts they are 1.input & 2.output.
 They are often used to interface an
electronic(working at low voltage)to
electrical circuit which is working at high
voltage.

11. SWITCH:
 The most familiar form of switch is a
manually operated electromechanical
device with one or more sets of
electrical contacts, which are connected
to external circuit.
 Automatically operated switches can be
used to control the motions of machines

12. OP-AMP:
 An ideal Operational Amplifier is
basically a three-terminal device
which consists of two high
impedance inputs, one called the
Inverting Input, marked with a
negative or “minus” sign, ( - ).
 The other one called the Non-
inverting Input, marked with a
positive or “plus” sign ( + ).
 The third terminal represents the
Operational Amplifiers output port
which can both sink and source either
a voltage or a current.

13. LIGHT DEPENDENT RESISTOR(LDR):
 An LDR as its name suggests,offers
resistance in response to the
ambient light.
 The resistance decreases as
intensity of incident light increases
an vice versa.
 It is made up of cadmium sulphate.

14.  The unidirectional light, no light diffusing, guarantee
the efficiency of light.
 Light has a unique secondary optical design, lamp light
to the lighting area, further improve the efficiency of the
light, in order to achieve energy saving purpose.
 Light source efficiency is now up to 90-110 lm/W, also
has the very big development space, and the theoretical
value of 250 lm/W.
ADVANTAGES:

15.  Color rendering index is low. Under the light shows the color of the
incandescent light bulbs, not real, it will come up from spectral
distribution analysis, belongs to the technical problems.
 The light spot. Due to the defect on manufacturing process to add
LIGHT and the matching of the reflective glass or lens error, easy to
“yellow” problem.
DISADVANTAGES:

16. APPLICATIONS:
 Domestic Applications
 Military Applications
 Street Light Applications
 Industry Applications

17. CONCLUSION:
By using automatic night lamp we can
save the power because the lights are on
when its gets dark other wise lights are off so
there is no power wastage.

19. ANY QUERIES ?