GOOD
MORNING
SUN-
UP
ALAR
Team Members:
V.S.SWAMINATHAN
M
VINAYAK.R.BANVI
VANDANA
ASHWINI
ARCHANA
INTRODUCTION:
The name of the project itself suggest that it
is something related to the sun or light.
We all know that the radiations from the sun
or the solar energy is used in various day to
day life applications .
Our project is designed in such a way that it
can detect even a very small amount of light
which is indicated by the output buzzer.
The sun up alarm can be used to provide an
audible alarm.
The main principle is that -When the sun beam or light falls on
a photo-resistor there is a voltage drop across the resistor and
then the alarm can be heard via the piezo buzzer.
CIRCUIT DIAGRAM:
COMPONENTS:
Sl.no Components Quantity Description
1. Transistor 1
NPN Q1 2N2222
2. Photo resistor 1
(Cds)
3. Resistors 4
a)100k(R1,R2) 2
b)10k(R3) 1
c)4.7k(R4) 1
4. Piezo Buzzer 1
5. 741 Operational 1
Amplifier
BRIEF DESCRIPTION OF THE COMPONENTS:
1. Transistor:
The 2N2222, often referred to as the ‘Quad Two’ transistor, is a small NPN
transistor used for general purpose low-power amplifying or switching
applications.
2. Photo Resistor:
It is a light dependent or a cadmium sulphide cell (cds)
It is a resistor whose resistance decreases with the increase in intensity of
light.
The inexpensive cds are found in many consumer items such as camera
,light meters, street lights, clock radios, alarms and outdoor clocks.
continued…
3. Resistors:
A resistor is a two terminal electronic component that produces a
voltage across its terminals that is proportional to the electronic
current through its in accordance with ohms law V=IR.
4. Piezo Buzzer:
A piezo buzzer converts electrical signals into sound by using a piezo electric
crystal element in it, which deforms slightly when voltage is applied to it.
This crystal element is connected to a speaker cone or panel, which vibrates
quickly when a rapidly changing voltage is applied.
This vibration in turn sets up sound waves in the air , thus generating a tone
at a frequency based on the frequency of the voltage wave.
continued…
5. 741 Op-Amp :
• An Op-Amp is a DC coupled high gain electronic voltage with differential
Inputs and usually a single output.
• The Op-Amp is basically one type of differential amplifier.
• High input impedance at input terminals (ideally infinite) and low output
impedance (ideally zero) are important.
• The output of the op-amp is controlled either by –ve feedback which largely
determines the magnitude of its output voltage gain or by +ve feedback
which facilitates regenerative gain and oscillation .
• The amplifiers differential inputs consists of v+ input and v- input where v+
input is the voltage at the non inverting terminal and v- is the voltage at
inverting terminal.
• Op-amp has two inputs inverting pin2 non inverting pin3 the op-amp has one
output pin 6
Continued…
If the voltage goes into pin 2 then it is known as inverting amplifier . If the
voltage goes into pin 3 it is non inverting amplifier.
• The circuit above it can be seen that we have used non inverting amplifier.
However in the logic diagram of sun up alarm the 741 amplifier act as
comparator and not an amplifier.
• Though the 741 act as comparator it still detects the weak signals so that they
can be recognized more easily.
• Positive voltage is referred as high and negative voltage is referred as low .
WORKING:
• This circuit is for a simple buzzer that is activated by light, i.e., the buzzer is
on when there's ample light and off when it is dark.
• A general-purpose operational amplifier, the 741, is used as a comparator
that determines whether there's enough light to turn on a self-oscillating
piezoelectric buzzer.
• The comparator compare two voltages and produce a signal that indicates
which voltage Is greater .
With respect to the diagram, if v1 is
greater than v2 then the difference will
be positive and the result will be
amplified to +vcc.
If v2 is greater then the difference is –ve
and the result will be amplified to –vcc.
If both the voltages are equal then the
output =difference=zero
• Its non-inverting input is connected to a photo resistor, a component whose
resistance decreases as more light shines on it. Its inverting input, on the other
hand, is connected to an almost fixed voltage, i.e., a proportion of the supply
voltage as set by trimmer resistor R2.
• If there isn't enough light shining on the photo resistor, the buzzer is quiet. As
more light shines on the photo resistor, its resistance decreases and causes the
voltage across R1 to increase
• At a certain level of lighting, the voltage across R1, which is also the voltage at the
non-inverting input of the 741, becomes larger than the voltage at the inverting
input.
• At this point, the 741 is triggered to output a 'high' level, turning on Q1. Q1 then
activates the self-oscillating piezoelectric buzzer.
Applications:
Sun-up alarm is used to provide an audible alarm when the sun comes up.
It can be used in dark areas to detect light beams.
Sun-up alarm is expected to construct a safe place for any precious items.
Sun-up alarm is often used to detect head lights of the automobiles.
THANK
YOU
