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worshiprelaxedElectronics - Devices

Nov 2, 2013 (3 years and 7 months ago)

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SHADOW DETECTOR










K. SATHYAPRAKASH RAO

B.E. EIE FINAL YEAR

11099G019

SCSVMV UNIVERSITY




BROAD AREA

This simple project is based on basic electronics leading to the development of a module or an
instrument which can be used in various
applications.

A physical module/instrument is developed which can be used in any surroundings. The
working can be seen by adjusting the circuit according to the surroundings.

ABSTRACT

This is the circuit of a

simple burglar alarm

that produces a loud beep when somebody crosses
a protected area or door.

The circuit is highly sensitive and can detect the shadow of the moving
person from a
distance of 1 meter.


It does not require an aligned light beam to make the circuit
standby. I
t is portable and can be placed anywhere for monitoring.


IC1 is designed as a

voltage comparator
. Its non inverting input is connected to a potential
divider R1 and VR. By adjusting VR, input current to pin3 can be set to a reference level. The
inverting
input of IC1 is connected to a photo diode. IC CA3130 is a
15 MHz BiMOS

Operational amplifier with MOSFET inputs and bipolar output. The inputs contain MOSFET
transistors to provide very high input impedance and very low input current as low as 10pA. It
ha
s high speed of performance and suitable for low input current applications.

CA3130A and CA3130 are op amps that combine the advantage of both CMOS and bipolar
transistors. Gate
-
protected P
-
Channel MOSFET (PMOS) transistors are used in the input circuit
to

provide very
-
high
-
input impedance, very
-
low
-
input current and exceptional speed
performance. The use of PMOS transistors in the input stage results in common
-
mode input
-
voltage capability down to 0.5V below the negative
-
supply terminal, an important attri
bute in
single
-
supply applications.

A CMOS transistor
-
pair, capable of swinging the output voltage to within 10mV of either
supply
-
voltage terminal (at very high values of load impedance), is employed as the output
circuit.

The CA3130 Series circuits opera
te at supply voltages ranging from 5V to 16V,
they

can be
phase compensated with a single external capacitor, and have terminals for adjustment of offset
voltage for application requiring offset
-
null capability. Terminal provisions are also made to
permit
stori
ng

of the output stage. The CA3130A offers superior input characteristics over those
of the CA3130.




AREAS OF APPLICATION

The circuit is an effective instrument with electronic output. Hence the output can be used for
any applications. A few
effective applications are

1.

It can be used in bank

and vault
,

for very high and sensitive security.

2.

It can be used in prison
, home for total lock down. Anyone trying to break through can be
sensed by placing the device in a suitable place.

3.

It can be used as

a sensor device to identify any kind of movement.



















CIRCUIT DIAGRAM







WORKING PRINCIPLE

The circuit uses the light sensing property of the
PIN Photodiode
. The p
-
n junction of the photo
diode gives light current when it is forward
biased.

OP AMP’s non inverting input is connected to a potential divider R1 and VR. By adjusting VR,
input current to pin3 can be set to a reference level.

This VR can be set to any kind of light
ranging from low intensity to high intensity.

Inverting
input of OP AMP is connected to a photo diode.


Normally in the light
(as

set by VR) Photodiode gives voltage to pin2 of OP AMP.

Since this voltage is higher than the voltage set by VR at
pin3, output

of OP AMP remains low
keeping LED and buzzer off.

When

a person approaches the photodiode, the shadow causes a reduction in current through the
photodiode so that voltage at pin2 decreases below that of pin3. Output of OP AMP then goes
high and Buzzer sounds.
















PHOTOGRAPHS













FIG1:
CIRCUIT UNDER TUBELIGHT








FIG2: CIRCIUT RESPONDING TO SHADOW UNDER TUBELIGHT









FIG3: CIRCUIT IN SUNLIGHT









FIG4: SHADOW APPROACHING THE CIRCUIT








FIG5: CIRCUIT RESPONDING TO SHADOW UNDER SUNLIGHT





RESULTS AND DISCUSSIONS

Hence
a circuit which is simple, cheap, efficient and sensitive is developed.

The working and the
response is clearly depicted in the photographs above. Similar to the response under normal tube
light and sunlight, the circuit can be adjusted to any kind of ligh
t by varying the VR. Even in
cloudy days and night times the circuit can be adjust by focusing small amount of light on the
circuit or by adjusting it to the light present. The photodiode detects the changes in the available
light and the circuit will defi
nitely respond.


ADVANTAGES



99% the circuit respond to every possible lighting situation. There cannot be a situation
where the circuit will not work.



That is, it works with minimum light and also with maximum light.



Sensitivity of the circuit increases
with increase in surrounding light
.

NOTE



The circuit triggers when the light intensity changes without a shadow. It is better to keep
the unit in a place where constant light is available



That is, when light in the surroundings changes photodiode responds

to it and buzzer
goes on. So it is necessary to adjust the VR according to the surrounding light