Application of logic gates and designing of the basic circuits in an innovative way, like anti-theft alarm and fire alarm

1. IIEST, SHIBPUR 1

2. IIEST, SHIBPUR 2
Group 7
Group Members
Devayan Basu 510614002
Rumani Chakraborty 510614011
Sayan Sen 510614046
Shamik Basak 510614063
Poushali Ray 510614064
Sandip Guhathakurta 510614065
Semester Fourth
Session 2015-2016

3. Introduction
 Two types of signals: one is analog or continuous signal and the second one is digital or
discrete signal. So the science or field of research in the area of engineering is termed as
Analog and Digital Electronics respectively.
 Digital electronics are those electronics systems that use a digital signal instead of an analog
signal. They are the most common representation of Boolean algebra and are the basis of all
digital circuits for computers, mobile phones and numerous other consumer products.
IIEST, SHIBPUR 3

4. IIEST, SHIBPUR
 The most common fundamental unit of digital electronics is the logic gate. By combining
numerous logic gates (from tens to hundreds of thousands), more complex systems can be
created. The complex system of digital electronics is collectively referred to as a digital
circuit.
 It is essential to understand wide range of applications from industrial electronics to the
fields of communication, from micro embedded systems to military equipment. The main
(and perhaps, the most revolutionary) advantage of digital electronics is the decrease in
size and the improvement in technology.
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Introduction

5. IIEST, SHIBPUR
5V Regulated Supply
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 The LM7805 is a positive voltage regulator IC while the LM7905 is a negative voltage
regulator IC.
 The circuit is using a 230V AC to 6V-0-6V step down centre tapped transformer to step
down the mains voltages.
 Four 1N4001 diodes are used for rectification of the AC voltage to DC.
 470µF electrolytic capacitors are used to filter the voltage coming from the diodes and
47µF capacitors are used for decoupling.

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Audio Amplifier
 The LM386 is an integrated circuit containing a low
voltage audio power amplifier.
 It is suitable for battery-powered devices such as radios,
guitar amplifiers, and hobby electronics projects.
 The IC consists of an 8 pin dual in-line package (DIP-8)
and can output 0.25 to 1 watts of power depending on the
model using a 9-volt power supply.
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Audio Amplifier
• To make the LM386 a more versatile amplifier, two pins (1 and 8) are provided for gain
control. If a resistor is placed in series with a capacitor, the gain can be set to any value from
20 to 200.
o Capacitance used: 10µF
o Resistance used: 5kΩ (pre-set)
• Pins 2 and 4 are grounded.
• Input signal is fed through pin 3 via 10kΩ pre-set resistor, which is used as volume controller.

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• A 220µF electrolytic capacitor is used with pin 5 (output pin) to remove the dc components of
the output signal. A filter circuit is provided with 10Ω resistor in series with 47nF ceramic
capacitor to remove high frequency noises.
• Power is supplied through pin 6. A 10µF capacitor is connected in parallel with a 0.1µF
capacitor. These two capacitors act as decoupling capacitors.
• Pin 7 is bypass, which can be left open or connected to the ground through a capacitor for
stability.
Audio Amplifier

9. IIEST, SHIBPUR
Burglar Alarm and Counter
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IC 7486 IC 4033

10. IIEST, SHIBPUR 10
Burglar Alarm and Counter

11. IIEST, SHIBPUR
Alarm system circuit:
• The value of resistance of L.D.R changes
according to the intensity of light. So, the
voltage drop across it also changes when
connected across the source.
• The value of the fixed resistance is so
chosen that when connected with that
L.D.R. & the 5V dc supply, the voltage drop
across it will be almost 4.9-4.8V and 0.1-
0.2V in light and dark respectively.
• One of the inputs to the XOR gate is the
voltage between L.D.R. and the fixed
resistance, while the other is at logic HIGH
(almost 4.9V). The output of the XOR gate
is fed to a buzzer, which makes sound when
a burglar passes before the L.D.R.
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Burglar Alarm and Counter
To the Counter Circuit

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Counter Circuit:
• This circuit involves a 4033 IC, which
is a 4-bit Johnson counter as well as a
Binary to Decimal decoder, and a
common cathode based 7-segment
L.E.D.
• The connection between 4033 IC and
the 7-segment L.E.D is made as per the
corresponding datasheets.
• The output of the XOR gate of the
alarm circuit is used as the clock pulse
for the 4033 IC. In this way, this circuit
records the number of burglars passing
past the system.
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Burglar Alarm and Counter
From the Alarm Circuit

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Fire Alarm
Resistor: 330kΩ, 100Ω Capacitor: 0.04 µF
Transistor: BC-369 (p-n-p), BC-548 (n-p-n) Buzzer: Works for 3-27 V supply
Fire Switch Bulb Battery: 9V

14. IIEST, SHIBPUR
Fire Alarm
Fire Switch Bulb:
The fire switch bulb consists of two plates as
shown in the picture. Initially when connected to
any circuit, the switch is open as there is no
connection between the two plates. Now the
black solid material is sensitive to heat and if a
source of fire is held near the tip of the head, the
solid expands in such a way that the plate gets
connected to the metal rod, thereby completing
the circuit. Now if the fire is removed, then with
time the solid again contracts and the circuit is
again opened.
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Condenser Mic
Clap Switch

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Clap Switch
Internal Circuit of 555 IC

17. IIEST, SHIBPUR
Clap Switch
On producing sound near condenser mic, this sound will be converted into electrical energy
and it will raise the potential at the Base, which will turn the Transistor ON. The potential at
Point A would become low and it will trigger the 555 IC because of the low voltage (below
Vcc/3) and LED will turn ON.
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Initially the transistor is in OFF
state because there is not enough
(0.7V) base-emitter voltage to
turn it ON. Point A is at high
potential; as a result, Trigger pin
2 is also at high potential. As we
know that, to trigger the 555 IC
through Trigger PIN 2, the
voltage of the PIN 2 must be
below Vcc/3. So at this stage,
LED is OFF.

18. IIEST, SHIBPUR
After some time, LED will be
turned OFF automatically
because we are using 555 timer
IC in Monostable Mode. LED
will remain turned ON for
1.1*R1*C1 seconds. This
duration can be changed by
changing the value of Resistor R1
or/and Capacitor C1. Control PIN
5 of 555 Timer IC should be
connected to Ground through a
0.01uF capacitor.
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Clap Switch

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