Download telephone-intrusion-notification-system

1
Telephone Intrusion Notification System
Lekshmi. III SEM EC, LBS College of Engineering, Trivandrum
Power supply
D1 IN 4007
1
P
7812
230 V AC
3
2
100 R
N
12-0-12 V
D2 IN 4007
500 mA
Transformer
+
C1
2200 uF
25 V
Power
ON
12 V DC
LED
Yellow
Powe Supply
12 Volt 500 mA Common
Ground
Power supply to the circuit is derived from a 12-0-12 500 mA step-down transformer. The low voltage AC is rectified by IN 4007 diodes
and made Ripple free by 2200 uF capacitor. IC 7812 is used to give 12 volt regulated power to the circuit.
Light Sensor
LDR (Light Dependent Resistor) is used as the light sensor for the automatic operation of the circuit at sunset. LDR has low resistance
about 100 ohms when it is illuminated by the day light and it remains conducting. The resistance of LDR increases to 1 Meg ohm or
more in darkness and becomes non conducting. LDR is used to give a high voltage at the reset pin 12 of IC1 (CD 4060) to prevent its
oscillation. IC1 oscillates only when its pin 12 becomes low at sunset as the LDR cease conducting. This enables the IC1. In the morning,
when light falls on the LDR it conducts and disables IC1. Preset VR1 adjusts the sensitivity of LDR to the particular light level.
2
Long duration Timer
CD 4060(IC1) is used as a long duration timer to activate the remaining part of the circuit after 4 hours around 10 pm.
The timer circuit is designed using the 14 stage ripple counter IC CD 4060 to give 4 hours timing by taking pin 2 as output. When the
reset pin12 of IC1 becomes low at sunset, it starts oscillation. Resistor R3 along with VR2 and capacitor C1 maintains the oscillation of
IC1 as indicated by the blinking of LED 1(Green LED) connected to its output pin 7(Q3).The timeout period of the timer can be
calculated using the formula
t = 2 n / f osc = in seconds.
‘n’ is the selected Q output
f osc = 1 / 2.5 (R1.C1) R1 is the resistor in ohms connected to the pin 10 and C1 is the capacitor in farads connected to the pin 9 of IC1.
When the pin 2 becomes high diode IN 4148 forward biases and inhibits further oscillation of IC1 and pin 2 output remains high till IC1
resets in the morning.
When the output pin2 of IC1 becomes high, Transistor T1 (BC 547) conducts and provides power to IC2 (CD 4060) and reed switch.
Reed switch is used as a door switch to activate the circuit when the door is opened. It is a normally open type (NO) so that it opens
when there is no magnet is placed close to it. In the arrangement, a magnet is fixed to the door and the reed switch to the frame. So
when the door is closed, magnet will pull the contacts of the reed switch so as to make it conducting. Reset pin 12 of IC2 gets a high
voltage through the reed switch and IC2 remains standby.
CD 4060 (IC2) is used as a short duration timer with 1 minute ON/OFF cycles by taking pin 13 output. Capacitor C2 and resistor R8
gives the one minute time cycled from output pin 13.
When the door is opened, reed switch and magnet separates and the contacts of reed switch opens. At this time, pin12 of IC2 goes low
and it starts oscillating. After one minutes its pin 13 becomes high to trigger relay driving transistors T2, and T3.
Two relays are used to control the telephone and tape recorder. Relay 1 is DPDT (Double Pole Double Throw) is used to connect the off
hook switch and redial switch of telephone. When Relay 1 energize, its NC contacts breaks so that the phone will be in the OFF Hook
state. At the same time its NO contacts connects the redial switch. In short, relay 1 makes the telephone similar to a person taking the
receiver and pressing the redial switch to make a call.
Relay 2 is SPDT type (Single Pole Double Throw). When it energize, its NO contacts gives power to the tape recorder. In short, when
both relay 1 and 2 energize, tape recorder plays the recorded message and telephone dials the number.
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Telephone interface
C1
0.01
100V POLY
Telephone Lines
R1
10K
A
Bridge
IN 4007 x 4
ZD 12 V 1W
R2
22K
Tape
Head phone
Socket
B
Recorded message comes from the tape recorder is given to the interface circuit from the head phone socket of the tape recorder using a
jack.
The voice signals passes through R1, R2 and C1 to the bridge rectifier to the telephone line. Since the telephone line has 48 volts DC in
the ON Hook state (reduces to 12 volts in OFF hook state) 12 V Zener diode is used to protect the interface circuit.
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LDR
Q12 R11K
S1
IN4148
IN 4007
IC1
CD 11
4060
10
12
12
R3 100K
12
Relay
6V 100R
C
Reed
Switch
NC
7
12
C1 0.22
Reset
R4
470R
C
C
C2 0.22
16
D1
IN
4007
D2
IN
4007
RL1
9
9
8
SPDT
Relay
6V 100R
DPDT
R2 1M
VR2 100K Pot
IN 4007
0
T1
BC 547
2
Magnet
16
10
IC2
CD
11
4060
NO NC NC NO
R7 100K
RL2
NO
NC
R8 1M
T3
VR1
100K
1000
UF
25V
13
LED1
Green
Active
R9 100R
R5
12K
R6
150 R
T4
BC 547
8
Trigger
Long duration
When door opens,
Timer
reed switch opens.Reset pin 12 of
Detect light intensity
IC2 goes low and IC2 starts Oscillation
and activates timer
Timer starts oscillations
around 6 pm
as indicated by flashingGreen LED.
Output pin 2 becomes high after 4 hours
around 10 pm. Gives power to the Alarm
generator through T1.IC1 stops oscillation and
output 2 remains high till morning and then
resets
Light Sensor
BC 547
R10 100R
6V PCB Relay
Relay Driver
Relay Driver
When pin 13 of IC2
becomeshigh, T3 and T4 conducts
to operate relays 1and 2 .Hook of
telephone is connected to
the NC contactsand redial
switch to NO contacts
of the DPDT relay 1. Relay 2 makes
contact and give power supply to the
Tape Recorder which sends the voice
message to telephone lines
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Front View
TIP
122
B
C
BC
547
E C
B
E