Auto Answering with Security dialup

Project code:- E25 Project Cost:- INR:- Rs. 8500/- USD:- 230$

Auto Answering with Security dialup

The said project is an enhancement of commercially available auto answering machine., not only answers the pre-recorded incomming call,but also safe guards your house/office against inturders. A Strong infra red transmitted beam goard your house against any inturder.

Auto Answering with Security dialup Block Diagram Auto Answering with Security dialup Block Diagram

In case this beam is intrupted by any inturder, it will make an emergency call and will deliver an emergency message . Similiarly other types of sensors could be connected as well. For the security of your house/office/property.

This project is based on the world,s most popular microcontroller 8051. we have used ATAMEL 89C51(IC1) which belong to the same family.IC2 Apr9600 is a re-recordable speech ic where all the messages are recorded. Ic4 LM 386 is an amplifire ic for amplification of sound produced by sound amplifier.

The entire circuit is powered by 5v dc power supply which comprises of: IN4007 D1-D4 diodes ,forms a bridge rectifire circuit .Capacitor C1 and C2 are filter capacitorc and IC5 LM7805 is a Regulator IC which gives DC5V regulatedout put. LD1 is a power indication led Since LED’S are rated for 3.5v so we have to connect R1 in order to drop excessive voltage and limit the current.

CN1 is a connector where we connect the 9Volt one amp power transformer.Capacitor C9,C10 and C18 are noise filters in the power supply.

CIRCUIT DESCRIPTION:
Answer mode
CN3 is connected with telephone line. D5-D7 forms bridge rectifire ciruit when ever any in-comming call comes, ringing signal which is around 55v ac ,passes through C6 and R3 filtered through C7 ,R4and limited by D9 zener diode. Rectified voltage drives an opto-coupler IC3-MCT2E through R5. with the ringing signal collector of the MCT2E will become low and is connected to P3.7 of micro-controller.
Microcontroller will count for eight rings through pin number P3.7.and will switch ON off hook relay. RELAY RL1 which is driven by transister Q3 and Q4,and by pin P3.5 of 80C51 through current limiting resistance R8.. With this RELAY RL1 comes ON ,resistance R9and capacitor C8 comes parallel into the telephone circuit , and telephone line voltage is dropped to 11v or 12volts dc. This condition is known as OFFHOOK condition, which is similar to lifting an telephone Handset. With this telephone exchange understands that person has lifted the hand set, and ring signal is stopped and communication begins ..Meanwhile pin 1 of IC2 APR 9600 get trigger pulse from microcontroller P1.2 and prerecorded answer message is played back through pin 14 and 15 of APR 9600 and is connected to audio amplifire IC4 LM 386 ,through R20 , R21 and C16,C17 to pin 2 and 3 .Amplified out put is available at pin no 5 of IC4 which is connected to speaker as well as secondary of TR1 an isolation transformer connected across telephone line. D12 and d13 zener diodes connected back to back maintains the Impedence of the transformer. OFFHOOK relay will get switched off after a gap of 25-30 seconds after the answering.

Period is over.

Record mode To record the message , shift the record play switch to record mode, and press SW1 switch , a beep will be heard ,after this beep speek your message at mic by keeping the record switch pressed and when message is over, release the record switch and change the record play switch to play mode.
Recorded message can be played back and tested by pressing the SW1 switch. Continue press of this switch will play this message continuesly.
Similarly SW2 is used to record the emergency message.

Emergency Dial Mode : Sensors can be connected to CONECTOR IN1 IN2 & IN3 .These connections Ultimately connected to P1.6,P1.7 and P3.4 of Microcontroller. .Normal state of these pins is always at high logic. When ever any of these pins detects LOW LOGIC from any of the sensor, the micro-controller will first switch ON RL1 OFFHOOK relay. This is equivalent to lifting if hand set and a DIAL RELAY K2 will dial out the number by making and breaking its contact is similar to sending pulses through normal telephone line say if number 9 is to be dialed it will make break contact 9 times. This relay is driven through P3.6 pin of 89C51 and transister Q1 ,Q2, and R6. PIN 2 of APR9600 will get triggered and an EMERGENCY message will be played . Same message is coupled to the telephone line which has been explained in autoanswer mode. whenever anys ensor get triggered. the emergency message is played This message will be repeatedly send after and sent across the

This message will be repeted after a interval of one minute untill a person comes and reset the device. P1.2 and P1.3. are responsible to trigger emergency message.

R6 and R8 connected to the base of transister Q2 and Q4 are voltage dropping resistors. Transistors Q1 & Q2 drives the DIAL relay K2, and Q3,Q4 drives the OFFHOOK relay.
Logic high on the base of these transistors would keep the RELAYS OFF and low logic will make the RELAYS to ON condition

Crystal X1 along with C4 and C5 gives the necessary clock to microcontroller.
Capacitor C3and R2 gives the required reset pulse to microcontroller.RST SW is master reset switch.
Resistances connected to indication leds LD1 is current limiting resistors

Dialing Operation : Relay RL2 is a dial relay it,s contacts are in series with the telephone line. Contact make break is the principle of dialing , as it was used in olden days with round dial type telephone hand sets., if you want to dial ‘5’ just break the contacts 5 times. To dial
‘9’ break the contact 9 time. Similarly for all the numbers, to dial ‘0’,you will have to break the contact ten times. This type of dialing is known as pulse dialing.
By making breaking the contacts we send the series of pulses to exchange, there should be at least one second gap between two numbers.

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