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Project Title

Here is a teleremote circuit which enables switching ‘on’ and ‘off’ of

appliances through telephone lines. It can be used to switch appliances

from any distance, overcoming the limited range of infrared and radio

remote controls.

The circuit can be used to switch up to nine appliances (corresponding

to the digits 1 through 9 of the telephone key-pad). The DTMF signals

on telephone instrument are used as control signals.

The digit ‘0’ in DTMF mode is used to toggle between the appliance

mode and normal telephone operation mode. Thus the telephone can be

used to switch on or switch off the appliances also while being used for

normal conversation

ABSTRACT

PROJECT BLOCK DIAGRAM

HARDWARE REQUIREMENTS

POWER SUPPLY BLOCK

555 TIMER

RELAY

MT8870 DTMF DECODER

CD4049 INVERTER

CD4013 FLIP FLOP

MCT2E OPTO-ISOLATOR

74LS154

BC547

NPN TRANSISTOR

POWER SUPPLY

230 V AC 50 Hz

5V DC

12V step down transformer

Filter(470µf)

5v RegulatorBridge rectifier

555 TIMERThe 555 Timer IC is an integrated circuit (chip) implementing a variety of timer and multivibrator applications

The 555 has three operating modes:

• Monostable mode: in this mode, the 555 functions as a "one-

shot". Applications include timers, missing pulse detection,

switches, touch switches, frequency divider, capacitance

measurement, pulse-width modulation (PWM) etc.

• Astable - free running mode: the 555 can operate as an

oscillator. Uses include LED and lamp flashers, pulse

generation, logic clocks, tone generation, security alarms,

pulse position modulation, etc.

• Bistable mode or Schmitt trigger: the 555 can operate as a

flip-flop, if the DIS pin is not connected and no capacitor is

used. Uses include bounce free latched switches, etc.

Pin Name Purpose

1 GND Ground, low level (0 V)

2 TRIG OUT rises, and interval starts, when this input falls below 1/3 VCC.

3 OUT This output is driven to +VCC or GND.

4 RESET A timing interval may be interrupted by driving this input to GND.

5 CTRL "Control" access to the internal voltage divider (by default, 2/3 VCC).

6 THR The interval ends when the voltage at THR is greater than at CTRL.

7 DIS Open collector output; may discharge a capacitor between intervals.

8 V+, VCC Positive supply voltage is usually between 3 and 15 V.

Internal architecture of 555 timer

CD4049-INVERTER

The CD4049 devices are inverting hex buffers, and feature logic

level conversion using only one supply voltage (VCC)

These devices are intended for use as CMOS to DTL/TTL

converters and can drive directly two DTL/TTL loads

Pin out

FEATURES

CD4049UB Inverting

High Sink Current for Driving 2 TTL Loads

High-To-Low Level Logic Conversion

100% Tested for Quiescent Current at 20V

Maximum Input Current of 1μA at 18V Over

Full Package

Temperature Range; 100nA at 18V and 25oC

5V, 10V and 15V Parametric Ratings

FUNCTIONAL DIAGRAM

DTMF DECODER

This circuit detects the dial tone from a telephone line and decodes

the keypad pressed on the remote telephone.

Two distinct frequency tones make up the DTMF(dual tome

multiple frequency), and hence the name.

The dialer and the telephone exchange communicate one way

through the DTMF communication.

The tone generator and the tone decoder consist of a complete

communication setup. In this project, IC MT8870DE is used to decode the input dial tone

to the dialed numbers.

CONTD..

These digital bits are interfaced to a microcontroller for any

application.

Pulse/dial tone method is used in the modern telephone

communication.

There is a dial tone generator on the caller side and a unique tone

consisting of two audible tone frequency is generated when the

user presses a button.

As an example, 697hz & 1209hz will be generated when key '1' is

being pressed on the phone.

A decoder circuit is present on the receiver side, which decodes the

tone to a digital code.

CD4013 FLIP FLOP

The CD4013B dual D-type flip-flop is a monolithic complementary MOS

(CMOS) integrated circuit has two D-type flip-flops, which you can use

independently

A D-type flip-flop, also called a D-type bistable, is a subsystem with two stable

states. Using appropriate input signals, you can trigger the flip-flop from one

state to the other.

Features: 

High-Voltage Type (20V Rating) with Set-Reset Capability

Static Flip-Flop Operation

Medium-Speed Operation - 16 MHz (typ.) Clock Toggle

Rate at 10V

Maximum Input Current of 1μA at 18V Over Full Package

Temperature Range; 100nA at 18V and +25oC

The D-type has four inputs. These are:

Data input: This is connected either to a LOW voltage,

logic 0, or to a HIGH voltage, logic 1

Clock :The clock input is rising-edge triggered, meaning

that it responds only to a sudden change from low to high.

Set input: The SET input is normally held LOW. When it

is pulsed HIGH, the outputs of the bistable are forced

immediately to the SET state.

Reset input: The RESET input is normally held LOW.

When it is pulsed HIGH, the outputs of the bistable are

forced immediately to the RESET state.

Continued ….

Fig:Functional Diagram

OPTO-ISOLATOR

Opto coupler is a 6 pin IC.

It is a combination of 1 LED and a transistor.

when light falls on the Base-Emitter junction then it

switches pin5 goes to zero.

When logic zero is given as input then the light doesn’t

fall on transistor so it doesn’t conduct which gives logic

zero as output.

When logic 1 is given as input then light falls on

transistor so that it conducts, that makes transistor

switched ON and it forms short circuit this makes the

output is logic zero as collector of transistor is

connected to ground.

74LS154

Each of these 4-line-to-16-line decoders utilizes TTL

circuitry to decode four binary-coded inputs into one of

sixteen mutually exclusive outputs when both the strobe

inputs, G1 and G2, are LOW

The demultiplexing function is performed by using the 4

input lines to address the output line, passing data from

one of the strobe inputs with the other strobe input

LOW. When either strobe input is HIGH, all outputs

are HIGH.

These demultiplexers are ideally suited for

implementing high-performance memory decoders. All

inputs are buffered and input clamping diodes are

provided to minimize transmission-line effects and

thereby simplify system design.

FEATURES:

Decodes 4 binary-coded inputs into one of 16 mutually exclusive

outputs

Performs the demultiplexing function by distributing data from one

input line to any one of 16 outputs

Input clamping diodes simplify system design

High fan-out, low-impedance, totem-pole outputs

Typical propagation delay

3 levels of logic - 23 ns

Strobe - 19 ns

Typical power dissipation 45 Mw

BC547

The BC547 transistor is an NPN Epitaxial

Silicon Transistor.

The BC547 transistor is a general-purpose

transistor in small plastic packages.

It is used in general-purpose switching and

amplification BC847/BC547 series 45 V, 100

mA NPN general-purpose transistors.

Whenever base is high, then current starts

flowing through base and emitter and after

that only current will pass from collector to

emitter 

BIBILOGRAPHY

www.beyondlogic.org

www.wikipedia.org

www.howstuffworks.com

www.alldatasheets.com

QUERIES ?

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