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ABSTRACT 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

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 Bridge rectifier 5v Regulator 230 V AC 50 Hz 5V DC Filter(470µf) 12V step down transformer

555 TIMER The 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.

Internal architecture of 555 timer 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.

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

High Sink Current for Driving 2 TTL Loads 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: Continued …. 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. 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

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