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Data Communication Using Power Line- voice and data






Data commmuniction using power line is important project according to today’s increasing rush of power line and data lines. In this project we will transmit data using earth wire. Earthing very important  for this project. It will also help to control the the various devices with power supply circuit.    In this project we  will transmit data using DTMF encoder IC  91214 . IC 91214 is frequency generators . actually we will send particular frequency to decode it at reciver. We wll amplify the signal after DTMF technology play the key role .In amplifiers first of all we will use voltage amplifier and then power amplifier . there will be IC741 as voltage amplifier circuit. And then transistorized  power amplifier circuit. In receiver side there will be amplifiers then there will be DTMF decoder driver IC 8870. we will reamplify the signal because of the week signal detected  at receiver. Ic 8870 has pin no2, 3 as input pins . output of decoder will be Binary coded decimal. There will be four outputs will be input to Microcontroller IC 89c051 . output of IC will be on LCD display. In this way we will transmit data . DTMF frequency lie with in voice frequency range.

 DTMF is Dual  tone Multi frequency. Dtmf frequency wave is very equal to sine wave like



In spite of sending pulses we  will send DTMF signal. This technology is use in telephones. That’s why its very important and reliable in Data communication. Morever its frequency range lie with in voice frequency range.






1.                 DTMF DECODER

In dtmf decoder circuit we use ic 8870 ic. IC 8870 is a dtmf decoder ic. IC 8870  converts the dual tones to corresponding binary outputs.


DTMF SIGNALLING. Ac register signaling is used in dtmf telephones, here tones rather than make/break pulse are used fro dialing, each dialed digit is uniquely represented by a pair of sine waves tones. These tones ( one from low group for row and another from high group fro column) are sent to the exchange when a digit is dialed by pushing the key, these tone lies within the speech band of 300 to 3400 hz, and are chosen so as to minimize the possibility of any valid frequency pair existing in normal speech simultaneously. Actually, this minimisator is made possible by forming pairs with one tone from the higher group and the other from the lower of frequencies. A valid dtmf signal is the sum of two tones, one from a lower  group ( 697-940 Hz) and the other from a a higher group ( 1209-1663 Hz). Each group contains four individual tones.  This scheme allows 10 unique combinations. Ten of these code represent digits 1  through 9 and 0. . tones in DTMF dialing  are so chose that none of the tones is harmonic of  are other tone. Therefore  is no change of distortion caused by harmonics. Each tone is sent as along as the key remains pressed. The dtmf signal contains only one component from each  of the high and low group. This significaly simplifies decoding because the composite dtmf signal may be separated with band pass filters into single frequency components, each of which may be handled individually.

First ic of this section is ic 74154. IC 74154 is  bcd to decimal decoder. 74154 is active low ic. Pin no 20,21,22,23 is connected to dtmf decoder ic.

Pin no 18 and 19 of this ic is connected to the collector of one npn transistor Base of the npn transistor is connected to the pin no 15 of the ic 8870. When dtmf decoder decode the signal at that time pin no 15 is on for a time and acknowledge the signal. This signal is fed to the  base of NPN transistor through 1 kohm resistor. When this signal is coming then 74154 is on and gives a output.


Then output of 74154 is active low. We will use IC 74ls 74  or transistors to invert the active low output. After that we will use flip flop & SCRs or relays to control & to give 220v Ac to devices for switching purposes.





Components required:-


Ic 741 Op Amp

IC 7805 Voltage Regulator

Diode 4004 Pn diodes

IC 91214 DTMF encoder

IC 7447- Seven Segment Display driver IC

Seven Segment Dispaly

Ic8870  DTMF decoder

9 v Transformer 50mA

Optical fiber Singal mode

Resistances- 10k,1k,4.7k,220k

Capacitors- 0.1microfarad,00.1 microfarad,1000µf,470µf

Cupper clad board

Fecl3 for PCB design



Hardware required-


8051 programmer universal kit


CRO 20 Mhz


Digital multimeter


Software Required:-