Power line communication using an audio input
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Power Line Communication using an Audio Input. ECE 445 Group 8 TA: Tony Mangognia Team: Sam Tsu, Marshall Katz, Rajat Singhal. AGENDA. Introduction. ‘Wireless’ sound transmission using AC power lines. Audio in through a standard device such as an Ipod.

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Power line communication using an audio input

Power Line Communication using an Audio Input

ECE 445 Group 8

TA: Tony Mangognia

Team: Sam Tsu, Marshall Katz, Rajat Singhal


Agenda

AGENDA


Introduction

Introduction

  • ‘Wireless’ sound transmission using AC power lines.

    • Audio in through a standard device such as an Ipod.

    • Transmit the signal at the sending end through the AC power line.

    • Receive the signal at the receiving end and filter out the noise

    • Audio out through a standard speaker system.


A detailed look

A Detailed Look…

  • Interference from AC lines which operate at 60 Hz - 120 V.

  • FM modulation necessary to transmit at higher frequencies.

MODULATION

DEMODULATION

  • Demodulation circuit required to demodulate the modulated signal and convert to standard audio output.

Filter circuits required to block 60Hz noise and any frequencies not part of the transmitted audio.


Features

Features

  • Commercialization idea behind the project based on the fact that the signal is not being broadcasted through the air.

    • Security Issues

    • Intercom Systems

    • PA systems

  • Other advantages

    • Relatively inexpensive setup

    • Neat System

    • Increased efficiency


Design overview

Design Overview


Modulation circuit

Modulation Circuit


Modulation circuit continued

Modulation Circuit Continued…

  • The VCO used for modulation purposes was the LM565

  • The frequency production of the VCO was controlled using:

    where Rt = Timing Resistance on pin 8

    Ct = Timing Capacitance on 9

    Vcc = Power Supply Voltage

    Vc = The control voltage on Pin 7


Demodulation circuit

Demodulation Circuit


Demodulation circuit continued

Demodulation Circuit Continued..

  • LM565 used to implement the VCO

  • The input signal coupled in to the circuit through pin 2

  • A more complicated network of components at output for noise reduction purposes.

  • Potentiometer used to match current frequency to the carrier frequency.


Filters

Filters

  • Noise above 10Khz was minimal

  • Standard HPF implemented.

Chosen values were R = 15kΩ and C = 1nF


Component selection

Component Selection

  • LM 565

    • Readily available

    • Carrier frequency adjustment through timing capacitor and resistor

  • High Voltage Capacitors

    • 250 Volts DC / 180 Volts AC

  • Potentiometers

    • Easy tuning manipulation

  • Fuses

    • .125 mA / 120 Volts AC


Design and testing methodology

Design and Testing Methodology

  • Down-up approach

    • Protoboard to PCB

    • Individual components to integrated system

    • Progressive stages of building and testing


Design and testing methodology1

Design and Testing Methodology

1) Build Modulator/Demodulator

2) Test Modulator/Demodulator Functionality

3) Build Filters

4) Test Filter Functionality

5) Combine Modulator/Demodulator with Filter

6) Test Transmitter/Receiver Functionality

7) Combine Transmitter/Receiver with 60 Hz Simulated Noise

8) Test with Simulated Noise

9) Combine Transmitter/Receiver with 60 Hz Power Line

10) Test with Power Line (Variac)


Board layout transmitter

Board Layout - Transmitter

1) Audio Input

4) Filter Stage

(DC Power Input)

15 Volts

.023 Amps

.345 Watts

5) To Power Line

3) FM Modulation

2) Carrier Tuning


Board layout receiver

Board Layout - Receiver

3) Receiver Tuning

(DC Power Input)

4) Demodulation

15 Volts

.012 Amps

.18 Watts

5) Audio Out

1) From Power Line

2) Filter Stage


Modulator testing

Modulator Testing

Computer

Audio Signal

Modulator

100 kHz FM Modulated Signal


Power line communication using an audio input

Timing Capacitor (pin 9):

~100 kHz

Modulator output :


Demodulator testing

Demodulator Testing

DC Power

Demodulator

(No signal)


Power line communication using an audio input

Timing Capacitor (pin 9):


Filter testing

Filter Testing

Filter

Input Signal

60 Hz

100kHz

Output Signal


Power line communication using an audio input

60 Hz Response:

Gain = .01 V/V

100 kHz Response:

Gain = .98 V/V


Integration testing

Integration Testing

Speaker

Computer

Demodulator

Power Strip

Modulator

(Filter)

(Filter)


Power line communication using an audio input

Qualitative Evaluation

-Clarity of signal (after tuning)

Quantitative Evaluation

- SNR (at 10 kHz)

- 29.06 dB


Communication with simulated 60hz

Communication with simulated 60Hz

Speaker

Simulator

60 Hz, 20 volts

Computer

Demodulator

Power Strip

Modulator


Power line communication using an audio input

Qualitative Evaluation

-Clarity of signal (after addition tuning)

Quantitative Evaluation

- SNR (at 10 kHz)

- 17.19 dB


Communication over power line

Communication over Power Line

Speaker

Power Line

60 Hz, 120 volts

Computer

Demodulator

Power Strip

Modulator


Challenges filter performance

Challenges - Filter Performance

  • Relative background noise persistent through the initial filter design.

    • DC offset distortion of the output signal

      • DC offset connected to ground through inductors causing over current conditions.

  • Proposed three stage RC filter design


Filter performance

Filter Performance


Challenges power line connections

Challenges - Power Line Connections

PROBLEMS

SOLUTIONS

  • Use a 1:1 transformer to isolate circuits from power line and each other

  • A 10:1 transformer rated at 120V with ferrite core used to step down the voltage requirement in the circuit

  • Filter performance distorted at ratings of 120V

  • Ground issues

Coupling the circuits together through the power line presented several sources of difficulties and errors.


Challenges power line connections1

Challenges - Power Line Connections

1:1 Transformer Frequency Response at 60Hz, 100kHz


Challenges power line connections2

Challenges - Power Line Connections

PROBLEMS

SOLUTIONS

  • 10:1 transformer needed to be a high wire resistance and a ferrite core

  • Commercial production was limited

  • Transformer has resistance of 0.1Ω

    and reactivity of 0.3μH

  • Winding of a ‘home made’ transformer – However, number of turns required was excessive


Challenges power line connections3

Challenges - Power Line Connections

  • Unavailability of high rated transformer promoted the use of a variable transformer – Variac

    • Physically transmit audio signal at the rated voltage of the home made transformer

  • Relative grounding issues resulted in short circuit and damage to the PCB.


Final working design

Final ‘Working’ Design

  • New design connection - filter preceding transformer

    • Filter before transformer to reduce voltage across transformer

  • Dual capacitors to allow either input to be active wire


Future

Future

Stereo Implementation

Two separate transmitters and receivers operating at 100KHz and 200KHz to enable stereo sound

Audio Output Amplifier

Amplification of output signal to have volume control, especially for commercial systems.


Power line communication using an audio input

QUESTIONS/FEEDBACK


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