BLUETOOTH CONTROLLED HIGH

POWER AUDIO AMPLIFIER

PRESENTED BY:

BIJAY RAJ PAUDEL (ROLL NO: 067/BEX/105)

SAGAR MALI (ROLL NO: 067/BEX/133)

SUJAN SHRESTHA (ROLL NO: 067/BEX/140)

Thapathali CampusFinal Presentation

2013

INTRODUCTION

•Decent quality High Power Audio Amplifier

• 8051 Microcontroller based control

•Digital control over tone, effects & volume

•Wireless Bluetooth Interface

•Control via Computer Software/ Android software and/or Keypad

OBJECTIVES

• To construct cost effective high power audio amplifier.

• To implement 8051 μc along with it’s interfacing.

• To control the system via wireless Bluetooth module.

• To program μc & develop GUI based PC application.

• To improve our programming & practical skills.

PROJECT IN BLOCK DIAGRAM

MAIN BOARD Audio

Input

PROJECT IN BLOCK DIAGRAM

CONTROLLING UNIT

BRIEF EXPLANATION OF EACH BLOCK

BLOCK REPRESENTAI

ON OF

POWER SUPPLY

1.POWER SUPPLY

1.1. RECTIFIER

• 6A capacity bridge rectifier with +43 and -43 volt output

• With Electrolytic and Ceramic capacitor filer

• 5A fuse for protection

BRIEF EXPLANATION OF EACH BLOCK

1.2. VOLTAGE REGULATOR

• Based on LM337

(negative voltage regulator)

and LM137

(positive voltage regulator)

• Conduction through

Power transistors for increased

current capacity.

BRIEF EXPLANATION OF EACH BLOCK

2. PRE AMPLIFIER

• 3 active filters( for bass, mid, treble)

• 2 op-amp amplifiers first before filter

& next after filter for larger gain.

• Variable Gain controller

• In-built Distortion effect

(achieved by diode clipping)

BRIEF EXPLANATION OF EACH BLOCK

3. DIGITAL VOLUME & TONE CONTROL

• Based on analogue multiplexers. (8x1 for bass, mid, treble and 16x1 for volume control)

BRIEF EXPLANATION OF EACH BLOCK

4. POWER AMPLIFIER

• Simulated for 80Watt output in Proteus, (power supply of +-30 V)

• 3 stage amplifier-Differential amplifier input (for gain)

Voltage amplifier

Power amplifier

• Output short circuit protection

BRIEF EXPLANATION OF EACH BLOCK

5. Bluetooth Module

•Uses class C Bluetooth radio

•Uses SPP (Serial Port Protocol) for interface

•4 pins for Vcc, Gnd, Txd and RxD

•Works at default baud rate of 9600 bauds

•Interface with 8051 microcontroller using UART

•Works at CMOS voltage level (3.3V, 0V)

BRIEF EXPLANATION OF EACH BLOCK

6. TTL – CMOS level Converter

•Bluetooth works on CMOS level and microcontroller on TTL level so voltage level conversion is required.

•Achieved by using N-Channel Enhancement mode MOSFET

•Bidirectional operation (3.3V to 5V and 5V to 3.3V)

•Two similar circuits for TxD and RxD

BRIEF EXPLANATION OF EACH BLOCK

COMPUTER GUI

• Codes in C# .NET

• Uses serial port class provided by .NET library

• User interface in WPF

4. Main Controller Board

•8051 microcontroller based

•Interface with LCD in 8 bit mode

•Interface with EEPROM

•Interface with three 8x1 analogue multiplexers for bass, mid, and treble control and one 16x1 multiplexer for volume control

•Interface with Bluetooth module

BRIEF EXPLANATION OF EACH BLOCK

ALGORITHM FOR MAIN CONTROLLER

START

Initialize LCD

Show Welcome bass, mid, Volume & treble status

Initialize Serial Port in mode1 and Set Timer 1 for 9600 baud in mode 2

Set Timer 0 value and enable timer 0 interrupt

Enable timer 0 and timer 1

While (1)

Check interru

ptUpdate LCD with Bass, mid, treble

and volume’s current value

SITimer 0 Interrupt

Serial Interrupt

C

Check Keypad Pins

Send updated values to serial port(SBUF)

Send data corresponding pins

attached to multiplexers

C

Increase/Decrease volume, bass, mid and

treble

SI

Is TI set?

Is RI set?

Read SBUF serial portRI ≠0

Update Vol, Bass, Mid Treble value as command received

in SBUFSend data to

corresponding pins attached to multiplexers

YesTI=0

No

Yes

RI=0No

4. KEYPAD

• 4*4 matrix keypad.

• 16 keys produce 16 different combinations to interface with the

main controller

• Extra interrupt signal pin

• Backlight LEDs for low light operation

BRIEF EXPLANATION OF EACH BLOCK

5. KEYPAD CONTROLLER

• Separate Controller to scan keys to relieve main controller of input reading duties

• 8051 microcontroller based

• Accepts the input from keypad

• Outputs information to microcontroller

at main board

BRIEF EXPLANATION OF EACH BLOCK

ALGORITHM FOR KEYPAD CONTROLLER

START

Initialize all ports to zero

Is key presse

d?

Initialize all rows to 1

Initialize C1=0 other to 1

Is R1=0?

Output 0 to port 1

Similar to other rows R2 to R4

Initialize C2 =0 & other to 1

Is R1=0?

Output 5 to port 1

Similar to other columns & rows

Yes

PROBLEMS

• Overheating of power transistors

• Noise induction in preamplifier.

• Speaker over voltage spikes damaging the speaker under high volumes

• Digital potentiometer not available

SOLUTIONS

• Using transistors in metal cases and larger heat sinks

• Proper shielding of preamplifier and connecting wires

• Use of filter output capacitor and output audio transformer(yet to be implemented

• Use of analogue mux, with lesser resolution but it does the job

• Auditorium Hall

Seminar

Presentation

Lecture

• Theatrical and Concert sound

reinforcement

• Home Theater System

• Car Audio System

• Guitar Amplification

APPLICATIONS

• Limited effect is only implemented because of unavailability of effect IC and complex design if done using discrete components.

• Separate independent remote control with LCDCouldn’t be implemented because of high cost of

Bluetooth module. Making separate controller required another Bluetooth module working in Master mode.

Bluetooth of laptop or android set is used as Master (Host).

PROPOSED BUT NOT IMPLEMENTED PARTS

• Interface using Android devices (tablets and smart phones)

• High current capacity voltage regulator

• TTL-CMOS bidirectional voltage level converter

EXTRA PARTS IMPLEMENTED

CONCLUSION

• Our final product is HIGH POWER AUDIO AMPLIFIER.

• We have build BLUETOOTH INTERFACE between system & digital control.

• Finally, it has it’s own GUI BASED CONTROL APPLICATION which can be operated through Bluetooth enabled windows based devices.

• Control via Android based smart-phones using serial terminal emulator for android (BlueTerm)

FURTHER ENHANCEMENT

• Multichannel audio output (2.0 ch, 5.1ch)

• Wireless audio input via Bluetooth.

• Increasing steps for tone and volume control.

• Development of control applications on other platform (iOS, Mac, Linux )

• Other audio effects (Echo, delay, compression, reverb etc.)

BOOKS:

• A.S. Sedra and K.C. Smith, “Microelectronics Circuits Theory and Application”, 5th edition, Oxford University Press

• Muhammad Ali Mazidi, “8051 Microcontroller and Embedded Systems”, Prentice Hall, 2006

• Douglas Self, “Audio Power Amplifier. Design Handbook”, 3rdedition.

WEBSITES:

• http://hackaday.com/2011/06/27/stereo-amplifier-with-digital-volume-control/

• http://www.diyaudio.com/forums/solid-state/

• http://en.wikipedia.org/wiki/Bluetooth

• http://www.bluetooth.com/

• http://www.aaroncake.net/circuits/volume.asp

REFERENCES

THANK YOU FOR YOUR INTEREST!