Published on March 7, 2014
BLUETOOTH CONTROLLED HIGH POWER AUDIO AMPLIFIER Thapathali Campus Final Presentation 2013 PRESENTED BY: BIJAY RAJ PAUDEL (ROLL NO: 067/BEX/105) SAGAR MALI (ROLL NO: 067/BEX/133) SUJAN SHRESTHA (ROLL NO: 067/BEX/140)
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 REPRESENTAION OF POWER SUPPLY
BRIEF EXPLANATION OF EACH BLOCK 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 amplifierDifferential 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
COMPUTER GUI • Codes in C# .NET • Uses serial port class provided by .NET library • User interface in WPF
BRIEF EXPLANATION OF EACH BLOCK 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
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) Timer 0 Interrupt Update LCD with Bass, mid, treble and volume’s current value Check interrupt C Serial Interrupt SI
SI Yes C TI=0 Is TI set? Check Keypad Pins No Increase/Decrease volume, bass, mid and treble Send data corresponding pins attached to multiplexers Send updated values to serial port(SBUF) No Is RI set? RI=0 Yes Read SBUF serial port RI ≠0 Update Vol, Bass, Mid Treble value as command received in SBUF Send data to corresponding pins attached to multiplexers
BRIEF EXPLANATION OF EACH BLOCK 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
ALGORITHM FOR KEYPAD CONTROLLER
START Similar to other columns & rows Initialize all ports to zero Output 5 to port 1 Is key pressed? Is R1=0? Yes Initialize all rows to 1 Initialize C2 =0 & other to 1 Initialize C1=0 other to 1 Similar to other rows R2 to R4 Is R1=0? Output 0 to port 1
PROBLEMS SOLUTIONS • Using transistors in metal cases and larger heat sinks • Proper shielding of preamplifier and connecting wires • Speaker over voltage • spikes damaging the speaker under high volumes 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 • Overheating of power transistors • Noise induction in preamplifier. • Digital potentiometer not available
APPLICATIONS • Auditorium Hall Seminar Presentation Lecture • Theatrical and Concert sound reinforcement • Home Theater System • Car Audio System • Guitar Amplification
PROPOSED BUT NOT IMPLEMENTED PARTS • Limited effect is only implemented because of unavailability of effect IC and complex design if done using discrete components. • Separate independent remote control with LCD Couldn’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).
EXTRA PARTS IMPLEMENTED • Interface using Android devices (tablets and smart phones) • High current capacity voltage regulator • TTL-CMOS bidirectional voltage level converter
CONCLUSION • • Our final product is HIGH POWER AUDIO AMPLIFIER. • 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) We have build BLUETOOTH INTERFACE between system & digital control.
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.)
REFERENCES 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
THANK YOU FOR YOUR INTEREST!
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