1. Unplugged A Solar Powered Audio Amplifier With DSP Effects Group 16 Gretchen Rivera Hugo Castellanos Sandra Munoz

2. Project Description The “unplugged” sound system is a solar powered audio amplifier that provides the freedom to play music anywhere without having to be attached to the power grid. It provides inputs for not only musical instruments, but also for microphones and an iPod or MP3 player. The “Unplugged” also provides a DSP effects unit which allows the user to choose an audio effect and a respective input to apply the effect to.

3. Goals and Objectives Power management system must be capable to fully charge and run off a battery. User must be able to pick which of the effects to apply and which analog input to apply them to. Inputs for microphone, instrument and line signal User must be able to continuously monitor parameters such as battery voltage, solar panel voltage and current by the means of a display. Must be portable

4. Specs and Requirements Should weight less than 30 pounds Capable of delivering a minimum output of 30 Watts RMS Capable of operating for 90 minutes Each analog input has to be equipped with an EQ circuit with a dynamic range of +/-10 dB To incorporate three DSP audio effects including reverb The system must be able to run off a 12V battery The battery must be charged solely by a 20W solar panel The system will include 1 microphone input for low impedance microphones, one ¼ inch instrument input and an RCA input for auxiliary audio sources

5. Overall Block Diagram

6. Audio Subsystem Preamplifier, Equalization, Mixer and Audio Amplifier

7. Audio Subsystem Overview

8. Virtual Ground TLE2426 “The Rail Splitter” from TI Splits input voltage in half Provides virtual ground so op-amps can be biased Consumes only 400 µA from the 9 V LDO

9. Testing Equipment LM386 Audio Amplifier4 Ohm RCA Speaker ONLY TO TEST FUNCTIONALITY Rigorous electrical testing will be conducted eventually DC offset, RF Noise, Frequency Response

10. Preamplifier IC SSM2019 from Analog Devices 8 lead Plastic Dual-in-line-package (PDIP) Wide range power supply: 4V-18V Will be operating at 9V with virtual ground Low Quiescent Current: 4.6 mA Voltage gain of up to 3500 Excellent noise figure @ 0.2 µV between 20 Hz – 20 kHz ONLY ONE EXTERNAL COMPONENT

11. SSM2019 Implementation

12. Equalizer Specs called for an EQ with at least +/- 10 dB of dynamic range Best Solution: Baxandall Tone Control Circuit

13. Equalizer IC LME 49740 from National Semiconductor Quad high performance, high fidelity audio operational amplifier 14 lead DIP Package Wide supply voltage: 4V to 17 V Quiescent current of 20 mA for all 4 amplifiers Excellent noise figure: 0.4 uV in the full audio range Unity Gain Stable Design Specific Considerations FL=300 Hz, FH= 1kHz 2 Amplifiers for EQ, 2 for line level signal mixing

14. Baxandall Circuit Fc=500Hz

15. Filter Frequency Response Frequency response with potentiometers at the center position Maximum deviation of 0.191 dB due to virtual ground

16. Filter Frequency Response Frequency Response with potentiometers fully CCW Maximum Cut of 12 dB at both sides of the band

17. Filter Frequency Response Frequency response with potentiometers fully CW Maximum Boost of 12 dB at both sides of the band

18. Equalizer Implementation Problems Noise Breadboard Capacitance Solutions Use Vero board Use more accurate components

19. Audio Amplifier IC TDA1562Q from NXP Semiconductor 70 Watt Hybrid class H audio amplifier 17 lead SIP Package Operates between 8V and 14.4 Volts Quiescent Current of 90 mA 50 W RMS Power with 9V rail

20. Power Subsystem Battery, Solar Panel, Battery Charger

21. Battery 9V Regulator Audio System Voltage Divider LCDMicrocontroller Battery Charger Power System Overview Solar Panel DSP Effects

22. TypeProsCons Lead-AcidCheap price, stable at high temperatures, have multiple cycles Low energy density, cannot be completely discharged Nickel-Metal Hydride Better cycle life than lead acid, creates no memory High self-discharge 20% per month, circuit protection Lithium-ionHighest energy density, light-weight, faster charge times Most expensive, circuit protection Batteries

23. ComponentsCurrent Virtual Ground TLE2426400μA (1) Preamplifier SSm20194.6mA (2) LME 49740 Equalizer20mA (1) LME 4972010mA (1) Amplifier TDA1562Q90mA (1) LCD300μA (1) Microcontroller500μA (1) DSP Effects100mA (1) BAXXBC0WT 9V Regulator 9 130μA (1) Miscellaneous70mA Total300mA Summary of The Current of Different Components

24. Battery Chosen Power-Sonic 12V/7 AH Sealed Lead Acid (AGM) Battery Valve regulated allows safe operation in any position Measures L: 5.95 in W: 2.56 in H: 3.70 in High Shelf Life (% of nominal capacity at 68°F (20°C)) 1 Month 97% 3 Months 91% 6 Months 83% Weights 4.8 lbs

26. Solar Panels TypeProsCons Monocrystalline Silicon Max efficiency 22.7%, produce voltage even at low lights conditions Most expensive Polycrystalline Silicon Cheaper than monocrystalline Not able to charge when weather is cloudy Amorphous SiliconLeast expensive, can continue to charge at cloudy conditions Lowest efficiency 5-7 %, short lifetime

27. Solar Panel Chosen 20 Watt Solar Panel DC 12V Monocrystalline PV Module by HQRP Open Circuit Voltage (Voc): 21.6V Short Circuit Current (Isc): 1.3A Maximum Power Voltage (Vmp): 17.2V Maximum Power Current (Imp): 1.17A Dimensions: 420x420x25 mm

28. IV Curve of Solar Panel

29. Battery Charging Circuit Buck configuration DC/DC converter

30. Battery Charger Prototype

31. Enclosure Considerations Yamaha BR 15 Speaker 19.1” X 25.8” X 14.4” (W,H,D) 15 inch horn 200W RMS 30 lbs Crown CE1000 19” X 5.25 X 12.25” Rugged Steel 5.3 lbs

32. Enclosure Considerations SKB 4 unit rack case 22.50” X 9.5” X 21.50” 12 Lbs

33. Enclosure Concept Amplifier enclosure mounted inside SKB case

34. Enclosure Concept

35. DSP and Monitoring Subsytem Microcontroller, DSP unit and LCD

36. Arduino Mega 2560 Preassembled with ATmega2560 256KB of flash memory 4KB EEPROM 54 digital input/output pins 16Mhz clock 5V operating voltage. Programmable in C.

37. Microcontroller Block Diagram

38. Arduino Mega2560 Will monitor solar panel voltage and current. Will also monitor battery voltage. Will interface with LCD in order to display these values Will run a charger state machine with four states, on, off, bulk and float which will help determine what the state of the charger should be.

39. Arduino Mega2560

40. LCD HD 44780 2.7 to 5.5V operation LCD drive power 3.3 to 11V Provides a choice of size 240 character fonts Widely used Costs about $7 Nokia 3310 2.7-3.3V operation Graphical LCD 48 row, 85 column output 40X38 mm size Not readily available Costs about $6.

41. HD 44780 Availability Widely used in previous projects Did not need graphical functionality 20X4 provided enough space Easily interface with Arduino Mega.

42. HD44780

43. Solar Panel voltage and current will be displayed as well as battery voltage.

44. ADAU1702 issues Reverb comes standard on library but chip does not support it. The ADAU14x family supports reverb Development board is about $400. Would not meet budget or specs.

45. BTSE-16FX Effects Module Provides 16 different digital audio effects 5V power supply 64 X 35 mm in size Costs about $16 dolars. Effects will be controlled using a 4 bit grey code rotary encoder

46. BTSE-16FX

47. Possible Problems PCB Design Eagle is inadequate for our needs 100 mm x 80 mm is too small! Not sure how to transfer programmed ATmega to final PCB. Heat Dissipation Forced air- extra power consumption

48. Administrative

49. Budget ItemPrice Solar Panel$ 108.95 Arduino Mega$ 59.65 Battery$ 21.60 IC’s$ 44.63 DSP FX$ 15.00 LCD$ 7.00 Heatsinks$ 9.00 Capacitors$ 12.38 Breadboards$ 35.80 Potentiometers$ 29.53 Perforated boardFree Mis. Audio Connectors$ 10 Amplifier enclosureFree 4ohm 15 inch speakerFree PCB$ 100 FaceplateTBD Total Spent$ 442 Original Budget$ 1000

50. Progress

51. Questions???

52. Unplugged A Solar Powered Audio Amplifier With DSP Effects Group 16 Gretchen Rivera Hugo Castellanos Sandra Munoz