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Unplugged A Solar Powered Audio Amplifier With DSP Effects Group 16 Gretchen Rivera Hugo Castellanos Sandra Munoz 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. 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 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 Overall Block Diagram Audio Subsystem Preamplifier, Equalization, Mixer and Audio Amplifier Audio Subsystem Overview 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 Testing Equipment • LM386 Audio Amplifier 4 Ohm RCA Speaker •ONLY TO TEST FUNCTIONALITY • Rigorous electrical testing will be conducted eventually • DC offset, RF Noise, Frequency Response 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 SSM2019 Implementation Equalizer • Specs called for an EQ with at least +/- 10 dB of dynamic range • Best Solution: Baxandall Tone Control Circuit 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 Baxandall Circuit Fc=500Hz Filter Frequency Response •Frequency response with potentiometers at the center position •Maximum deviation of 0.191 dB due to virtual ground Filter Frequency Response • Frequency Response with potentiometers fully CCW • Maximum Cut of 12 dB at both sides of the band Filter Frequency Response • Frequency response with potentiometers fully CW • Maximum Boost of 12 dB at both sides of the band Equalizer Implementation Problems • Noise • Breadboard Capacitance Solutions • Use Vero board • Use more accurate components 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 Power Subsystem Battery, Solar Panel, Battery Charger Power System Overview Solar Panel Battery Charger Voltage Divider LCD Battery 9V Regulator Microcontroller Audio System DSP Effects Batteries Type Pros Cons Lead-Acid Cheap 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-ion Highest energy density, Most expensive, circuit light-weight, faster charge protection times Summary of The Current of Different Components Components Current Virtual Ground TLE2426 400μA (1) Preamplifier SSm2019 4.6mA (2) LME 49740 Equalizer 20mA (1) LME 49720 10mA (1) Amplifier TDA1562Q 90mA (1) LCD 300μA (1) Microcontroller 500μA (1) DSP Effects 100mA (1) BAXXBC0WT 9V Regulator 9 130μA (1) Miscellaneous 70mA Total 300mA 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 Solar Panels Type Pros Monocrystalline Silicon Max efficiency 22.7%, Most expensive produce voltage even at low lights conditions Polycrystalline Silicon Cheaper than monocrystalline Amorphous Silicon Least expensive, can continue to charge at cloudy conditions Cons Not able to charge when weather is cloudy Lowest efficiency 5-7 %, short lifetime 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 IV Curve of Solar Panel Battery Charging Circuit Buck configuration DC/DC converter Battery Charger Prototype Enclosure Considerations Crown CE1000 •19” X 5.25 X 12.25” • Rugged Steel •5.3 lbs Yamaha BR 15 Speaker •19.1” X 25.8” X 14.4” (W,H,D) •15 inch horn •200W RMS • 30 lbs Enclosure Considerations SKB 4 unit rack case •22.50” X 9.5” X 21.50” •12 Lbs Enclosure Concept • Amplifier enclosure mounted inside SKB case Enclosure Concept DSP and Monitoring Subsytem Microcontroller, DSP unit and LCD 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. Microcontroller Block Diagram 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. Arduino Mega2560 LCD Nokia 3310 • 2.7-3.3V operation 2.7 to 5.5V operation LCD drive power 3.3 to • Graphical LCD 11V • 48 row, 85 column Provides a choice of size output • 40X38 mm size 240 character fonts • Not readily available Widely used • Costs about $6. Costs about $7 HD 44780 • • • • • • HD 44780 • Availability • Widely used in previous projects • Did not need graphical functionality • 20X4 provided enough space • Easily interface with Arduino Mega. HD44780 HD 44780 • Solar Panel voltage and current will be displayed as well as battery voltage. 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. 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 BTSE-16FX 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 Administrative Budget Item Price 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 board Free Mis. Audio Connectors $ 10 Amplifier enclosure Free 4ohm 15 inch speaker Free PCB $ 100 Faceplate TBD Total Spent $ 442 Original Budget $ 1000 Progress Overall (60%) PCB (10%) Testing (60%) Prototyping (60%) Parts (90%) Design (95%) Research (95%) 0 20 40 60 80 100 Questions??? Unplugged A Solar Powered Audio Amplifier With DSP Effects Group 16 Gretchen Rivera Hugo Castellanos Sandra Munoz