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Level 0 Functional Schematic. Team I: Guitar Amplifier with Bluetooth Input. Nick Seliga (Lead), Robert Stanton, Amer Dalaq , and Logan Sammons. Level 1 Functional Schematic. Work Breakdown Structure. Nick Group coordination and communication with customer
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Level 0 Functional Schematic Team I: Guitar Amplifier with Bluetooth Input Nick Seliga (Lead), Robert Stanton, AmerDalaq, and Logan Sammons
Work Breakdown Structure • Nick • Group coordination and communication with customer • Guitar preamp design and testing • Signal Boost, Tone Control, Variable Gain Stage, and Volume Control • PCB layout design • Logan • Bluetooth Input design and testing • Bluetooth Module, Programming Interface, and Line Level Control • PCB Prototype soldering • Robert • Battery system design and testing • Charging Input, Input and Output Current Limiters, Regulators, and integration into enclosure • Prototype construction • Amer • Amplifier design and testing • Summing Amplifiers, Power Amplifier, and Speakers • Prototype construction
Signal Flow • From Handheld Device (Cell Phone, iPod, MP3 Player) • Through RN-52 Bluetooth Device • Out to Amplifier to be Mixed With Input Guitar Signal
Bluetooth Features • Operating Frequency 2.4 – 2.48 GHz • Maximum Data Rate 3 Mbps • Operation Range 10 m or 32.81 ft • Supply Voltage 3.0V to 3.6 V • Working Current 30 mA • Standby Current 0.5 mA • Ability to be programmed using UART using micro-USB • Firmware upgrade ability using micro-USB • Volume Control with potentiometer connected to output of Bluetooth module before amplifier • Ability to tell whether Bluetooth module is connected using blue LED
Testing Bluetooth • Test manufacturer’s specifications on range of operation • Test for interference in operating frequency range (Wifi) • Test quality of output signal before amplifier to insure low noise due to potentiometer volume control • Test amp draw of circuit when streaming audio to amplifier as well as when in standby mode for battery efficiency considerations. • Select value of potentiometer so that range of volume is maximized from high resistance to low resistance
Guitar Preamp • Responsible for shaping the sound of the guitar portion of the amplifier • Uses 3 potentiometers for tone, gain, and volume control • High input impedance, which guitar pickups are intended to feed • Operates on 5 V
Parts • Surface mount resistors and capacitors • PCB mount Potentiometers • Fairchild Semiconductor MMBFJ201 n-channel JFET • Texas Instruments LME49740 high performance, high fidelity audio op-amp • Evaluation • Circuit will be built on a breadboard with through hole components from the Shop to test functionality and dial in the sound • Individual sections will first be tested separately, then together as a system
Battery and Distribution • Lithium Polymer (LiPo) batteries are advantageous due to their flat, compact design • Require limited charging and discharging currents for longevity and safety • Require product shutdown at specified voltage • Two LiPo batteries in series providing 7.4 V • Capacity should be at least 800 mAh (approx. max discharge of 1C) • Capacity desired to be closer to 3200 mAh (4 hours of play at approx. max discharge) • Capacity will be dictated by space limitations/considerations
Power Concept Schematic Outside Current & Voltage LiPo Voltage VBUS Source Controllers Batteries Regulators
Battery Evaluation • Ensure proper operation of LiPo Charging Controllers • Ensure Batteries charge at same rate • Ensure product at full power draw (High Total Volume) does not exceed recommended battery discharge rates • Check charging time • Check total play time • Determine Circuit Shutdown at Batteries’ minimum voltage
Characteristics/Features • Stereo amplifier operates at range of ~5 V • Output ~2.6 W for a 4 Ω load • Built-in thermal load protection • When the junction temperature reaches 160⁰ C, the amplifier output stage is disabled until the temperature cools by 15⁰ C. • Has low harmonic distortion of 0.01% • Low power saving features such as: • 2 mV Vos (minimizing DC current drain through speakers) • 12 mA supply current