ThereminTheremin TeamResponsibilitiesMotivationSolutionsDesign RequirementsTheremin Modular DesignPitch ControlOscillatorsVariable Pitch OscillatorFixed Pitch OscillatorDetectorSlide 13Volume ControlOscillator DriftDiscrete Frequency ControllerFrequency-Voltage ConverterSlide 18Slide 19PIC controller and A/DMicrochip ProgramVoltage-Frequency ConverterSlide 23Slide 24Tuner Out CircuitTuner Out ResultsFootswitchCost AnalysisDesign SummaryMarket PossibilitySenior Design IIFuture WorkAcknowledgementsDemonstrationThereminThereminDesign Review IIDouglas [email protected] [email protected] Jun-Fey [email protected] Beng [email protected]. Raymond Winton Faculty Advisor ThereminTheremin TeamThereminResponsibilitiesDouglas Beard:Analog to DigitalDigital to AnalogMicroprocessorMicah Caudle:Oscillators.Beat frequency detector.Volume CircuitWay Beng Koay:Frequency to Voltage ConversionVoltage to Frequency ConversionJeffrey Jun-Fey Wong:Output StageFootswitch CircuitTuner OutLack of Reference: Since the thereminist does not actually touch the theremin, he has no point of reference for playing certain notes and nothing to steady his hand.Continuous Volume: Staccato playing or quick stops and starts are difficult with the theremin because of continuous volume control.ThereminContinuous Pitch: The theremin is a continuous pitch instrument like trombone or violin which makes playing in tune difficult, especially for beginners.MotivationThereminTuning: A reference for tuning will be provided for silently locating starting pitches and pitch verification during practice. Theremin will interface with common tuners.SolutionsFoot Pedal: A foot pedal will allow instantaneous mute and unmute in order to produce easier staccato. Dual Mode Theremin: A more versatile theremin will be able to switch from the original continuous frequency mode and a new discrete frequency mode that produces scales automatically.Theremin•Footswitch for staccato articulationDesign Requirements•Tuner signal independent of volume control•Box dimensions of 18”x6”x4” and weight under 8 lbs.•Four octave frequency range: 110 Hz to 1760 Hz•Automatic scales with error < 0.1%•Parts cost less than $80VariableOscillatorFixedOscillatorDetectorPitch ControlVariableOscillatorVolumeTuningVolume ControlFreqSwitchThereminTuner Out SignalFootswitchAudio OutFreq-VoltageConverterPIC controllerwith A/DDiscrete Frequency Controller14-bit D/AV/FConverterVCAProcessorVoltage ControlledAmplifierOutput ControlTheremin Modular DesignThereminThereminPitch ControlVariableOscillatorFixedOscillatorDetectorPitch ControlRequirements: (1) Output an audible sinusoidal frequency between 110Hz and 1760Hz.(2) Achieve the change in frequency with 1 to 17 inches hand distance from antenna.VariableOscillatorFixedOscillatorDetector290 – 288 kHz292 – 288 kHzAudio:110 – 1760HzThereminOscillatorsVPO and FPO schematicThereminVariable Pitch OscillatorSimulation resultVPOMAX 291 kHz VPOMIN 288kHzThereminFixed Pitch OscillatorFPOMIN 288kHzSimulation resultFPOMAX 292 kHzThereminDetectorRequirement:Extract beat frequency from variable and fixed oscillators(heterodyning)ThereminDetectorSimulationSimulation result Circuit outputBeat frequency range 70 Hz – 1850 HzSensitivity 104.5 Hz/inch (from 1 – 17 inches)ThereminVolume Control •Functioning on breadboard circuit•Not working in box•Needs more testing and debuggingVolume vs. Distance00.20.40.60.811.21.41.60 2 4 6 8 10 12 14 16Distance (inches)Audio (pk-pk)ThereminOscillator DriftProblem:Temperature induced drift cause unstable oscillator frequencyFactor: Temperature sensitive components in the oscillator circuitSolution:(1) Adjust FPO on the fly with potentiometer(2) Improve temperature stability by up-grading temperature sensitive components(3) Insert a feedback loop into circuit to reduce driftingThereminDiscrete Frequency ControllerFrequency/VoltageConverterPIC controller with 10 bit A/D14 bitD/A ConverterVoltage/FrequencyConverter110-1760 Hz continuous beat frequency from detector0.3-5 V continuous voltage rangeBinary representation of selected output levelResulting discrete voltage level Desired note within 0.1% errorThereminFrequency-Voltage ConverterRequirements:(1) Take input of sinusoidal frequency between 110Hz and 1760 Hz and output DC voltage between 0.3V and 5 V(2) Sensitivity 2.5mV/Hz ± 1mV/Hz.(3) Convert the sinusoidal signal to pulse signal to meet the requirement of the LM331, slew rate < 0.05V/us.ThereminFrequency-Voltage ConverterProblem: Slew rate of the opamp comparator > 0.05V/usDesign factor: time, space and costSolution: LM 239 comparatorGeneral purpose opamp – LM 741 Integrated circuits comparator – LM 239ThereminFrequency-Voltage ConverterRequirement Sensitivity(to allow PIC control)2.5mV/Hz ± 1mV/HzAchieved sensitivity 1.6mV/HzThereminPIC controller and A/D•Correct table values still need to added to code•The microcontroller now takes in a voltage and outputs a corresponding stepped number.•Microcontroller then needs to be connected to the other portions of the Discrete Frequency Controller.Weeks1 2 3Discrete Frequency ControllerDebug Micro-codeTestingAssemble on BoardProjected timeline for meeting all requirementsThereminMicrochip ProgramFlow Chart of the Microchip ProgramThereminVoltage-Frequency ConverterRequirement: In order to achieve the 0.1% frequency error, the voltage-frequency converter has to meet the following requirement.Sensitivity: 146.67 Hz/V ± 25Hz/VLinearity: ± 0.11Hz worst-caseThereminVoltage-Frequency ConverterRequired Sensitivity 146.67 Hz/V ± 25Hz/VAchieved sensitivity 160.31 Hz/VRequired linearity ± 0.11 Hz worst case (0.1% of 110 Hz)Achieved linearity ± 20.7 Hz (std deviation)ThereminVoltage-Frequency ConverterProblem: Error exceeds 0.1% frequency accuracy Musical sinusoidal output signal Solution: Re-design using a more accurate sine wave generator• Voltage controlled oscillator• Numerical controlled oscillatorLowest frequency Highest frequencyThereminTuner Out CircuitRequirement:Provide signal for common tuner (frequency discriminator)Gain = -RF / R1 = -46k / 13k = 3.54 V/VToTunerDetectorThereminTuner Out ResultsSimulationCircuit OutputActual Gain = Vo / Vin = 1.4154 / 0.4 = 3.54 V/VThe output signal meets the requirement for common tunersThereminFootswitchFootswitchTipRingAmplified Audio OutAudio InControl SignalNormally OpenRequirements:
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