PROJECT MEETING II Theremi n THEREMIN

Variable Oscillator Fixed Oscillator Detector Pitch Control Variable Oscillator Volume Tuning Volume Control Freq Switch Theremin Tuner Out Signal Footswitch Audio Out Freq-Voltage Converter PIC controller with A/D Discrete Frequency Controller 14-bit D/A V/F Converter VCA Processor Voltage Controlled Amplifier Output Control Theremin Modular Design

Theremin VPO and FPO Circuits

Theremin VPO and FPO Outputs

Theremi n Detector Circuit

Theremin Beat Frequency Output Range f = 1 / T = Hz T = msec C MAX = 6 pF gives f MAX of Hz C MIN = 2 pF gives f MIN of Hz f = 1 / T = Hz T = 9.1 msec

Theremi n Lab Results Variable Oscillator Fixed Oscillator Detector 290 – 288 kHz 292 – 288 kHz Audio: 80 – 850 Hz Left: VPOmax = 291 kHz Right: VPOmin = 288 kHz Left: FPOmax = 292 kHz Right: FPOmin = 288 kHz Detector Output Waveform

Theremi n Beat Frequency Oscillator Variable Oscillator Fixed Oscillator Detector 290 – 288 kHz 292 – 288 kHz Audio: 80 – 850 Hz Beat frequency oscillator functions fairly well. Audio range falls short of design requirement.

Theremi n Footswitch Tip Ring Amplified Audio Out Audio In Control Signal Normally Closed Stepping on footswitch enables antenna volume control. Releasing footswitch disables Audio Out. -12V Control Voltage: 0V full volume -12V no output

Theremi n Discrete Mode Overview Frequency/Voltage Converter PIC controller with 10 bit A/D 14 bit D/A Converter Voltage/Frequency Converter Hz continuous beat frequency from detector V continuous voltage range Binary representation of selected output level Resulting discrete voltage level Desired note within 0.1% error

Theremi n Frequency-to-Voltage Converter RequirementCurrent Status Input frequency110 – 1760 Hz110 – 1760 Output voltage0.3 – 5.0 V0.27 – 2.51 V LM741 LM239

Theremin F –V Converter Simulation Lab Results

Theremin Microchip Program Flow Chart of the Microchip Program

Theremin V - F Converter RequirementCurrent Status Input Voltage0 – 12 V0.01 – 9.6 Output Frequency110 – 1760 Hz Hz

Theremi n Tuner Out Circuit Gain = -RF / R1 = -46k / 13k = 3.54 V/V To Tuner

Theremi n Tuner Out Results Gain = Vo / Vin = / 0.4 = 3.54 V/V

Theremi n Summary Beat Frequency Oscillator: Functions well Need to increase audio frequency range Volume Control Circuit: Works properly D/A Converter: Functioning linearly and accurately Frequency/Voltage Converter: Works well and approx. linear Box: Need to finish constructing box and install hardware Micro Controller: Programming complete I/O not functioning Footswitch Circuit: Works properly Tuner Out Circuit: Works properly

Theremi n Questions?