PROJECT MEETING II

Theremin

THEREMIN

VariableOscillator

FixedOscillator

Detector

Pitch Control

VariableOscillator

VolumeTuning

Volume Control

FreqSwitch

Theremin

Tuner Out Signal

Footswitch

Audio Out

Freq-VoltageConverter

PIC controllerwith A/D

Discrete Frequency Controller

14-bit D/AV/F

Converter

VCAProcessor

Voltage ControlledAmplifier

Output Control

Theremin Modular Design

Theremin

VPO and FPO Circuits

Theremin

VPO and FPO Outputs

Theremin

Detector Circuit

Theremin

Beat Frequency Output Range

f = 1 / T = 1765.4 Hz

T = 0.566 msec

CMAX = 6 pF gives

fMAX of 1765.4 Hz

CMIN = 2 pF gives

fMIN of 109.9 Hz

f = 1 / T = 109.9 Hz

T = 9.1 msec

Theremin

Lab Results

VariableOscillator

FixedOscillator

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

Theremin

Beat Frequency Oscillator

VariableOscillator

FixedOscillator

Detector

290 – 288 kHz

292 – 288 kHz

Audio:

80 – 850 Hz

•Beat frequency oscillator functions fairly well.

•Audio range falls short of design requirement.

Theremin

Footswitch

Footswitch

Tip

Ring

AmplifiedAudio Out

Audio InControl Signal

Normally Closed

• Stepping on footswitch enables antenna volume control.

• Releasing footswitch disables Audio Out.

-12V

Control Voltage:

0V full volume

-12V no output

Theremin

Discrete Mode Overview

Frequency/Voltage

Converter

PIC controller with 10 bit A/D

14 bit

D/A Converter

Voltage/Frequency

Converter

110-1760 Hz continuous beat frequency from detector

0.3-5 V continuous voltage range

Binary representation of selected output level

Resulting discrete voltage level

Desired note within 0.1% error

Theremin

Frequency-to-Voltage ConverterRequirement Current Status

Input frequency 110 – 1760 Hz 110 – 1760

Output voltage 0.3 – 5.0 V 0.27 – 2.51 V

LM741 LM239

Theremin

F –V ConverterFrequency to Voltage Converter

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 500 1000 1500 2000

Input Frequency (Hz)

Ou

tpu

t V

olt

ag

e (

V)

Ckt OutputIdealLinear (Ckt Output)

Simulation

Lab Results

Theremin

Microchip Program

Flow Chart of the Microchip Program

Theremin

V - F Converter

Voltage to Frequency Converter

0

200

400

600

800

1000

1200

1400

1600

1800

0 2 4 6 8 10

Vout (V)

Fin

(H

z)

Circuit Output

Linear (Circuit Output)

Requirement Current Status

Input Voltage 0 – 12 V 0.01 – 9.6

Output Frequency 110 – 1760 Hz 156 - 1760 Hz

Theremin

Tuner Out Circuit

Gain = -RF / R1 = -46k / 13k = 3.54 V/V

To

Tuner

Theremin

Tuner Out Results

Gain = Vo / Vin = 1.4154 / 0.4 = 3.54 V/V

Theremin

SummaryBeat 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

Theremin

Questions?