IntegTheremin

Features

The Integrated Theremin combines five of our boards into one. The boards included are:

• MiniDuino
  • 16 MHz ATMega 328 processor
  • Arduino UNO Code and IDE Compatible
  • TFT Display connector
• FTDI-USB-TTL
  • USB Interface
  • Board is not powerable from FTDI
• HV Digital Pots
  • 10-bits, 1024 steps
  • Control Frequency and Voltage
• AudioAmp386
  • 3/4 Watt Output
  • Standard RCA phone style connector
• XR-2206 Voltage Controlled Oscillator
  • Waveform Adjustment pot from X3 version of XR-2206

Additional Features

The board has additional features including:

• Advanced Power Supply Design
  • Single +12V power supply input
  • +5V High-Efficiency Switcher to drive logic and High Intensity IR Sensors
    • Previous (separate board) design had a hot regulator on the MiniDuino
      • Due to the current drop of the +12V or +9V to 5V
        • At 200 mA due to the IR sensor cards
  • Total power Measured at 12V, 130 mA = 1.6 Watts
• Dedicated connectors for IR Sensors
• Direct (DC) coupling for Voltage Controlled Oscillator to Audio Amplifier
  • AC cap in series with the previous design led to clipping of the audio
• Added connection to allow Microprocessor to monitor (via A/D) the VCO level for smoother volume control transitions
  • Write all of the D/A serial bits then cycle the FSYNC line to load the D/A
  • Voltage divider
    • Average voltage into divider is 6V
    • Divider resistors 2.2K, 4.7K
    • Divider ratio is (2.2/(2.2+4.7)) = 0.31884
    • 6V * divider ratio = 1.913 V
    • 1.913V * (1023 counts/5V) = 391 counts
    • Peak voltage is 12V - scales to 3.82V which is safely below the 5V input of the A/D
  • Measurements:
    • Minimum count = 278
    • Maximum count = 414
    • Average count = 346
  • Measured the average voltage and it wasn't 6V as expected, it was 5.3V which correlates well to the 346 count
  • Where is the transition supposed to happen with respect to the waveform to write data to the pots?
  • A/D sample rate is around 10K samples/sec
  • If the max freq is 1KHz that means that the waveform is only sampled 10 times per cycle so there could be a large step in volume
  • Start up question as well - the board needs to be autocalibrated at startup
  • May need hardware assist to cycle FSYNC at zero crossing
  • May want to connect the data and clock to the MOSI and SCK lines instead of PIO lines to speed up transfers
  • May want to use logic analyzer to debug
• Board layout is slightly under 50 mm x 100 mm to use SeeedStudio service ($30 for 10 pcs).
• Board has four mounting holes
• New schematic design using hierarchical sheets
• Split Power and ground planes (+12V/+5V) at center of card with jumper to connect GNDs

Block Diagram

[fILE:IThereminBlockX1.png]]

Connectors

J1 - Power Connector

+12V
Ground
J2 -Analog Output - RCA connector

J3 -USB-B Mini

J4 - 5-Way Switch

Ground
Voltage (+5V)
Signal (Keypad)
J5 -Volume GVVS

Ground
Emitter Voltage (5V @ 100 mA)
Sensor Voltage
Sensor Output
J6 - Frequency GVVS

Ground
Emitter Voltage (5V @ 100 mA)
Sensor Voltage
Sensor Output
J7 -Analog Spares

AD5
AD4
AREF
GND
AREF
VCC
J8 - TFT LCD

VCC
Backlight (GND)
RESET
RS
MISO
MOSI
SCK
LCDCS
SDCS
GND
J9(X2)/J10(X1) - Ground jumper

1-2 - GND to GNDA

RV1 - Waveform Adjust

Supported Peripherals