VFO-005

Variable Frequency Oscillator (VFO)

AD9833 based design.

• Arduino Pro Mini
  • 3.3V/8MHz
• AD9833 Function Generator
• DC to 12.5 MHz
• Rotary Encoder/Breakout Board
• 128x32 OLED
• Breadboard Power Supply
  • 3.3V operation
• Mini-360 Voltage regulator (in case)
  • 5-24 VDC input

AD9833 Function Generator

• Digitally programmable frequency and phase
  • 12.65 mW power consumption at 3 V
  • 0 MHz to 12.5 MHz output frequency range
  • 28-bit resolution: 0.1 Hz at 25 MHz reference clock
  • Sinusoidal, triangular, and square wave outputs
  • 2.3 V to 5.5 V power supply
  • No external components required
  • 3-wire SPI interface
  • Extended temperature range: −40°C to +105°C
  • Power-down option
  • Update Rate: 25(max)
  • VOUT Maximum: 0.65V
  • VOUT Minimum: 38mV
  • VOUT Temperature Coefficient: 200°
  • Input High Voltage: 1.7-2.8V
  • Input Low Voltage: 0.5-0.7V
  • Input Current: 10µA
  • Input Capacitance: 3pF
  • Operating temperature range is −40°C to +105°C; typical specifications are at 25°C

Arduino Pro Mini

• 3.3V
• 8 MHz

Rotary Encoder/Breakout Board

• Includes pushbutton Switch
• Includes Pull-Up resistors
• Needs R/C filter on output for debounce
• Reading Rotary Encoders - Arduino reference
• Simple Rotary Encoder Arduino library
• Library for the Arduino environment for using a rotary encoder as an input

128x32 OLED

• Ebay
• 5V/3.3V operation

Breadboard Power Supply

• On breadboard build

Power Distribution Board - Revision X1

• Two headers with 6x2 pins each
• Six pins bussed together
• Ground connection header
• Rounded Corners
• 4 mounting holes for 4-40 screws

Breadboard

Schematic

Build

• DC jack, power distribution card and Mini-360 voltage regulator

• All of the parts get jammed into the box
• Some are hot glued

• Cutout for OLED
• Running with frequency counter

• Display looks great in person not as good on picture

Measurements

• 10 KHz to 30 MHz
• 20 dB attenuator (gain set in tinySA to -20dB)
• VFO-005 set to 10 MHz
• Sinewave
• VFO set at 10 MHz

• Triangle wave

• Square wave

• Half square wave

• 7 MHz sinewave