Krazatchu Design Systems

1) Schematic  2) Power (blue) & Phase Angle (pink)  3) Resonant mode frequency sweep  4) AD9833 (MSOP) breakout board

As a part of a larger project, the requirement to drive a 200 watt  ultrasonic probe at it’s media-varying resonant frequency was realized. An Atmega8 was used to manage feed back and instruct an AD9833 DDS to output the correct frequency.

Two methods were used as resonant  mode feedback, phase angle and current sense. The phase angle was measured by detecting and comparing zero crossing of the current and zero crossing of voltage waveforms. The current sense was a common low side sense fed into the ADC of the controller.  Data was captured via rs232 and logged in excel.

The ultrasonic probe was CNC machined according to vibrational analysis performed with FEA. Theoretical simulation and experimental results matched within 1/2 of  a Hz.

An AVR based R2R DDS with controls for offset and gain.  Sine, sawtooth, square and triangle waveforms are stored in look up tables in the Atmega16?s internal flash. An LM358 is used to realize the offset and gain. The frequency range is 0 to 65534 Hz in 1 Hz steps. The enclosure is CNC cut from a CAD file.

1) Schematic   2) Board  3) Enclosure 4) 20kHz Sine wave after RC filter (below)

A class AB power amp was designed to run a 200 watt ultrasonic transducer. The topology is a qsc cascode type amp running from +/- 80 volts DC.

1) Schematic  2) Board  3) Amp  4) Enclosure  5) Scope Trace