Ultrasonic Transducer

Discussion in 'The Projects Forum' started by Tate, Jun 3, 2010.

  1. Tate

    Thread Starter New Member

    Mar 8, 2010
    11
    0
    I am trying to make a ultrasonic signal generator and transistor amplifier for experimenting in sonochemistry. I am a machinist by trade trying to learn electronics.

    The transducer I am trying to power is a 40KH 70W unit. Here is the specifications,
    http://www.steminc.com/piezo/SMBLTD45F40H.asp

    I used the signal generator on my Picoscope 2203. The signal was a 40KH square wave with a 50% duty cycle.

    Being new to electronics I figured a regular audio amplifier would work. I used a Sony Xploid amplifier and got little results. The transducer vibrated enough to be barely audible. Thinking I needed more power I built a 500W amp from Elliot Sound Products(project 68.) The amp worked great on music but again it didn't work on the transducer.

    I have since found this site and have studied a lot about transistors and believe that I need to use IGBT transistors instead of bipolar transistors.

    Could IGBT transistors be used to drive a circuit like this? Can I use a standard current mirror and differential amp for a pre-amp and use IGBT transistors for the power stage?

    Is a square wave the normal signal used on ultrasonic transducers and can I use a 555IC in astable mode to provide the signal or does the signal need to be a AC square wave?

    Thank you for taking the time to read this post and I appreciate any help that you can offer.

    JT

     
  2. Bychon

    Member

    Mar 12, 2010
    469
    41
    For starters, one definition of ultrasonic is, "higher than humans can hear". As in, no wonder you can't hear it.

    Second, most audio amplifiers do not amplify ultrasonic frequencies because people can't hear them.

    Your measuring device (human ears) is inappropriate for this test.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
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    Suggested operating voltage- 450 to 500V-- Ouch! Sinewave OK- i think.
     
  4. Tate

    Thread Starter New Member

    Mar 8, 2010
    11
    0
    I have the transducer connected to a mechanical amplifier and "horn" in a similar fashion to this video. Please notice how there is a audible tone similar to that of a ultrasonic cleaner.

    http://www.youtube.com/watch?v=5eU2eBdIkRg

    I looked at the data sheets of the transistors used; mpsa42, mjl21193 and mjl21194 all state that they can handle the higher frequencies.
     
  5. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    the noise you hear in the video is from the magnetic stirrer spinning at the bottom of the container.......

    Most ultrasonic devices I have seen that are used in studying the cavitation effect have all been based on piezo transducers, not ultrasonic transducers....
    check this out >>http://www.powerultrasonics.com/content/anatomy-ultrasonic-system#

    B. Morse
     
    Last edited: Jun 4, 2010
  6. John P

    AAC Fanatic!

    Oct 14, 2008
    1,632
    224
    I wouldn't call this a beginner project by any means. You need to generate a high-frequency output with significant power delivery and at high voltage--not trivial stuff.

    Just doing a quick Google search on "ultrasonic power amplifier" led to this project by two Lithuanians (Yes it's in English). They generated a low-voltage drive and then had a transformer to step it up to output level:

    http://www.ktu.lt/ultra/journal/pdf_58_1/58-2006-Vol.1_06-L.Svilainis.pdf
     
  7. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    You can actually do small scale studies using one of those fog devices that you see people putting in their small fountains and such....

    like this unit here >>http://www.kineticfountains.com/the-fogger.asp?idcategory=210

    B. Morse
     
  8. Tate

    Thread Starter New Member

    Mar 8, 2010
    11
    0
    Here is a video showing the noise without a magnettic stirrer.

    http://www.youtube.com/watch?v=G7EHyyoc86A

    Unfortunately what I am wanting to test needs more power than a fogging setup will put out.

    Thank you for the link to that article, I did not have that one.

    Is it possible to build this using a lower voltage than the 300-500V that the datasheet talks about using transistors to provide the power amplification and not an output transformer? Possibly using the IRF 510 transistors in parallel?
     
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