dynamic impedance matching?

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#1
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my research is ultrasonic generator, its function is to drive transducer. transducer's equation please see my attachment.

Attachment(s): 

Our Martians are beginning to learn AVR

Last Edited: Tue. Oct 2, 2007 - 03:19 AM
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Why not get a big amplifier to drive the speaker and just ignore the impedance mismatch? Whats the big picture? What are you trying to invent? Or are you just doing some pure academic research to get a grade and pass a course?

Imagecraft compiler user

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Why bother? Unless you need every last microwatt out of the transducer, it is probably more work than its worth.

And, I really dislike the "meat" of a posting to be in an attachment that you have to open just to see what the question is. This is just my quirk.

Jim Wagner
Oregon Research Electronics, Consulting Division
Tangent, OR, USA

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Not too mention that the document seems to be a Word document which I won't open from a work computer for no amount of money.

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And what does "dynamic" impedance matching means?

The transducer is most likely capacitive, so it has complex impedance which is not going to change, so just go for "static" impedance matching...

- Jani

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I think the concern is less that it is capacitive and more that it is temperture dependent.

There are system that do this. They automatically tune an antenna load t a transmitter. But, they have motorized coils and capacitors, an SWR bridge, and a whole micro to drive it. I don't think that this sort of thing is worth the effort in this kind of application.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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i have shared my circuit with you, the attachment is in the toppest.
my tutor asked me to develop a bigger amplifier, i have tried a 100w AB class amplifier from a book, but it failed. i really want to try D class amplifier, but my highest frequency is 200khz, i know max5069's oscillator frequency can reach 2.5Mhz, i don't know whether is enough. by the way ,max5069 can use external frequency, i don't know whether it can reach higher than 2.5MHz, if it is able to do that , it will be much easier for me.

Our Martians are beginning to learn AVR

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I could only suggest you use a H bridge driver into a transformer to match the impedance of the piezo. You could then have the piezo as part of a tuned circuit so all you need to do is vary the frequency to find resonance. You would only need to resort to class D (pwm) if you needed to vary the output power.

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Class D (and E) can be used to get the efficiency up. Class D and E are widely used for new AM broadcast transmitters to 1.5MHz. Class AB should work just fine.

What is the actual operating (output) frequency?

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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By the way, a piezo transducer will be mostly capacitive with an effective series (or shunt) resistor representing the power emitted as audio power.

Thus, thinking of a 100 power amplifier is not very useful. Power is defined with respect to a resistor load, and the transducer does not give you that unless you cancel out the reactance with some of the opposite sign (ie, inductance).

Your Class AB amplifier should work just fine. When you say it didn't work, what evidence do you have? The amplifier might not seem to work if the load is almost all capacitive and is not properly matched to the amplifier.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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Keep in mind this is the same guy who asked for help on a circuit he created with software he pirated.

Jim
'The Rebel'

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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I know that very well.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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I also noticed he mentions a tutor. This troll is a student looking for someone else to do his home work.

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Yes, I also thought about that. Been through grad school and in contact with a lot of grad students from foreigh countries. I do know that there are very different attitudes about how "projects" should be done and what level of research the student is expected to do, at what level. It varies immensely from country to country and school to school.

That said, I have no problem answering questions when a student is fumbling, as long as there is evidence that the student has really tried to figure it out himself or herself. To be fair, the OP's project is NOT one that will have a lot of info in the 'net, though he could have problems figuring out where or how to look.

I'm willing to give some technical suggestions as long as it does not rise to the level of solving the problems for him.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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AFAIK, ultrasonic power stages for ultrasonic cleaning baths, use some kind of 'tuned' circuit that stays automatically in tune with the ultrasonic resonant frequency. They don't have too many components, thus circuitry must be simple, but I never managed to put my hands on any schematic, and I also doesn't had the chance to take a deep look at them. IIRC, the usual cleaning baths have some kind of heating to heat the liquid sollution, thus the ultrasonic xduzers work over a broad range of temperatures, thus also changing their resonant frequency and impedance.

Guillem.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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If this is being driven by the DDS you ask about elsewhere, then just change the tuning of the DDS to match the change in the resonance of the transducer matching network.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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And as an addendum to ka7ehk's post: what will the ultrasonic transducer do? Stirr up a bath with cleaning fluid ? Or is it for ultrasound ranging / imaging ?

Nard

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