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  1. #1

    ultrasonic generators

    Hi guys! We have this final capstone project in school. We are tasked to build an ultrasonic cleaning equipment like the one attached in this post. I just want to ask if by any chance someone here have done the same project and could provide us some useful information on how to build one. I already searched for ultrasonic generator circuits but could not find any schematic on the web that we can use as reference for our design.

    We need 400-600w of power to drive an array of transducers to create cavitation for cleaning purposes.
    the system has three frequencies of operation 40khz/80khz/135khz.

    any help would be greatly appreciated. TIA!
    Last edited by Undergraduatepowerelecs; 9th July 2018 at 17:56.

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    Re: ultrasonic generators

    You can click on the list of similar topics found by scrolling down this column.
    Also try a forum search on the words
    ultrasonic and transducer.



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    Re: ultrasonic generators

    Hi,

    I already searched for ultrasonic generator circuits but could not find any schematic on the web that we can use as reference for our design.
    A simple internet search gives a lot of schematics.
    You need to refine your search skills.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: ultrasonic generators

    Okay I think I found one article that would help me on this project. But I want to ask regarding the transducer I'am about to use.Click image for larger version. 

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    It is a multi-frequency transducer and I want to know if at these frequencies the transducer would be resonant? The manufacturer did not specify.



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    Re: ultrasonic generators

    None-resonant operation frequencies make no sense, they won't achieve relevant power transfer. You need to hit the "series resonance" (talking in LC equivalent circuit terms) frequency which shows an impedance minimum.

    It's rather normal that an ultrasonic transducer of the cylinder type has multiple resonances at (roughly) integer multiples of the fundamental.



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    Re: ultrasonic generators

    Hello Brad!

    I found this circuit and I just want to modify this to drive my transducers with a driver circuit that has an output that sweeps around the transducer's resonant frequency. What part of this circuit should I modify?

    Click image for larger version. 

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    Re: ultrasonic generators

    Quote Originally Posted by Undergraduatepowerelecs View Post
    Hello Brad!
    What part of this circuit should I modify?
    Sorry, I have no hands-on experience with the IR2110. But you can do a search and see it is a topic in many threads here.

    I suppose the M in a circle is a meter? This can be a plain D'Arsonval type (a shunt is probably necessary). Maybe you can use a digital meter if it is fed reasonably smooth DC current, otherwise it has trouble reading fluctuating waveforms.

    It's important to avoid exceeding the volts & Amperes which your transducers can tolerate. Taking figures in your chart (post #4) the math suggests about 30VAC @ 700mA.

    In your schematic notice F1 is a fuse rated 1A.

    Power comes through the push-pull arrangement Q1 Q2 C3 C5. You can test it for driving one transducer, however to drive several it is probably best to build a power stage for each transducer. That is, all circuitry from B1 (diode bridge) to R14 R15.



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    Re: ultrasonic generators

    Quote Originally Posted by BradtheRad View Post

    Power comes through the push-pull arrangement Q1 Q2 C3 C5. You can test it for driving one transducer, however to drive several it is probably best to build a power stage for each transducer. That is, all circuitry from B1 (diode bridge) to R14 R15.
    Hi! how about the oscillator circuit from 74hc4046 to irf2110? do I have to build it for each transducer or a single osci is enough? Is my block diagram correct?
    Click image for larger version. 

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    Re: ultrasonic generators

    Quote Originally Posted by Undergraduatepowerelecs View Post
    Hi! how about the oscillator circuit from 74hc4046 to irf2110? do I have to build it for each transducer or a single osci is enough? Is my block diagram correct?
    Click image for larger version. 

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    Yes, I expect it will finally look like that.

    To start development I would build enough to test one transducer at a time. See if each works properly with no overheating of components. You may find you need to add heatsinking. If you're very lucky you can drive 2 transducers from a power stage.
    Then build the remaining power stages.

    You may get a sense about whether it's better to vibrate the transducers in unison, or drive them at different frequencies. It depends on effects of resonant action in a 600W system. It may result in better cleaning, or it may shake things to pieces.



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    Re: ultrasonic generators

    Hello Brad! Thanks for the prompt reply!
    I would like to drive each transducer with a signal that is sweeping around the resonant frequency so that standing waves are avoided. Can you give me some suggestions as to how would I modify the oscillator circuit? Thanks!



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    Re: ultrasonic generators

    Quote Originally Posted by Undergraduatepowerelecs View Post
    Hello Brad! Thanks for the prompt reply!
    I would like to drive each transducer with a signal that is sweeping around the resonant frequency so that standing waves are avoided. Can you give me some suggestions as to how would I modify the oscillator circuit? Thanks!
    In the usual sense, standing waves occur under certain conditions, at a particular frequency or frequencies, as reflections reinforce each other in a listening room, or within a conductor, etc. Although this makes it unlikely for you to get standing waves in your project, it doesn't hurt if you sweep through a range of frequencies by using a voltage-controlled oscillator. Control its frequency by feeding it a sawtooth or triangle or sine wave, say at a rate of 1 Hz.
    Or maybe combine two unchanging frequencies, to discourage standing waves. It may be a good idea to test 2 or 3 methods, to find out which creates the best cavitation since you say you want cavitation.



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    Re: ultrasonic generators

    Hello Brad! Do you have a circuit for automatic resonant-seeking circuit. I want to implement it to my design. Thanks



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    Re: ultrasonic generators

    An H-bridge can resemble two op amps in bridged configuration. The aim is to switch current to the opposite direction as soon as a zero crossing occurs. That is how to automatically drive at the resonant frequency.

    A zero crossing can be detected by tapping the ends of a resistor which is inline with the transducer. An op amp is a suitable detector since its output delivers 'snap' action. The resistor cannot be too high ohm value, or else it hampers current to the transducer. You must then design a switching circuit to provide AC to your transducer.

    You can see a simple schematic in my post in the thread linked below. It is two half-bridges. One of them is driven by bias voltage from the resistor. The other half-bridge is driven by the voltage at the node between the first half-bridge.

    https://www.edaboard.com/showthread....=1#post1615523



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    Re: ultrasonic generators

    Quote Originally Posted by BradtheRad View Post
    An H-bridge can resemble two op amps in bridged configuration. The aim is to switch current to the opposite direction as soon as a zero crossing occurs. That is how to automatically drive at the resonant frequency.

    A zero crossing can be detected by tapping the ends of a resistor which is inline with the transducer. An op amp is a suitable detector since its output delivers 'snap' action. The resistor cannot be too high ohm value, or else it hampers current to the transducer. You must then design a switching circuit to provide AC to your transducer.

    You can see a simple schematic in my post in the thread linked below. It is two half-bridges. One of them is driven by bias voltage from the resistor. The other half-bridge is driven by the voltage at the node between the first half-bridge.

    https://www.edaboard.com/showthread....=1#post1615523
    Is it possible to implement these two feature in my cleanig system:
    auto-resonant-seeking
    Sweep



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    Re: ultrasonic generators

    Quote Originally Posted by Undergraduatepowerelecs View Post
    Is it possible to implement these two feature in my cleanig system:
    auto-resonant-seeking
    Sweep
    It sounds as though you hope there is a circuit which performs a frequency sweep, then settles at the frequency which produces the greatest amplitude from the transducers. I'm not sure I can design a reliable analog circuit. A microcontroller might be a good controller for such a task. However it may be redundant to do the seeking action each time you turn on the cleaning machine. I don't think the frequency will change much between uses.

    Or it's probably easier to do by human evaluation. There are various tunable sine-wave generators. You can watch to see which frequency causes your gang of transducers to bubble more (or buzz louder, or clean better) according to your observation.

    Below is a simulation of a twin-tee oscillator which is tunable from 30k to 80kHz. The potentiometer was dialed from low to high position as the simulation ran.

    Click image for larger version. 

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    If you are familiar with the 555 IC, that makes an easily tunable square-wave generator. A flip flop divides by 2 while it produces 50 percent duty cycle. You can filter it so the waveform is sine-like. You must build a circuit which drives your transducers.



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    Re: ultrasonic generators

    Quote Originally Posted by BradtheRad View Post
    It sounds as though you hope there is a circuit which performs a frequency sweep, then settles at the frequency which produces the greatest amplitude from the transducers. I'm not sure I can design a reliable analog circuit. A microcontroller might be a good controller for such a task. However it may be redundant to do the seeking action each time you turn on the cleaning machine. I don't think the frequency will change much between uses.

    Or it's probably easier to do by human evaluation. There are various tunable sine-wave generators. You can watch to see which frequency causes your gang of transducers to bubble more (or buzz louder, or clean better) according to your observation.

    Below is a simulation of a twin-tee oscillator which is tunable from 30k to 80kHz. The potentiometer was dialed from low to high position as the simulation ran.

    Click image for larger version. 

Name:	twin-tee oscillator one NPN 7V tunable 30k to 80k Hz.png 
Views:	2 
Size:	13.5 KB 
ID:	148342

    If you are familiar with the 555 IC, that makes an easily tunable square-wave generator. A flip flop divides by 2 while it produces 50 percent duty cycle. You can filter it so the waveform is sine-like. You must build a circuit which drives your transducers.
    This is what I'd like to achieve for my design: https://www.youtube.com/watch?v=IVm2m0UshVM this one does not seem to have a microcontroller for the sweep function.



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    Re: ultrasonic generators

    Hi Brad! I found this schematic on the web. Can this driver circuit work at the frequency of 130khz?Click image for larger version. 

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    Re: ultrasonic generators

    Re Youtube video: I'm unable to be sure what creates the louder buzzing, whether it's a change in frequency, or a change in applied voltage. Someone familiar with ultrasonic cleaners would have a better grasp.

    This is an area where experimentation can tell us how to gain best performance.

    Your schematic probably can do the job although the internet is notorious for having untested or impractical circuits.
    The output transformer needs to be correctly designed and constructed. It takes a lot of work, and it's hard do build a transformer right the first time. Especially since you're considering a 600W system. The schematic is complicated whether you build one or several. Perhaps it is commercial quality, however it's a project for someone with lots of experience in electronics.



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    Re: ultrasonic generators

    The schematic looks more like an experimental setup (e.g. from a last years project) than an industrial ultrasonic generator. They are basically square wave power generators, achieving the sinusoidal current by the transducer resonance or additional LC filters if required.

    Efficiency is low due to class AB power stage, operation at 130 kHz probably problematic.



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    Re: ultrasonic generators

    Quote Originally Posted by FvM View Post
    The schematic looks more like an experimental setup (e.g. from a last years project) than an industrial ultrasonic generator. They are basically square wave power generators, achieving the sinusoidal current by the transducer resonance or additional LC filters if required.

    Efficiency is low due to class AB power stage, operation at 130 kHz probably problematic.
    which schematic are you refering to?



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