Naked Science Forum
Non Life Sciences => Technology => Topic started by: homebrewer on 16/11/2013 12:06:36
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Dear Forum,
I am building a dual frequency ultrasonic generator and need some help
to design a variable inductor to individually tune either of the attached
sonotrodes .
Specification :
Tunable inductor :
Inductance : 100 mH
Tunable range : 50 to 100 mH
Resonance Frequencies : either 20 or 40 kHz
Current : 3 Amps
Voltage : 40 volts p.p.
Wire size : 0.5 mm dia
As you probably gather this is an intermediate coil before the LOPT
which I use to drive the sonotrodes.
Your comments are much appreciated.
Thanking you.
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Inductance : 100 mH
Tunable range : 50 to 100 mH
Current : 3 Amps
Voltage : 40 volts p.p.
A 50 microHenry inductor capable of 8A is about the size of a thumb. (http://www.ebay.com/itm/5pc-Vishay-Dale-IH-5-50uH-8A-Noise-Filter-Inductor-Coil-High-Current-Ferrite-/121148824235)
So a 100 milliHenry capable of 3A will be about the size of a fist, and cost an arm and a leg.
Maybe a (salvaged) mains step-down transformer with windings capable of 3A 40V would suffice as an large inductor.
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I've seen used variable transformers that weren't that expensive.
Could one be converted into a large variable inductor?
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Thanking you so much for your contribution.
One of the things I had not mentioned was the requirement for a long term
frequency stability of the circuit, taking into accounts the heat generated
by the tuning coils and the sonotrodes which impose a substantial drift
to the operating parameters of the circuit.
So I am looking for variable inductor - linked to a stepper motor and
an automatic tuning circuit to enhance the frequency stability.
I have taken note of the comments made as to the cost of the inductor and will
reduce the inductance to 25 mh and the current to 250 mA.
Once I have made a coil former next week, I will ask SOWTER to wind a couple
of inductors for testing.
Thank you for your kind contribution.
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Ultrasonic cleaners are available new on ebay for as little as £20 for cleaning jewelery / dentures,
or industrial 120Watt types costing about £100 ... http://www.ebay.co.uk/itm/Professional-Ultrasonic-Cleaner-3L-with-heating-Free-ss-basket-and-cover-/280832408592
Resonance Frequencies : either 20 or 40 kHz
20KHz may be audible by some young people , see ... http://www.compoundsecurity.co.uk/security-information/mosquito-devices [ which use 18.6KHz ]
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Thank you RD for your comments, but my application involves ultrasonic machining of very small structures.
Please take a look at this link : www.r-s-ultraschall.com
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Thank you RD for your comments, but my application involves ultrasonic machining of very small structures.
Please take a look at this link : www.r-s-ultraschall.com
My German isn't so gut ... http://translate.google.com/translate?sl=auto&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.r-s-ultraschall.com%2F
If you need circuitry which can deliver 120Watts of ultrasound at 40KHz , the industrial cleaning tank I mentioned in my previous post allegedly has that , the company you linked to also makes 300Watt versions (http://www.r-s-ultraschall.com/ma3_2_01.htm) , [ sometimes using the innards of a bulk manufactured item is cheaper than having something similar custom made ].
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I am sorry, but my German friend is just re-working his website.
Here is a link in English, very impressive portfolio of work:
http://www.r-s-ultraschall.com/pdf/samples_e.pdf