Don Foreman -- ultrasonic transducer

There are some schematics on Branson's website. See, e.g.,

I have a hunch (but don't know for a fact) that L1 and/or T2 in the referenced schematic may be square-loop inductors. I have some small squareloop toroids if you want a couple. You'd need to strip them and wind them with what is needed. The MOSFET's cited are obsolete, no problem. Pick any 400-volt several-amp TO-220 MOSFET, there are many good choices at Digi-Key for a buck or two, or I could send you a coupla those as well.

I don't have any ideas for SS tanks other than see what you can scrounge as surplus medical or thin kitchenware. I don't think there's anything critical other than thin is good. Ya might find a good thin SS tank in a discarded deep fryer.

I found the "magic epoxy" at a local distributor -- for 50 bux a tube. I've somehow managed to contain my enthusiasm for grabbing a tube. A single 70W 'ducer probably won't have a lot more moxie than the $49 HF unit. Larger cleaners use several 'ducers.

I haven't played with my xdcr yet other than just fooling at the elex bench. May not get around to that for a while. Truth be told, the HF unit is working fine for me. I wanted the 'ducer for other experiments, as perhaps coupling ultrasound directly into a liquid-filled fouled firearm barrel with some sort of matching horn.

Don, how big of a tank can I use with this transducer. (not sure how big is your HF tank)

Also, I have a fundamental question. What if I simply build a variable frequency, variable power oscillator circuit with a big amplifier. I could even attach an amplifier to a wavetek that I have. Then I could carefully select proper resonant frequency that matches this transducer.

Which I think is easy with some ICs, a little trim pot and a darlington of one sort or another.

Would that not be enough to make this transducer make ultrasound noise?

What am I missing here? I looked at that schematic. Did not really understand what it does, specifically why there is a second transformer with two primaries.

thanks

i

Don, I found something interesting that explains why there is a second transformer.

Chapter 14) Ultrasonic cleaner schematic

Ultrasonic cleaning is a means of removing dirt and surface contamination from intricate and/or delicate parts using powerful high frequency sound waves in a liquid (water/detergent/solvent) bath.

An ultrasonic cleaner contains a power oscillator driving a large piezoelectric transducer under the cleaning tank. Depending on capacity, these can be quite massive.

A typical circuit is shown below. This is from a Branson Model 41-4000 which is typical of a small consumer grade unit.

R1 D1 H o------/\/\-------|>|----------+ 1, 1/2 W EDA456 | C1 D2 | +----||----+----|>|-----+ | .1 uF | EDA456 | 2 | 200 V | +-----+---+ T1 +---+------->>------+ | R2 | _|_ C2 )|| o 4 | | | +---/\/\---+ --- .8 uF D )|| +----+ | | | 22K _|_ 200 V )||( + | | 1 W - 1 o )||( )|| _|_ +-----------------+---------+ ||( O )|| L1 _x_ PT1 | R3 | 7 ||( )|| | | +---/\/\---+ +-----+ ||( 5 + | C \| | 10K, 1 W | F )|| +---+ | | Q1 |--+-+--------------+ 6 o )|| | | | E /| | D3 R4 +---+ +----+------->>------+ | +--|

The HF tank is about 6-5/8 x 5-3/8 x 2-5/8 deep.

That'd work, but tuning would be fussy. The Q of these xdcrs is about

1000, so the 3dB bandwidth is about 40 Hz at around 40 KHz. It might be tricky to adjust a Wavetek to that degree of precision and stability. My Wavetek wanders about 20 Hz when set as close to 40,000.0 Hz as I can get it.

Possibly, if your oscillator is stable enough and at the right freq.

If you refer to TX2, that's a gate drive current xfmr with two secondaries, driving the MOSFET half-bridge. Circulating current in the resonant load will "pull" the oscillator into some semblence of synchronism.

There ya go! Steminc has confirmed that these transducers can take up to 2KV if properly matched to the load. They suggested using a bit more liquid than "normal".

If/when I get motivated to work with my 'ducer I'll post my wanderings and flagellations. At the moment, however, this project is not on my priority list. It does appear to be on yours, so lead on!

I see. That makes sense.

Well, I suppose that there are plenty of stable oscillator chips out there.

Thanks Don. I am beginning to understand better.

What size tank, you think, would be the biggest tank that could work with a 70W transducer?

i

I don't know. There may be some minimum power density for cavitation, but I don't know how much ultrasound disperses laterally in a liquid. It probably is related to the ducer lateral dimensions in wavelengths. Some fishing and depthfinder sonars (higher freq) have fairly narrow cones.

Tank size may not make much difference if the ultrasound tends to be mostly in a cone above the 'ducer -- though little or no cleaning would occur in regions away from the cone. Larger cleaners have multiple transducers.

Cleaners seem to have a recommended range of depths. That may have something to do with standing waves in the vertical column of liquid.

I will try to use this bucket:

it is 12" diameter on top.

i

I don't think that this will work, even if one is willing to ride the controls, because the resonant frequency of the transducer will vary with temperature, which will be rising because of the high power being applied. Temp will eventually more or less stabilize, but it will never be constant enough. This is why such transducer drivers use the transducer itself to set the frequency.

Joe Gwinn

As a point of comparison, the Branson tsnks that I'm familiar with in this size range use 12 xducers and 500W power supplies.

Ned Simmons

...

That is an impressive ASCII drawing! That took either a helluva lot of patience, or an ASCII CAD app. I wonder if there are any ASCII drawing app's? Bob