Hello Franc,


I found this URL for a "Model 2800: Miniature Ultrasonic Cleaner":
http://www.asiabt.net/tradeleads/def...ubCategory=235

I found the same url. In this the Karin Co. Ltd claims it produces this same
model...
I insist, don't rely to chinese specifications, claims, etc. China is a
country without copyright law at all. China is "selected" to produce
imitation procucts, that's why no copyright law. If you see specifications
saying: 50W, 42kHz, CE approval, patent no., etc, no surprise if you get:
10W, 25kHz, no CE, no patent at all... Inside China, there is no punishment
for a company if it uses CE, ETL, GS approvals signs if it has no approvals.
They can make Rolex, Lacoste, or any imitation with no fear.

The other ultrasonic with the conventional buzzer (20mm diametre, less than
1mm thick) claims 30W!!!
Now, I understand the difference with a "real" ultrasonic with two "real"
transducers I have had. Time comparison for the same cleaning results:
a. Real ultrasonic 60W : 0.5 min
b. the ultrasonic we talk (50W) : 9 min
c. the other ultrasonic with the buzzer (30W) : 25 min...


It makes no sense to say that a transducer can "resonate" at twice its
resonant frequency (unless you are talking about overtones maybe ???).

Yes, I thouhgt the second overtone.


I'm guessing that the cleaner's circuit automatically oscillates at
the transducer's resonant frequency, ie the external components aren't
that critical. I suspect that if you were to replace the transducer
with a higher frequency type, the new transducer would oscillate at
its own resonant frequency, not 42kHz. You may need to optimise some
components, though, to ensure that the transducer looks like a pure
resistance. The frequency characteristics of the ferrite toroid would
need to be considered as well.

I don't know to say if it's correct or not. I'm just thinking.
1.. The transducer (ceramic ultrasonic transduder, like a bigger buzzer) it
has a mass of say 25g. It is glued on the tank, say 100g. And the tank is
filled with water 400-600g. I wonder for its resonance frequency.
2.. Just a question because I don't know. Could someone take a conventional
small buzzer and make a circuit to work on the buzzer's resonace frequency,
relying on the buzzer's characteristics without RC or other similar parts on
the oscilator? If yes, then it is a possibility to be the same in this
machine.

I will try to find the schematic, and I will send a message.