Ultrasonic Cleaner

[Mad Professor]

Good Day All.

Sorry I post here but I don't know of any other tech forums.

I have quite a large Ultrasonic Cleaning Tank that all the plasic case has just fallen apart.

I have been thinking about building a new stainless case for it.

This unit just has a on button and it just get's on with it.

I will fully admit I don't understand the workings inside an Ultrasonic Cleaner, so please bear with me on my next few questions.

What sort of voltage is feed to the Ultrasonic Transducer?

Are the Ultrasonic Transducers a preset freq or does it have a working range.

I only ask as if it was possible to control this with a PicAxe so that I can adjust the Freq so that I can have a soft or harsh cleaning.

Thanks for your time.

 

[Andrew Cowan]

What sort of voltage is feed to the Ultrasonic Transducer?
No idea - show us a picture, and we could make a guess.

Are the Ultrasonic Transducers a preset freq or does it have a working range.
The transducer will have a range it works from (eg 39-41kHz, the cleaner will be sending it one frequency (eg 40kHz)

I only ask as if it was possible to control this with a PicAxe so that I can adjust the Freq so that I can have a soft or harsh cleaning.
I imagine changing the voltage would have more of an effect on this, although changing the frequency would be easier.

Andrew

 

[slimplynth]

Our factory uses three different ultrasonic cleaners from bench-top sized in the lab up to 3000L on a descale process line... what size are you looking at?

 

[kevrus]

I believe it is usual to vary the signal amplitude to the transducer to vary the cleaning power as apposed to the frequency as it is usual to run the piezo transducers at their resonant frequency, as Andrew says, hence it will be more like a 'volume' control and not a 'bass' or 'treble' control.

 

[Mad Professor]

Ok thanks for the quick replys so far.

I will take some pictures of the PCB in the morning.

Thanks again.

 

[Michael 2727]

I don't have an U/Sonic cleaner, I want one, but from some earlier reading I think they
operate at closer to 200kHz. A mate of mine bought one of those pond/fish-tank Fog,
Mist making devices which would be very similar to a cleaner.
The piezo element is around 50mm/2" inch diameter and driven from an epoxy blob inside
a plastic case about the same size. My best guess would be a simple Audio Amp or Oscillator
driving Transistors/MOSFETs etc. These units produce a cold vapor/fog/mist and bubble the
water as well. In Audio terms I would think they drive the element at a few Watts, a bit
(lot) beyond the output of a single 40kHZ transducer.

I have a heap of 40kHZ transducers and was thinking of making a single spot unit (not inside a tank) that used a few drops of water directly on an object, eg: a PCB.
Another thing on the to-do list,

 

[boriz]

Activate the unit and measure the frequency directly using an oscilloscope. If you can’t use a ‘scope, a PICAXE at 8MHz can measure frequencies up to 50KHz using the COUNT command. It would take 5 minutes to breadboard a PICAXE frequency counter using DEBUG to display results (remember to limit input voltages). For frequencies >50KHz, use an additional chip like a 4017 decade counter for dividing the frequency by any power of two upto 10 (2^10 = divide by 1024).

 

[BCJKiwi]

Only experience with Ultrasonics was with a plastic component welder in a volume production line.

Generally the excitation is via a piezo module directly connected to a 'Horn' - typically of Aluminium alloy. The Piezo and horn form a resonant circuit which sets up an amplified high frequency vibration in the horn which in turn provides the vibration to do the work. For the welder, vibrate the plastic parts together to produce heat by friction and the welding, or, for the cleaner, vibrate the fluid which breaks down into minuscule hot exploding bubbles.

So, in short, it is a tuned system which is why there are usually no user controls other than time to run.

 

[Michael 2727]

I found this- Frequency Used in Ultrasonic Cleaning.
http://hypertextbook.com/facts/2004/ChanMaung.shtml

I also found a reference to 26Watts for a jewelery cleaner unit.

Just a matter of finding out what power you can dump into a standard 40kHZ
transducer, not much I would think.
BTW a standard SRF type transducer are a tuned device, ie: they only operate
at 40kHZ, one or two kHZ off the mark and they don't do much at all.

 

[gengis]

Ultrasonic cleaners use rather high voltages to excite the tansducers. Our 300 watt units used something like 500+ volts peak to peak at 40 KHZ. They doubled the incoming 120 volts then used a power oscillator composed of a pair of large 60 volt filament vacuum tubes, with plate caps, and an air-core, "pie" wound, coil to drive the transducers and provide power line isolation They still make them too - even though tubes command a premium these days. The tubes were mounted horizontally below the baths and only the switched the B+ on via a timer. The tubes did heat the water so I guess it had some logic behind it.

If you look at http://www.repairfaq.org/sam/samschem.htm
Input 115 VAC output 460 VAC at 80 KHZ, Single NPN transistor operating off the mains voltage as a power oscillator.

I took apart one of the small drugstore retail jewelry type cleaners and they used an SCR in the oscillator circuit. The circuit was simplicity itself - SCR, tapped ferrite rod coil, resistor and cap on the primary and secondary winding driving the transducer. No rectification of the mains voltage.

Frequency is probably dependent on the resonant frequency of the transducer and load. Probably higher with small low capacity baths and lower with the bigger ones. Just a guess, since it appears as if they do try to tune the secondary of the transformers of the ones I've looked at.

Ever put a beer in one or carbonated beverage into one? We used them in laboratories to de-gas liquids. Freshly opened cold beer lowered into the liquid bath was really impressive.

 

[Dippy]

Mad prof,
why don't you get some Google info on the one you've got? Maybe the info is in the Opertaors Manual Specs?

Maybe if you told us the Manuf's name someone could hazard a guess.
As you can see from above there are many specs.
So, without more info people will be Googling and posting a lot of things which won't help you with your device.

I've just looked at a German made 4litre U/S cleaner (Emag). 38kHz @ 200W.
Sorry to say it, but I think driving this is well beyond the capabilities of an electronics newbie.

 

[Mad Professor]

Here is a picture of the PCB.
http://www.mad-professor.co.uk/Misc/Ultrasonic%20Cleaner%20PCB.jpg

I totaly admit I have no idea what the make / model of this cleaner as I did not keep the old broken outer plasic casing.

I probed the output of the PCB and the voltage seems to peak around 200volts.

Due to the high voltages this unit seems to use, I would say using a Picaxe to control it is out of the question.

As the unit is still working, but all the outer plasic casing is gone, I will just mate a new casing out of stainless.