DIY Ultrasonic bath?

[boiss]

Given that Old PP9 batteries appear a bit thin on the ground and mine won't be flat for about a year, i was wondering if I could use my wireless charger to power a small ultrasonic bath for cleaning jewelry watch bracelets etc when the radio is not being charged. Power out put is around 5 W at 30KHz but how to transform this into agitated water etc?
Mike

[Refugee]

Mine uses a ceramic transducer that looks like a giant red Polo mint four inches across.
There is a fair bit of power there too.

[boiss]

that looks rather juicy with a nice bottle too. However I see from a watch forum that they cost about 40$US so I don't reckon they've got valves etc for that price.

[Refugee]

The modern ones just have a FET in them. Mine comes from the early 1970s and was made in the US.
There is no 240V setting just 220V. The heater gets a little bit bright so it needs a bucking transformer fitted.

[dennishoy]

I made a mistake in buying a duff one to fix using new transducers. Although these were available, the company said they were individually 'tuned' to resonate with the circuit board. Also, they were fixed using some high temperature polymer and Araldite would be no use. True or not..... I don't know, but the firm in Cardiff was very helpful.

[Refugee]

Mine works well as long as you are careful with the voltage.

[Nick]

Given that Old PP9 batteries appear a bit thin on the ground and mine won't be flat for about a year, i was wondering if I could use my wireless charger to power a small ultrasonic bath for cleaning jewelry watch bracelets etc when the radio is not being charged. Power out put is around 5 W at 30KHz but how to transform this into agitated water etc?

A decent tank is about 25W/litre, i.e. my 4lt tank has 2 x 50W transducers welded to it... its a UD100SH-4L - common as muck on eBay

Circuit is not too complex - no exotics there but there are a couple of xfrms - seems to be a basic oscillator (40kHz) with control stuff (timer, temperature settings etc.) + PP driver for each transducer and a relay to turn on/off the heater.

You can buy the transducers on their own from eBay, e.g. http://www.ebay.co.uk/itm/150607443329 or the complete board + transducer as a package, e.g. http://www.ebay.co.uk/itm/160754562847 - the board looks pretty basic - not as nice as the EUmax UD100SH one... - there may be cheaper versions out there but I haven't looked...

[Refugee]

They are pretty simple little machines.
One pentode 6DQ6B two resistors and three capacitors. The American valve is in reality a tube in its homeland. It is wired to be self rectifying and also has a steel clip that locks onto the Bakelite base that has to be pressed in order to release the valve from the holder. There is a date code that looks like 1970 to me.

[Yorkie]

s far back as the early 1980s looked into building an ultrasonic bath and still have a copy of an article which appeared in Everyday Electronics back in 1981. I saw it being demonstrated at a 'hobby electronics' exhibition in the days that there were such things. It only had a small bath - about as large as you could put a watch or a few coins in. The firm that supplied the transducer and other bits (coils and transformers) went out of business when their factory burnt down.

That was in pre-internet days so you couldn't just goggle 'ultrasonic transducers' to find out where they could be bought from. I had thought I might try to make a go of it, but it also used a couple of obscure looking coils with no details of their inductance etc. I assume that they were the 40kHz oscillator, then the resultant frequency was amplified to excite the transducer.

I'm surprised that EPE, (or more likely, 'Silicon Chip' - the innovative magazine from down-under, where most EPE articles seem to emanate from these days), haven't published a design for one. S.C. did run a project for which Jaycar list a kit for an ultrasonic anti-fouling device for boat hulls. (Seems a bit of a tall order for a relatively small amount of ultrasonic power to vibrate a boat hull sufficiently to annoy and deter barnacles!).

In recent years I've tried the 'joke' ultrasonic baths sold by discount stores, Maplin etc. Low amplitude and cut off on a timer after 3 mins, presumably because they're so inadequately designed that the transformer or whatever risks being overheated. I bought two in succession - one from Lidl, one from Maplin. They're having a laugh, surely? Neither made any impression whatsoever - soap and water would be just as effective for small tasks, so both went back the same day for a refund.

Having watched a video of a 'proper' small commercial/industrial bath being used to clean a dismantled carburettor and been impressed by it, I bought one (a Christmas present to myself in 2010!) from Allendale Electronics who do a whole range in various capacities. The one that I bought has a 2 Litre tank, is 70 Watts, has a thermostatic adjustable heater, a timer for up to 80 minutes, and a digital display. It cost £102 inc VAT, and though it's a lot to pay for something used only occasionally, as ultrasonic baths go, it's excellent value for money, given that a 50 Watt transducer and board alone from Hong Kong costs £46.99. Vat free of course if it comes 'under the radar and you don't get clobbered!

I started a thread last year, which ran its distance and can be found here:

http://golbornevintageradio.co.uk/forum/...p?tid=2124&highlight=Ultrasonic

The bath that I bought which 'tickled my fancy' is presently shown as 'out of stock' at Allendale:

http://www.allendale-ultrasonics.co.uk/u...acity.html

[Nick]

http://www.allendale-ultrasonics.co.uk/u...acity.html

That's actually a re-badged Eumax unit with a different tag (white-labelled) - http://www.eumax-cleaner.com/en/pro_show.asp?id=27 - same make as mine, but different model - lower volume & power - Eumax make a huge range of small units.

Good units - made to a not-too-tight budget - steel is reasonably thick and they are very noisy (as you would expect) - I run mine in the utility room as anywhere else in the house it gets really irritating....

I have had several of these over the years - one problem that occasionally besets them is the sticky pads that they used to use to hold the PCB(s) to the chassis - these were replaced in later models by screw-fixed pillars.

My "stick-on-keypad" (the front panel) failed after about 4 years and was not repairable, but a new one from the European importer in Germany was only 22euros delivered.

Most of the electronics is user-serviceable, except the control PCB which is uP-based and would need a replacement if anything too serious happened to it (unlikely).

The driver PCB handles the mains input, heater switching and the driver for one 50W transducer; a smaller & simpler slave board is used for each subsequent transducer.

My summary of these units and what to use in them (plus some example photos) is at http://golbornevintageradio.org/forum/sh...5#pid28945