Yesterday I wanted to do a DIY ultrasonic cleaner, but I've never heard of a transducer before: Tutorials/articles?

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
I've no idea how a transducer works. Searching here turns up a lot of stuff. I'm overwhelmed and can't find an introductory article or tutorials. Ideas?
Thanks!
 

SamR

Joined Mar 19, 2019
2,783
A transducer converts energy from one form into another.
Microphone converts sound waves into electrical energy. Ultrasonic transducer converts electrical energy into Ultrasonic Sound energy.

Very basically.
 

pmd34

Joined Feb 22, 2014
518
The tranducers are based on a piezo electric material. When you squash /flex the material it generates a high voltage (but low current) - like some of the cigarette lighter / gas cooker starkers. Conversely, when you apply a high voltage the material expands or contracts.
To get a "large" movement (<1mm) from the material you typically get a piezo stack with many piezo elements electrically connected together in parallel, to reduce the over all voltage.
The properties of the piezo change with frequency and they have a natural resonance. For positioning of things with a piezo you can simply apply a voltage to them, but they have a hysteresis so when the voltage is dropping again the material is a different size from when they voltage is increasing.
For ultrasonic cleaners, the most common way of running them is to make use of the natural resonance of the transducer, a step up transformer is also commonly used to get the optimal voltage for the transducer. Be warned that the transducer behaves a bit like a capacitor and retains the high voltage after power off!

https://www.apexanalog.com/resources/articles/PET-Final-PUBLISHED-Article-4.06.pdf
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
@shortbus I read/watched a few reviews on the popular US cleaners on ebay. They are not up to spec. That is to say, they advertise one thing and deliver another (your selection is in this category). They also tend to be exceptionally small.
No need to worry. I'll learn. I'll design. I'll build. I'll electrocute myself. It'll explode. And I'll go to heaven. ;)
 

SamR

Joined Mar 19, 2019
2,783
Ultrasonic cleaners have to be small to be effective/efficient. I would also use a non-soap detergent additive ala Alconox which has a wide selection of Lab grade cleaners. Effective ultrasonics will heat the water due to energy transfer. I've never known one to boil but they can get hot. This is not a bad thing unless what is being cleaned has a low melting point. For larger parts, there is steam cleaning/pressure washing...
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
Thanks, @SamR that fills in a blank spot. I wanted one that was about 3-4 gallons in capacity, so not huge and not small.

Here are a few unanswered questions on the subject. I'll repost one if it gets buried.
1. So if these transducers are modeled as capacitors, how is it that they are referred to in watts? As in: 20W transducer, 50W transducer. And if they do consume some wattage, how do you calculate the resistance so you can determine the amps? Or perhaps this is included in a datasheet I don't have...
2. How do you test one once you have it. I mean to check the input power (measuring capacitance at high voltages is difficult from what I know), the output power (I'll need to physically measure it)? The resonance frequency can be read by a microphone and oscilloscope.
3. What's the power to water ratio? As in, if I want a tub X size I'll need Y power of a transducer.
 

Tonyr1084

Joined Sep 24, 2015
5,220
I used to use an ultrasonic jewelry cleaner. Interesting device. Working in the electronics industry I used it to clean many small items. I even used it to clean inspectors red stamps. A rubber shape indicating whether a part has been inspected, accepted, rejected or final accepted. Over time those stamps build up debris and can get blurry. Most people would take a wooden cue tip and alcohol to clean it. I messed with the cleaner and noticed that when I put the stamps into the water (no chemicals) the stamp would not get cleaned unless the rubber stamp was at a precise location in the water, center, about 25 mm above the bottom. As I lowered the stamp into the water I'd watch for a reaction. When it hit that point the ink and debris would literally blow off the surface in a puff of red ink. So I stuck my finger in the water to see what was going on at that point. I could feel the energy of the waves of ultrasonic energy striking my finger. A little lower and those waves of energy would hit my finger bone. And it would be somewhat painful.

The point of this is that USC's are somewhat like microwave ovens in that they have waves that bounce around. Some of those waves cancel out each other and others amplify the energy. There was also a very large USC unit, had to be around 10 gallons (guessing from memory). I believe that unit had several US Transducers (emitters) at the bottom of the tank. That sucker was powerful. One assembler put a board in the USC and went to break. When she came back - all leaded components had been washed off the board. The energy was so great that it fatigued the leads to the breaking point. It was meant to be used for a very short period of time, not 15 minutes or more.

A crystal, which is what is at the heart of the US transducer can be thought of as a wafer, or a disk. When energized with a positive on one side and negative on the other side, it deforms, like a dome. When pos and neg are reversed it changes shape and becomes a bowl. If charged in either direction it tends to hold that shape until the leads are shorted. Then it becomes a flat disk again. Depending on the size of the transducer it will have a resonant frequency; one where it moves the most in its most natural form. It's like a spring. Snap it and it vibrates at its natural rate. Try to make it vibrate in a faster or slower frequency and it will not move as much. It will move the most at its resonant frequency.
 

Reloadron

Joined Jan 15, 2015
5,667
I've no idea how a transducer works. Searching here turns up a lot of stuff. I'm overwhelmed and can't find an introductory article or tutorials. Ideas?
Thanks!
If you know what a speaker does you should know what a transducer does.
"What does transducer mean?
A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. ... The process of converting one form of energy to another is known as transduction".

Taken from the Wiki definitions.

Ron
 
On the "to do" list, I was able to acquire an ultrasonic that, as usual, blew up all of its parts, so at least I ave a non-heated tank.

I bought the guts, but never took the project to completion.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
@ericgibbs I know about the "palm sander as ultrasonic cleaner" trick. It doesn't seem to work well based on my research.
The professional 15L dual frequency cleaner costs $402 before shipping. I quoted my own transducers and container at $68 including shipping and that's without me trying to do combined shipping which could lower the price by $20.
 

Reloadron

Joined Jan 15, 2015
5,667
So that means anything between 100 and 240 volts at the resonate frequency, or that if you connect one of their power supplies then it needs 100V~130V or 220V~240V AC?
I believe it's the latter as in their power supplies designed for 100 to 130 VAC or 220 to 240 VAC. They really don't say much.

Ron
 

shortbus

Joined Sep 30, 2009
8,044
https://www.bjultrasonic.com/shop/40khz-60w-ultrasonic-cleaning-transducer-pzt4/ here are some specs on the transducer. It reads: Input: 100V~130V or 220V~240V AC.
So that means anything between 100 and 240 volts at the resonate frequency, or that if you connect one of their power supplies then it needs 100V~130V or 220V~240V AC?
This leaves more questions unanswered then it solves.
You say the one I linked to doesn't work, so right off the bat you go to where my link is made? The transducer is only a part of this, then you need the ultrasonic power supply/amplifier.

https://ultrasonic-cleaners.org/building-a-diy-ultrasonic-cleaner.html While it looks like an add, read the text.
 
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