Signal generator to drive Ultrasonic transducer

[Nanobubbles]

Hello Maker Pro Forum,

I'm trying to set up an ultrasonic transducer to create nanobubbles in a metal container. The first part I'm troubleshooting is trying to make sure the output is strong enough to run the ultrasonic transducer. The Ultrasonic Transducer is the BQLZR Ultrasonic Piezoelectric Transducer Speaker 28khz 100W from amazon. I have it mounted underneath my metal container. My goal is to put out a 20-25 khz 15-20 watt sin signal to drive the transducer.

The Signal generator I'm using is the Koolertron Upgraded 15MHz DDS Signal Generator Counter,High Precision Dual-Channel Arbitrary Waveform Function Generator Frequency Meter 200MSa/s (15MHz). The maximum output, in terms of wattage, is 1 watt at 20 volts.

Then using a BNC to alligator clips connector, I use a Bogen Transformer Model T725-10 10W to step up the signal. I hope I have the wiring with this transformer correct. I have it connected to the COM wire and then because I can't tell which one is the 8th tap, I have it connected to 7th wire away from the Com wire.

Then from this transformer, using alligator to banana plugs, I amplify the signal with a Hewlett Packard 465A Laboratory Amplifier. The signal is amplified by 80DB.

Finally from the amplifier to the transducer I use banana to alligator clips to run the transducer.

I have tested my set up and all I get is a high pitched sound and no movement of water in the tub. I have a video attached to this post for people to look at it to get an idea of what I mean. My question is whether I am doing this correctly and if not, where in my set up am I going wrong?

Here is a video of my setup running. Note that although it says 10 khz instead of 20-25 khz as I said above, it still makes the same sound if outputting 10khz or 20-25 khz:

IMG_2563.mp4

drive.google.com

Attached are photos of my step up transformer and wiring.

Hope I have explained it clearly, appreciate any help.

 

[Harald Kapp]

https://www.amazon.de/-/en/Frequency-Amplifier-20Hz-100KHz-Sensitive-Precise/dp/B0CFV32WHHThe transformer you use looks like a mains transformer, suitable for 50 Hz or 60 Hz. By no means will it work as expected at 10 Khz or more.

The signal is amplified by 80DB.

The manual states that the HP465A amplifier can amplify by 20 dB or 40 dB, not 80 dB. It will also output max. 1/2 W, way less than the 15 W - 20 W you expect.

1. get rid of the transformer.
2. use a power amplifier suitable for 15 W - 20 W at 10 kHz - 25 kHz. Here's an example.
3. use an inexpensive generator instead of the comparatively expensive Koolertron DDS generator. Here's an example for 8 €, here's another one, looking slightly more "professional" for 21 €.

 

[Nanobubbles]

Appreciate the response. That's the first and last time I'll consult Chat GPT on this project. It recommended me that amplifier and transformer. Hopefully I can sell the both of them to someone in my local area that needs them.

Just to clarify, I don't need a pre-amplifier if I use the recommended amplifier?

Is the recommendation to use a cheaper signal generator rather than the Koolertron due to how effective the cheaper signal generator works with your recommended amplifier or because the Koolertron is likely to be damaged during this experiment? Could I just use the Koolertron with your recommended amplifier?

 

[Harald Kapp]

Just to clarify, I don't need a pre-amplifier if I use the recommended amplifier?

Should not be required.

Is the recommendation to use a cheaper signal generator rather than the Koolertron due to how effective the cheaper signal generator works with your recommended amplifier or because the Koolertron is likely to be damaged during this experiment?

For driving the ultrasonic transducers in this application you don't need a high quality, low noise, low distortion signal. You can use the Koolertron, it should work with an amplifier as I showed as an example. Damage will, if at all, happen to the amplifier. The Koolertron is unlikely to be damaged - provided your setup is correct (no short circuits, proper grounding etc.). If you happen to have the Koolertron, there's no need to buy another generator. But if you need to buy one, you can save a lot of money by using a much less expensice generator.

 

[poor mystic]

Hi
I'm not sure why you need a sin signal. This is a capacitive device which you can pour charge into, and pour it back out. It seems to me that it would be easier to drive this device with a square wave.
Why not use a totem pole and just drive it plus and minus as hard as you can?