How to make and control ultrasound frequency

I'm a beginner at arduino. For a project I want to create standing ultrasound waves and be able to change the frequency. The circuit also has to be waterproof.
I have these two items JSN-SR04T Ultrasonic Distance Measuring Sensor - Waterproof and Weather-proof Ultrasonic Sensor (SEN0207).

you need to investigate ultrasonic transducers, the devices that generate ultrasonic energy for cleaning devices. they are not chump change cheap.

1 Like

People usually use the timers that are present in most microcontrollers. The details vary, so look for tutorials specific to the Arduino you plan to use.

I have different parts as you can see

If you substitute parts, they may not work as in the tutorial.

1 Like

Thank you. So, even though the ultrasonic transmitter is supposed to only do 40kHz, I can change it through arduino programming to something like 20kHz?

No, the sound is produced by a piezo that is resonant at the frequency. IF you really want to produce sound frequencies over such a broad range, look for "tweeter" type speakers that can reproduce the frequencies you want, and then build/but amplifiers that can drive such speakers.
Paul

1 Like

Thank you so much Paul! Do you have any certain tweeters that you recommend and can they be waterproof?

No, never had a need for either. I am sure you can do an on-line search as well as I can. What is the point of waterproofing? That would destroy the frequency response range.
Paul

1 Like

Ok. Thank you so much for informing me. I'm trying to create standing ultrasound waves underwater to flocculate algae, so that's why I was looking for something waterproof

You will need many, many watts of audio power to apply much sound energy to water, no matter the frequency.
Paul

1 Like

Paul is correct. Energizing a piezo at its resonant frequency will have much higher "gain" than off frequency. However off frequency will work.

When you say "waterproof" are you submerging the sensor in water? If so the resonant will likely shift due to the coupling of the water to the sensor.

What range of ultrasonic frequencies are you interested in?

1 Like

The 40 kHz generator is internal to the ultrasonic range finder. To use a different frequency you will need to bypass the built-in frequency source and substitute a signal from your Arduino. It looks like the Levitator just uses an H-Bridge DC motor driver to drive the transducers directly.

I am interested in 20-22kHz. Thank you for your response :slight_smile:

What do you mean by substitute a signal from your arduino? (Iā€™m a beginner to this)

I can't imagine any piezo sensor capable of 20 to 20kHz. I can't even imagine a speaker working over that range.

I will assume, that unless you provide more insight to your goals I cannot be of any help.

1 Like

You will need a high power ultrasonic transducer designed to work efficiently in or in contact with water, such as the ones designed for ultrasonic cleaning baths. The ones designed to work in air will not couple energy efficiently to water.

While looking, check the frequency range of the transducer.

2 Likes

For a test, put the transducer in a plastic box that is waterproof and put the box in the water.
Paul

1 Like

My goal is to use ultrasound to get rid of algae in a pond

Assuming you mean 20kHZ to 22kHZ what makes you think that is ultrasonic?
While it is beyond my hearing, my son who is in his late 30s can still here that.

Also any wild life in the pond will be disturbed and possibly injured by such a strong signal.

The way to remove algae is with a UV light, pump and filter.

1 Like

You're supposed to tell us this up-front so we don't recommend inappropriate devices - the acoustic impedance of water and air is incredibly different (4 or 5 orders of magnitude IIRC), they need completely different transducers.

You are looking for a wideband ultrasonic hydrophone. These terms may help in a search.

1 Like

Here is a commercial system you can emulate. It sweeps from 10 kHz to 34 kHz and draws 8 Watts.

(Only $4,173.00!)