I would like to create a device that would produce ultrasonic sounds at a number of frequencies between 50kHz and 120kHz. I don't need any return capability, I just need to generate the frequencies and output them to a waterproof speaker (or transducer). I have found ideas for several devices but just at 40kHz. Does anyone have an idea on where to start?
Thanks,
Harry - Orlando, FL
What were you thinking of using as a transducer?
Generating the frequency is probably the easiest part.
I am trying to introduce the different frequencies into a solid surface. I believe I will need some type of transducer attached to the surface to accomplish it. I may be thinking too simply, but the transducer would act like a speaker, correct? Do you need a transducer somehow tuned to a specific frequency, or do they act like a normal audio speaker and reproduce whatever frequency you send to it?
Thanks, Harry
The transducer needs to be designed to operate within the needed range of frequencies. Audio speakers only reproduce what they are sent within a certain range. Send 120kHz to an audio speaker, and if anything comes out at all, it will be with very poor efficiency.
start by buying a flat piezo transducer (readily available in electronics retailers such as tandy, radio shack etc) and bond it to your matrix using epoxy adhesive. If it's going to work or not, you'll soon find out. Experimentation is a good way to learn.
http://www.maplin.co.uk/piezo-transducers-3202
If you look at issue 274 of the Australian Silicon Chip magazine, there is a project for an ultrasonic antifouling device for boats.
I have built one of these, and the transducer is actually resonant at 40 Khz, but they pulse frequencies of between 19 and 45 Khz into it.
I have no idea if it works, but as it gets near the resonant frequency there is a noise and ripples on the water surface ( I had the transducer against the side of a bowl of water )