building a sine wave oscillator

When you can do the math to explain how to select the light bulb, you won't have any problem designing your oscillator.

Reply to
JosephKK
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What you want is a hydrophone

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You should do a bit more research before start this project. For practical audio frequencies, the attenuation of air is uniform with frequency. My recollection is water falls off at either 6dB or 12 dB per octave. So the loss at 24KHz will be severe.

Reply to
miso

LOL, Joseph, so you caught my algebra goofup too. There is no excuse, I know, so I am not going to try and make any. I will not use a light bulb. There are other nonlinear elements I can use. I DO know the principles that the wien oscillator works by. Also, there ARE other oscillators I can use, which I am just now discovering

Thank you for pointing this out.

Joe

Reply to
Joe

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Dear M...

I already have a hydrophone. That is what I am going to use to receive the 24khz. It will receive or transmit up to 25khz, the mfr says to stay away from 25khz if transmitting, but I can receive at any frequency within its range with no problem. Been there, done that.

As far as research, you might want to do a little yourself, start here:

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The what you call 'loss' is proportional to 1/r^2, just like em waves. Because of the spherical or hemispherical nature of the wave propagating thru the water. There are also absorption losses due to the manganese dioxide present in sea water. At 20khz, this amounts to

-3dB in a kiloyard (I know, unfortunately some folks still use the imperial system). Now the 1/r^2 I am speaking of is the acoustic energy flux density (aka intensity), NOT the sound pressure level. The sound pressure level falls off as proportional to 1/r. I would refer you to a great book on this very subject: "Principles of Underwater Sound" by Robert Urick , and also "Transducers and Arrays for Underwater Sound", by Sherman and Butler. You can take a quick peek at them at amazon.

I know a little something about the physics of sound propagation in different media.

My original question was about building a sine wave oscillator, which has been answered, and I wish to thank everyone who replied. I know what I am up against as far as sending sound through the ocean. I am trying to design with those principles in mind, hence, the reason I wanted to maximize the output from my multiplier.

Electronics has been a hobby for me, so that is why I come here and ask questions on occasion. Most of the time, I just lurk and learn. Oh, and screw up algebra.

Thanks again to all who replied. I believe I can make my way from here.

Joe

Reply to
Joe

They fall as 1/N^2 instead of 1/N so the higher ones are much lower.

With an oscillator and a CD4017 and some resistors, you can make the low numbered harmonics low.

Reply to
MooseFET

Joe:

You stated a piezo transducer. That could be many things. If you said hydrophone, it would have saved some time.

I designed this kind of gear (sonobuoy) in the 80s for use with the P-3 Orion and quite frankly have no interest in digging up loss factor of the ocean for something I did two freaking decades ago. Since you have a chip on your shoulder, I'll cut this short. The loss I refer to is not that of a 1/r^2 radiator. Rather, on the receiving hydrophone, you equalize for the loss of the ocean. The filters had a rising response. This was for a passive system obviously.

Reply to
miso

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Dear M,

My apologies if I came across as having a chip on my shoulder. I just wasn't sure you understood what I was asking about.

The type of transducer I have been looking at can be seen at :

http://209.41.160.145/site/index.cfm?DSP=3DPage&ID=3D101

On the right hand side of the page there is the sx23 and the sx22.

I guess you could call it a hydrophone, but it's my way of thinking (which is not necessarily correct) that when I hear hydrophone, that's for listening. piezo transducer can be for listening or transmitting. Those are just my definitions and that is probly why I misunderstood your good intentions.

Since you were in the biz, I would summarize it by saying that I think of a piezo transmitter like a loudspeaker (or underwater sound projector), and I think of a hydrophone as the water equivalent of a microphone in air. So, I already have one that listens, now I am going to build one that transmits, and that was why I was inquiring about some ideas for a sinewave oscillator.I know most piezos can receive or send. My bad.

Again, thank you for your reply.

Joe

Reply to
Joe

mixer.http://en.wikipedia.org/wiki/Frequency_mixer

This is beginning to sound similar to an underwater "handy talkie".

Reply to
JosephKK

Not to be too picky but, that may not work well OP starts trying to modulate the signal. OP has stated this in multiple posts.

Reply to
JosephKK

Having read many more of your posts, i apologize for being unnecessarily snotty. It seems that the bulk of the group here is focusing on power transfer and ignoring the intent to modulate to carry voice or data.

Reply to
JosephKK

That, of course, depends on what form of modulation is being considered.

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Regards,

John Popelish
Reply to
John Popelish

Well, I think I understand what you are saying John. Right now I am using a function generator (sine wave) at audio frequencies to modulate my carrier. But there is no piezo transmitter on it yet either. I have built the colpitts oscillator on the breadboard from the link to hyperphysics that Joseph gave me (Thanks Joseph, BTW, I didn't think you were snotty). Amplitude modulation.

Now, though, I am thinking about, in the past when I have used the good ole 555 to modulate IR LEDs for various applications. I would actually use a 556, one half would oscillate at 38khz, and the other half would oscillate at, say 10khz. Connect the output of the 10Khz astable to the reset pin of the 38khz astable, and now I am not sure if it is the reset pin, so Let's say use 2 555's first one is oscillating at 10Khz, the second one is set to oscillate at 38Khz. I take the output from the 10khz and tie it to pin 4 ( pin 4 is connected to ground thru a 33k resistor ) of the 38Khz 555, and, presto, I can use one of those IR decoders made by sony, or whomever to get my 10khz at the receiving end. In fact, I think you were the one who told me about this method on the seb forum a few years ago. The reason I changed this over to 2 555's is because I have the pins memorized, but I did use a 556 for that app.

I am pretty sure I am going to be transmitting digital data. I may be wrong, but that's zero's and ones, and no crossing zero ?? So I guess maybe the multiplier chip I am using may not be the right one after all. Although it may be more versatile, ie, I should be able to modulate it with either analog or digital. Right now, I am modulating it with analog (linear amplitude modulation) audio across the whole audio spectrum. With digital, I should probably only need a bandwidth of 5khz or so. So if the data is strictly digital, then I should be able to use the 555 (or 556) the same way and not even worry about a sine wave?

er, something tells me we've come full circle here, because you told me that in one of your first posts.

I guess maybe I should just try it and see what happens.

Joe

Reply to
Joe

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