Generating True UltraSonic sound! ( need help )

Gremlin5205

hello, Im new to the world of stamps, and not to familer with the other things that might be avalible. I am trying to get my hands on a stamp that will

1. allow me to genorate several db ( decibles ) of ultrasonic sound.
2. able to be controlled through visual basic ( the programming lang. )

if you can help let me know.

thanks,

Tim

Gizmo5205@pacbell.net

Mike Green

Important details:
1) What kind of frequency range are you talking about? What kind of beam of ultrasound are you talking about? Most transducers are directional
and have different beam widths. Any ideas about what transducers you would use?
2) The Stamp is limited in how much power it can switch. Typically, it switches between 0 and +5V with a current up to about 20ma. That's about
100mw of power. A Stamp can control a transistor or other external switch that can switch more power. Essentially, the Stamp can generate
a pulse train at a frequency up into the ultrasound range. It can use the FREQOUT command to generate a sine wave up into the ultrasonic range.
The BS2 and BS2p can generate this up to 32KHz. The BS2sx and the BS2p series can generate this up to 50KHz (approx.) and some models can
go well over this. To drive a transducer using this, you'll need some kind of amplifier for any significant amount of power.
3) A Stamp can communicate using standard serial communications. It can interface to many PC's directly via their serial COM ports or via a USB
to serial adapter. The PBasic manual goes into some significan detail in the sections on the DEBUG, DEBUGIN, SEROUT, and SERIN commands.
You will need to be able to do Visual Basic programming to the extent of sending and receiving serial data via a PC COM port.

Gremlin5205

Tim:

hello Mike,

Im not sure what I need. I do know that the UltraSonic sound genorator must cover the entire room, non directional, and must be above or below·the range of human hearing. Im not sure what kind of stamp or other components I would need. The effect I am trying to genorate is to viberate a crystal or tuning fork any where in the room useing ultra sonic sound, like baby ultrasound. Then braudcast that sound in rapid bursts, morse code for example.Then have it picked up by a tuning fork or crystal. I thought I could go out and buy the audio equipment· to do much the same thing, but It might cost less to have something built to do just this one task. what do u think?

Another question, are there people here to hire to build a project like that? If so could you point me in the right direction.

Thanks for your input.

Tim

Gizmo5205@pacbell.net

allanlane5

Humans tend to sense high-frequencies as being directional, where low-freqencies are less so. This is why you don't need two sub-woofers on a stereo. I don't know if this is part of the nature of the frequencies or human hearing, though.

"Ultrasonic" tends to imply "above 20 Khz", where I'd use "sub-sonic" for lower than 20 Hz. 20 Hz to 20 KHz being the rule-of-thumb range of human hearing.

If you're trying to get something to resonate -- that may require a lot of power turned into sound. If you have something that has a 'resonant frequency' (like a tuning fork) it may require less power at that frequency to get it to resonate.

And most off-the-shelf sound equipment IS engineered for that 20 Hz to 20 Khz range, and works pretty hard to filter "noise" above and below that range, so that might be difficult too.

It occurs to me that sending an IR signal modulated with 38,500 hz, and having a detector pick up that frequency is very similar to what you're trying to do with sound. And you have less chance of deafening yourself with IR-light. And it takes less power. Would that do?

John R.

I would also mention that some peoples hearing (mine for example) on the near ultrasonic frequencies. For example we had 20kHz "ultrasonic" welders (I think the actual frequencies were between 22 and 27 kHz). I couldn't stand to be near them more than a few minutes, or I would have a splitting headache. Everyone else stood around, laughed a little, and called me "Mr. Dog Ears" (in good nature). If exposed long enough (this was a development project I was leading up), I would get physically sick to my stomach. Higher frequencies weren't a problem (we have 40 kHz welders that were not a problem.

The point being to choose your frequency carefully

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John R.

8 + 8 = 10

Mike Green

Tim,
You're way out of my league in terms of your needs. I think you're talking about specialized equipment, transducers, etc. This is not a Stamp project (although it could use a Stamp for control purposes) because the issues really are about generating the actual ultrasonic power and coupling it to the air, then designing something for the other end that would resonate with the sound involved. If you could have powered circuitry at the other end, then you're talking about something that could be done with a Stamp since you could use something like a modified PING at each end with one PING transmitting and the other PING having its transmitter disabled. There was an article in Nuts and Volts about 5 years ago on making your own distance sensor. You could probably get the back issue for details on the circuitry they used. Again, you could split the functionality with the transmitter on one end and the receiver at the other.
Mike

latigerlilly

Gremlin5205,

I have tried to do exactly what you are trying to do. Refer to my post about Rife equipment:
http://forums.parallax.com/forums/default.aspx?f=5&p=1&m=154833

The problem with using the Stamp 2 as an ultrasonic signal generator is two fold;

1. The Stamp II is not capable of ultrasonic signal generation because of the limiting factor of the speed of the microcontroller. The fastest signal it can produce is equal to the fastest speed that microcontroller is capable of. The processor has a maximum speed of 20 mHz or 2000 instructions per second. That is the limit.

2. The Stamp II is not capable of partial frequencies. It can use a freqout command to generate frequencies, but the frequencies have to be whole numbers. For example, it can be 1000 mHz, but not 1020.5 mHz.

I never say that something cannot be done (the word "impossible" is NOT in my vocabulary), so I'll say it will be very difficult to achieve. Perhaps you can use the Stamp II to control the excitation of crystals that can resonate at specific frequencies that you need....

BTW, if you figure out how to do this, PLEASE let me know.... Ultrasonic frequencies are much more effective than sonic frequencies when it comes to resonating cancer cells. Nuclear Magnetic Resonance is in the mHz range.... If you figure this one out, I would really like to know how. Thanks.

Good luck,
Lilly.

Gremlin5205

Thank you all for your help. I will let you know how it turns out.

I regards to the question about useing the pinger to go to another, in the same light the IR to IR.

One of the objectives is to make a reciever that uses no power and no electronics.

For a good read, I have been trying to find a device that I saw on the history channel. It was used to bug the CIA directors office in 1950.

it was composed of a metel bar with a cone share welded to the end. ( it looked like a pipe ) " _____V " <--- like this.

the way it worked was useing radio freq braudcast out side the office. When there were people in the room the cone shape acted like a stethascope. The cone viberated and in turn vibrated the bar it was welded to. The bar interfered with the freq being genorated outside the building. The russians could pick up the difference and listen to what was going on inside the CIA directors office. Aside from the prev use, it would be neat to make a 2 way comunication device that used no power.

again thanks for the advice.

Tim

Obliow

I don't know if this is part of the nature of the frequencies or human hearing, though.

Actually it is both. A given frequency and velocity determines the wavelength (longer for low freq) of the source signal, and the spacing of the two antenna elements (ears) allow the receiver (brain) to determine direction based on phase difference. At some point as the frequency is lowered the phase difference to an offset source is not discernable by the brain.

Post Edited (Obliow) : 1/24/2007 6:40:43 PM GMT

allanlane5

RFID works this way -- the RFID 'tag' gets its power from the RFID 'reader', then 'modulates' the RFID 'idle' signal to send back the RFID 'tag's value to the reader.

HOWEVER -- this only works over a short range of distances. What the Russians did probably used a transmitter with quite a lot of power. I'm not sure this is safe.

Short answer -- There is no such thing as a free lunch. Meaning, communication takes some power. If the 'transmitter' is sending as well as powering the reciever, that takes more power (sometimes MUCH more power) than making a transmitter alone.

Note you CAN make a zero-power AM radio with a diode and a tuneable coil of wire -- though the sound volume won't be loud. Bottom line -- while what you're trying to do may sound cool, it can be quite dangerous to do it wrong. Pick some other starting project.

AIman

FYI - One of my projects required sonar in the range of 35 feet +

It is virtually impossible to change a sonar unit enough to upgrade beyond the original specs and those who try to upgrade the distance or output usually end up getting unsatisfactory results.

It would be much easier for you to look at something like the Senscomp 6500 or a weather proof sonar used in drive throughs at Burger King or McDonalds. You have to poke around the web a while to find the more powerful sonar units but they are out there.

jhoyoza

Perhaps these items may be of some interest to you?


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cheers