Connect with us

Sine wave generators

Discussion in 'Electronic Basics' started by Roger Dewhurst, Mar 31, 2007.

Scroll to continue with content
  1. What is now the easiest way to go for sine wave oscillators to work on fixed
    frequencies near the middle of the audio spectrum? Are there off-the-shelf
    chips that will do the jobs?

    R
     
  2. Why would you want an IC? YOu can't get much simpler than ann audio sinewave
    oscillator, and the bulk of the components will be passive, to determine
    the frequency.

    You'll find that most of the audio generator ICs will generate a sinewave
    through indirect means, ie they start with a triangle and then distort
    the waveform till it's a reasonable sinewave. That sort of thing is
    great when you want multiple waveforms out of the oscillator, and when you
    want a wide-range oscillator since a good sinewave oscillator will
    tend to be cumbersome to vary in frequency since multiple components
    will need varying. But what's good for one thing isn't good for others,
    and the sinewaves that come out of such arrangements tend to be less
    than perfect. If you need a single frequency sinewave, or at the most
    a few frequencies, likely you want the sinewave for some specific
    use, and you want that sinewave to be fairly pure.

    A single transistor and a phase shift network will make a nice
    sinewave oscillator if you only need a single frequency. If you
    need more than one, but still just fixed frequencies, use a few
    transistors and make separate oscillators; it's easier to switch
    power to each device than switch the frequency determining elements.

    Wien bridge oscillators are the cat's meow for sinewave oscillators,
    and they were made with single tubes in the old days. An op-amp
    tends to be the active device these days, and again, for a few fixed
    frequencies it may be easiest to just build a few oscillators.

    Michael
     
  3. Phil Allison

    Phil Allison Guest

    "Roger Dewhurst" <>


    ** Kiwi Groper Alert

    ** The easiest way is to make a square wave oscillator first ( 555 or
    op-amp) and follow that with a sharp, low pass filter to remove the
    harmonics at 3, 5, 7, 9 ... times the fundamental.

    Eg:

    http://www.national.com/nationaledge/jun04/article.html

    A trim pot will permit small ( +/- 10% ) frequency adjustments.

    Add an extra RC filter at the output for lower THD.




    ....... Phil
     
  4. Bill Bowden

    Bill Bowden Guest


    You can use a dual opamp for reasonable low frequency sinewave
    oscillators.

    See my example at:

    http://ourworld.compuserve.com/homepages/Bill_Bowden/page8.htm#phase.gif

    -Bill
     
  5. Radium

    Radium Guest

    I am looking for a sine-wave tone generator that can emit pure sine-
    waves at ultrasonic frequencies up to the maximum frequency that can
    travel through air on earth atmosphere + 1 KHz. So 1 KHz abve the max
    that can exist in earth's air.
     
  6. BobG

    BobG Guest

    What are you using for a transducer?
     
  7. Phil Allison

    Phil Allison Guest


    ** Change your GG settings - Bob.

    Your post appears with no clue as to whom you are addressing or about what.




    ........ Phil
     
  8. Bob Masta

    Bob Masta Guest

    You don't mention the intended application or the quality needed.
    The Intersil ICL8038 function generator is a one-chip solution (plus a
    few passive parts) that gives sine, triangle, and square and is easily
    tuned over the audio range. Distortion is about 1%, typical of all
    "function generator" oscillators, which shape the sine from a
    triangle.

    Most low-distortion circuits have the drawback that they require
    tracking potentiometers for tuning, though these days digital
    pots with "perfect" tracking make that much easier.

    The simplest way to make low-distortion signals iswith
    your Windows computer and sound card. You can use
    the signal generator in my Daqarta software to make
    sine waves with much lower distortion than most any
    bench-top oscillator you are likely to afford. Plus you
    can make all sorts of other waveforms, and you can
    apply AM, FM, phase modulation or PWM, bursts,
    sweeps, etc... all at once, if you need to! You can
    have 4 of these oscillator "streams" per left/right channel,
    and one stream can modulate others to get dizzying
    complexity.

    Daqarta is nominally shareware, but the signal
    generator is essentially freeware since it continues
    to work after the trial expires. You are welcome to
    use it this way as long as you like.

    Please let me know if there are any questions or
    problems.

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  9. Thank you. I am thinking of a burglar deterrent which would require two
    large speakers, say 300 watt, producing two tones separated by 7 to 10 Hz.
    The two tones could be low, middle or high audio frequency. I suspect that
    two low frequencies would be easiest. Other posters have given me some
    ideas on generating the sine waves but clearly these need to drive some
    large transistors to get the wattage into the speakers. Have you any ideas
    on this?

    Roger
     
  10. Sjouke Burry

    Sjouke Burry Guest

    if I happened to be your neighbor and hat system would
    cut loose in the middle of the night, I would sue you for
    your last penny (or dollar cent/euro cent). :)
     
  11. Here you could not sue. You could complain the council noise control people
    the next day. They would come round in a day or two to listen to the noise
    and perhaps test it with a decibel meter! It is more likely that the
    burglars would go to the police to complain that they were assaulted!

    R
     
  12. Bob Masta

    Bob Masta Guest

    I fear you may be on the wrong track with your basic concept.
    You state that you want a frequency *difference* of 7-10 Hz.
    That won't cause any particular discomfort, just an audible
    beat frequency. Note that beats are an auditory
    phenomenon, not a physical one: The beat frequency (barring
    speaker nonlinearities, etc) only exists inside your head.
    (Yeah, you can "see" the beat rate in the waveform of a
    scope, but it's not there in the spectrum. Check it out with
    Daqarta, if you are curious about this.)

    On the other hand, if you create real sound in the 7-10 Hz
    range, you may be able to excite resonances in the human
    viscera that are alleged to cause extreme discomfort. The
    catch is that it is quite difficult to move enough air to get
    loud sound at frequencies this low. This is well below the
    resonant frequency of most woofers of any reasonable size.

    The early experiments that turn up these visceral resonances
    were with large steam whistles. Later, NASA used large
    electromechanical drivers to shake a person sitting in a chair.
    (Like sitting on a giant woofer!) The were attempting to
    determine human limits for early space flights.

    Best regards,




    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-