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Very Very Low Frequency Generator

Discussion in 'Electronic Components' started by [email protected], Dec 25, 2006.

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  1. Guest

    Hi all,
    I'm looking after a sine (or triangle) wave generator, but with really
    low frequency.
    I read about a compennt called ICL8038 which looks really great but had
    a frequency of only 0.001Hz - That's not enough for me!

    I need the whole cycle to take more then 30min = frequency of about
    0.0005 Hz.

    I'll be glad for any help, information, advice, etc..
    Thnks, me.
     
  2. Jamie

    Jamie Guest

    Learn to program a PIC or AVR. They have simply varieties that
    can handle what you need.
    You need to use a PWM output and some simply code to calculate
    the steps needed on the output.
     
  3. Use a motor driven pot.
     
  4. Salmon Egg

    Salmon Egg Guest

    Why not just do it with your computer. Compute sin (0.001*¼*t) using your
    system clock? Send the output to an D/A converter with a filtering
    capacitor, and voila.
    -- Fermez le Bush
     
  5. Guest

    First thanks.
    I see that there is no way to avoid PIC programing (which is new to
    me).
    But what can you do.. a bit smoke here and there, maybe a burned
    circuit or four.. I'll be alright.
     
  6. Of course there are plenty of other ways. You just have to learn
    electronics to get it right.

    There is nothing magic about a sinewave where you want, it's just
    a matter of scaling things down. But, you will end up with really
    large value components. I doubt there is anything intrinsically
    wrong with the 8038 at low frequencies, but once you use large
    enough value components to get those low frequencies, the 8038 will
    start loading down the components and mess things up.

    Take a 1KHz oscillator using an coil and capacitor and scale those
    values down, and it will work. But you'll end up with really large
    values.

    Take a higher frequency clock, run it through a divider, and then
    use some method to convert it to a sinewave. A simple low pass
    filter might work, though again you end up with large value
    capacitors. A stepped sine wave might be suitable, depending on your
    specific use. So you can do the conversion with some resistors and
    a ripple counter, or a ROM lookup table and an D/A converter.

    But, since you had to ask a general how to do it, then of
    course someone's going to suggest a computer to do it, and you have
    nothing to put that answer in context.

    Michael
     
  7. As (almost) always there are more ways to skin a cat. But scaling down alone
    will have a serious drawback: time. It may take seconds for a 1Hz sinewave
    oscillator to stabilize. A 0.001Hz sine wave oscillator may need hours, a
    0.0005Hz one may need days. You can of course refine the design to handle
    the problem. Nevertheless, I doubt someone will build an oscillator like
    this using only analog technics these days. But it sure can be done.

    petrus bitbyter
     
  8. ISTR that Don Lancaster has discussed related matters on tinaja.com
     
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