Tone generator

Discussion in 'The Projects Forum' started by frenchie29, Dec 5, 2008.

  1. frenchie29

    Thread Starter Active Member

    Nov 28, 2008
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    Building something similar to a Q box (http://www.whirlwindusa.com/test.html) I have pretty much all the elements but not integrated yet. My next thing is to get a tone generator doesn't matter what frequency, preferably 1k sine wave that I could send out either at mic or line level. Any idea? An IC would be ideal since space is really an issue
     
  2. Wendy

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    Mar 24, 2008
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    The shear number of ways to do this is overwhelming. Me, I'd go with a CMOS 555 as an audio oscillator, then filter it with RC low pass networks till it was clean enough to meet your specs. Quick and dirty.
     
  3. frenchie29

    Thread Starter Active Member

    Nov 28, 2008
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    That's what I had in mind a 555

    Now how do I make it work as an oscillator????
     
    Last edited: Dec 6, 2008
  4. Wendy

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    Mar 24, 2008
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    http://forum.allaboutcircuits.com/showthread.php?t=15342

    If you read the article you'll see why I recommend a CMOS chippie.

    Followed by:

    [​IMG]

    This will convert it to a pretty good approximation of a sine wave. You might even want to add a few more stages, the more RC filters it goes through the cleaner the waveform will be.
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. SgtWookie

    Expert

    Jul 17, 2007
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    See the attached for a fairly simple LC tank sinewave oscillator.

    If the inductor had a moveable ferrite core, the frequency would be adjustable.

    [eta]
    Changing R2 to 510 Ohms, C1 to 39uF and L1 to 640uH would give you right about 1kHz at 17v P-P. You could use a 10k pot as a level out control with one end connected at point (C), the other connected to ground with the wiper for signal out.

    Better yet, use the other half of the LF353 or TL082 as a voltage follower, as in the 2nd attachment.

    Making a 640uH inductor:
    1) Take a Bic pen barrel (one of the cheapies) and glue on two cardboard disks/washers with exactly 1/2" space between them (no glue between the disks.
    2) Wrap 327 turns of AWG 30 magnet wire on the barrel in between the disks, making each of the seven layers as neat and tightly together as possible. This will take about 36 feet of wire. The resulting coil will be just under 1/2" in diameter and slightly over 1/2" long.

    C1: must be non-polarized. A single polarized aluminum electrolytic caps will not work, however you could use two 82uF caps back-to-back to create a non-polarized 41uF cap. Poly caps will give a much cleaner sinewave.
     
    Last edited: Dec 6, 2008
  7. Wendy

    Moderator

    Mar 24, 2008
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    Those circuits work, but gain is always an issue for a clean sine wave. The OP needs very small signals too, audio input and mic level.
     
  8. ssherwood

    New Member

    Aug 25, 2008
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    I am also trying to build a tone generator, and have been changing caps and resist. in the circuit to change Hz.
    But when I get near my target of 1400 Hz the output distorts and jumps around on the oscilloscope. The closest I get with a good signal is 1370 or so by changing the 10k to about 2k. If I move my POT even more, it distorts, then will clear up again at around 1530 Hz (sort of clear). Any ideas?

    Sorry, I am new at this, and the mathematics didn't work out for me...if anyone could help with my issue and/or a formula for finding a specific Hz. it would be greatly appreciated. Thanks so much to you Gurus who take your time to help us guys out. Circuit is at http://hop.concord.org/s1/core/s1ca1.html#top
     
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