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Sine Tone Generation Help!

Discussion in 'General Electronics Discussion' started by FailSafeIndigo, Aug 24, 2012.

  1. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    Hello! I randomly stumbled on this site looking for answers, and you guys seem pretty smart ^_^.

    I'm wondering, is there a cheap an effective way to generate sine tones (or close to) using small electronic components?

    I had a look at using 555 ICs, but it seems they generate square waves =/. I don't need to have perfect sine waves, but I need a rather pure sound! I know that turning those square waves closer to sine waves is possible, but at that point the circuit starts getting bulky, and unfortunately size/space is an issue.

    Specifically, I need several stand alone circuits that each produce a different pitch. I intend to use a 19-tone equally spaced music scale, so being free to specify any pitch between 100hz and 500hz is very important, but they don't need to be adjustable. The pitch each circuit produces doesn't need to change, so ideally each circuit need only be [Component(s) generating specified pitch + battery + speaker].

    I've had a look around, and I've found some things that might be suitable, but are very expensive! I am but a poor student, with dreams of creating annoying noises =(. My electronics skills are limited, but just a point in the right direction for component(s) that would be most suitable would be more than enough to get me started!

    Any help would be greatly appreciated! Thank you =D.
     
  2. BobK

    BobK

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    Jan 5, 2010
    Are you saying that you want to build 19 circuits each producing a different frequency sine wave? There are probably better ways to go about this, depending on your needs. If you are using this for music synthesis, you almost certainly do not want sine waves. Tell us more about what you are trying to accomplish.

    Bob
     
  3. CocaCola

    CocaCola

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    Apr 7, 2012
    We live in the digital age, except for a few anal analog audiophiles the rest of the human population is quite happy with the sound produced from square waves... Is it 'pure' no, but for the human ear that has it's limitations it's quite acceptable for audio reproduction in almost all cases...
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    Hi there, welcome to the forums :)
    And if you, as you say, are a poor student, then the last thing you need is to build 19 identical circuits, that just a of extra work and components. Thats gonna get expensive

    a question ... do any of the tones need to be produced at the same time ?....or a single different freq tone at any given time ?

    As BobK said.... what are you trying to achieve ?

    Dave
     
  5. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    Electrobrains: looks like I'll have to investigate op amps a bit further =). Thanks for your help!

    BobK: I'm afraid I certainly do want sine waves! And in fact, I need to produce 83 of these circuits, to be spread around a room. They need to be rather small and portable; the speaker I am using is about the same size as an earphone (but considerably louder!) A signal generator, as has been proposed to me numerous times, is just not a viable option =/. As for more about what I'm doing, that's it really! Sounds like nonsense, definitely, but to elaborate further would deviate from the subject into the world of abstraction lol. You mentioned better ways of creating this - I'd really like to hear them =). Thanks for your reply!

    CocaCola: I must admit to being guilty of the crime of audiophillia haha =P. Perhaps you are right though - I may have to concede defeat to the square wave! Thanks for your reply! =).
     
  6. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    Davenn: Thanks for the welcome =D. Unfortunately, I need 83 of these circuits, and they are all playing simultaneously D=. When I say that I'm a poor student, I mean hat I can't afford to spend more than £2 per circuit on the component(s) I need. Capacitors, resistors, wires, batteries and such are negligible =). Thanks for your reply!
     
  7. CocaCola

    CocaCola

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    Apr 7, 2012
    I have never seen any verifiable proof that even the most anal audiophile could accurately identify a digital from analog audio track in a controlled scientific setting with unaided ears... Especially if the digital track contains or 'spoofs' the analog noise and artifacts from the analog medium used...
     
    Last edited: Aug 24, 2012
  8. Sage

    Sage

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    Aug 24, 2012
    Research the Wien bridge oscillator...
     
  9. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    CocaCola: I'm afraid you've lost me there with the analogue and digital comparisons. I certainly don't think I'm unique when I say that I can tell the difference between a sine wave and a square wave. The production of either sine or square waves would have to be digitally produced, in any case, as they are not exactly commonly occurring! ^_^. Thanks for your insight =).

    Sage: thank you! I will look them up now =)
     
  10. CocaCola

    CocaCola

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    Apr 7, 2012
    In a pure unaltered wave form yes, but not if the goal of the created square waves is to imitate the sine wave of an audio frequency for the human ear...
     

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  11. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    I can't say I've ever encountered that haha. I should mention that I am rather unique in,that I have perfect pitch to a 36 tone scale (most perfect pitch possessors follow the twelve tone scale of western music); I have a rather good ear for sound! I concede defeat to you - what I hear and what others hear are probably quite different! I would very much have liked to have used sine waves though =(. It's all well and good if the general public can hear it the way I meant it, but its a little disappointing that I won't! I thank you for all your help =).

    Ah, I just saw the attached image! I understand what you mean, but I think to try and build an electronic circuit capable of doing that would get a little complex; I've gotta build 83 of these! =P. Thank you for your help =D.
     
    Last edited: Aug 25, 2012
  12. CocaCola

    CocaCola

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    Apr 7, 2012
    I'm 100% sure in a blind controlled test you would not be able to hear the difference... CD audio was on the verge of leveling that playing field between analog and digital audio, but now with higher sample rates, forget about it digital has far surpassed what the human ear can distinguish, even an exceptional ear like yours...
     
  13. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    I do apologise, I missed the attachment, and misunderstood what we were discussing! You are correct, of course, but I cannot see the connection between your points and my circuitry needs. I need 83 of these circuits, each of them as a stand-alone unit. Otherwise, I'd simply write a piece of software to do the job!
     
  14. CocaCola

    CocaCola

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    Apr 7, 2012
    Well it is the year 2012 and you could do both ;) Using PWM from a micro with a built in 'Sine Simulation' look up table, or mathematical calculations, you get a digital representation of a sine wave using square waves... See how it applies now?

    A proof of this concept can be seen here, complete with the look up tables ;) although they use an external DAC vs PWM...

    http://www.myplace.nu/avr/minidds/index.htm
     
    Last edited: Aug 25, 2012
  15. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    I see indeed! I'm afraid 83 micros might be a little out of my budget though =P. I shall investigate further =). Thanks for all your assistance ^_^.
     
  16. CocaCola

    CocaCola

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    Personally I believe your budget is borderline unrealistic for a stable trouble free design from the ground up, certainly unrealistic for a solid design on manufactured PC boards... But, you might be surprised at how affordable this can be done with micros...
     
    Last edited: Aug 25, 2012
  17. FailSafeIndigo

    FailSafeIndigo

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    Aug 24, 2012
    Hmm... I'll have to do some research into this... Maybe my project is a bit much=/. I'm the only girl in my lectures, so I kinda feel like I need to prove myself hahaha. Well, I thank you very much for your help! I'll be sure to post my progress =D.
     
  18. Sage

    Sage

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    Aug 24, 2012
    You didn't mention the required power to the load. A 555 can output enough to drive an EM speaker, but most op-amps and micros can't. Most can drive a small piezo speaker at low volume; if you go with a low-power front end you may need a separate amplifier if you want more output than that.

    For a stable, low distortion, audio frequency sine wave you won't get much simpler than the Wien bridge oscillator (it also has a simple compensation mechanism and it's inexpensive). And, a Wien bridge can be built with a low-cost integrated amplifier like an LM386, possibly eliminating the output amplifier stage (depending on your requirements).

    You can also use practically any LC oscillator variant if you can tolerate the larger inductor/capacitor values you'll need for your frequency range; cost might become an issue here (and there are some other subtleties that need to be addressed).

    By the way, if you're willing to use a separate amplifier stage than you have other options, but cost and size increase. From your initial description it didn't sound like you were interested in a separate amp or digital synthesis, but rather just wanted to create some pure audio tones, simply. As CocaCola noted, you can use a micro to synthesize an analog sine wave with a fidelity that's probably beyond the range of even Superman's discerning powers (well maybe not Superman, but you get the idea). And micros can also be cost effective if you know what you're you're doing with them (but you'll probably need an amp unless you're satisfied with the piezo volume).
     
  19. CocaCola

    CocaCola

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    Apr 7, 2012
    They can still be cost effective, an LM386 circuit adds about $1.50, the micro is about $1.50, a few more pennies for misc components and you are right in the budget area less the speaker of course... Not saying it's the cheapest solution but IMO it's one of the more adaptable and stable ones in the end...
     
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