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Help with this circuit, please ( drawdio )

  1. Sep 10, 2009 #1
    Help with this circuit, please... ("drawdio")

    I was trying to build this circuit... http://www.ladyada.net/make/drawdio/design.html
    however, I am unfamaliar with the amplifiers, as well as how different types of capacitors effect frequency. What 'kind' of amplifier should I be getting, and must I use a tantulum capacitor (and is there any way to ensure that this tantulum was not used to fund horrible exploitation of labour or civil war)? Also, if someone could be so kind as to give me links to generalised information, I suppose I could check wikipedia but that is sometimes hard to understand - that would be appreciated as well.

    Thanks!
     
  2. jcsd
  3. Sep 10, 2009 #2

    berkeman

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    Re: Help with this circuit, please... ("drawdio")

    C4 and C2 are the only caps that need to be polar. Electrolytic caps should be fine. I didn't see mention of a tantalum cap, but could have missedit.

    Also, C2's use is a bit of an error. You can't use a polar cap in a non-polar application like the C2 position. That should be two polar caps placed back-to-back, to form a non-polar cap of half the value.

    And the output push-pull stage is kind of dorky, especially running off just a 1.5V power supply (less as the battery discharges). It's going to put out a very distorted signal...
     
  4. Sep 10, 2009 #3

    berkeman

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    Re: Help with this circuit, please... ("drawdio")

    And on your question of learning resources... I recommend that you check out the book "The Art of Electronics" by Horowitz and Hill. You will get a lot of value of out it. Check out a copy at your local technical library, or buy a copy from Amazon.com
     
  5. Sep 10, 2009 #4

    vk6kro

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    Re: Help with this circuit, please... ("drawdio")

    You won't need any amplifier with this circuit as it is already intended to drive a speaker.

    The output of a 555 is already a square wave, so extra distortion won't matter.

    C2 can be a polarized capacitor because it has a DC voltage on it.

    You can choose normal electrolytic or Tantalum. Tantalums are smaller and have lower leakage.
    I don't know about the politics, but there is no way of knowing where the Tantalum comes from.
     
  6. Sep 11, 2009 #5

    berkeman

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    Re: Help with this circuit, please... ("drawdio")

    Ah, good point. The diagrams in the link suggested analog sine waves, but you're probably right since it's meant to be a 555-like IC.

    Interesting. I think you are right about this as well, but I need to think about it WRT the reactive impedance of the speaker coil. But for an initial pull-down from quiescent center bias waveform, I'm still not sure. Seems like you could maybe get a bit of neg bias, but probably not or not much. Thanks vk6kro.
     
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