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Low Volume and FREQOUT — Parallax Forums

Low Volume and FREQOUT

TinkersALotTinkersALot Posts: 535
edited 2010-04-22 02:29 in BASIC Stamp
Has anyone ever had any issue with extremely low volume from a 2PE? I have tried different·'recommended circuits' for driving speakers, including:·capacitor isolation from speaker load; and driving the speaker from an op-amp. Neither of these·provide satisfactory volume levels. Any ideas?

Comments

  • FranklinFranklin Posts: 4,747
    edited 2010-04-20 15:20
    An amplifier?

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    - Stephen
  • ercoerco Posts: 20,257
    edited 2010-04-20 16:03
    A one-transistor amp (2N2222A or equiv) works well with a 330-ohm bias resistor. An LM386 works even better!

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    ·"If you build it, they will come."
  • TinkersALotTinkersALot Posts: 535
    edited 2010-04-20 16:36
    I am driving an LM386 now -- using the "standard gain 200" circuit as found in the data sheet for that device. Output is barely audible -- strange.
  • ercoerco Posts: 20,257
    edited 2010-04-20 17:50
    Something's wrong. You should be able to hear the sound fairly well through a 10 uF-coupled 16 or 32 ohm speaker, and it should be blasting out of a 386.

    Did you toast that pin already? Try another pin.

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    ·"If you build it, they will come."
  • TinkersALotTinkersALot Posts: 535
    edited 2010-04-21 02:14
    That is a good suggestion -- I'll try that. I did probe the current pin with an oscilloscope, and there is signal there when the FREQOUT command is executing. But, I do agree something is wrong for sure. Thank you for that idea, erco.
  • FranklinFranklin Posts: 4,747
    edited 2010-04-21 04:41
    If you used a scope was the value 5v?

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    - Stephen
  • TinkersALotTinkersALot Posts: 535
    edited 2010-04-21 15:54
    Good question, Stephen, I'll verify that today. I expect to take another whirl at this today. -- Yesterday I had the prototype "not in the lab" because I am building this for my daughter and it was at the house for her to enjoy for a bit.
  • TinkersALotTinkersALot Posts: 535
    edited 2010-04-22 00:43
    Progress -- could it be a "current thing?" I tested the swing of the FREQOUT pin with the o-scope and saw 5Vpp (a little less but you get the idea) when the FREQOUT pin was being driven .... I have the stamp, a elab keyswitch device, an elab serial LCD controller and a 4x20 LCD being powered by a single 7805 .... The op-amp was also powered by the regulator, So, this evening I moved the Op-Amp supply to the 9V on the "outside of the regulator" and heard more gain (so much so that as I adjusted the "volume knob" on the input to the OpAmp I started to hear some pretty severe clipping from the speaker.

    So, was I just asking too much of the regulator?

    The more I tinker -- the more I learn...
  • FranklinFranklin Posts: 4,747
    edited 2010-04-22 02:29
    Duh!

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    - Stephen
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