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EMIC eliminate background noise — Parallax Forums

EMIC eliminate background noise

shmowshmow Posts: 109
edited 2008-07-20 12:24 in BASIC Stamp
Hello all,

I have the EMIC module output terminals connected to my stereo (EMIC and Stamp2 are on a BOE).
There is some humming in the background.· I checked the forum and the only thing I understood - being a novice at this - was to connect a capacitor on the EMIC's output.

Is there anything else I can do to eliminate or reduce the background noise?

Regards,
Shmow

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2008-07-14 19:22
    Usually this is a symptom of poor grounding. Do you have the 'shield' wire connected to Vss?
  • shmowshmow Posts: 109
    edited 2008-07-14 19:28
    What is a shield wire?
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-07-14 19:29
    Well, the audio wire going out to your stereo should have a 'ground' wire on it. If you used co-axial wire, the 'ground' would be the 'outside' wire, while the 'signal' would be the 'inside' wire.
  • shmowshmow Posts: 109
    edited 2008-07-14 19:37
    I am using audio cable (just two wires and no ground wire).·
    It doesn't look like the BOE has a ground terminal.
    ·
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-07-15 14:21
    True, it doesn't. What have you tied those two wires to on the BOE side?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-07-15 15:29
    The BOE ground is VSS. More importantly, which output from the Emic are you using to go to a stereo system? You should be using the analog out rather than the speaker output. In this case the speaker output may not be a problem, however the speaker outputs on some circuits have a differential system and are not common ground.

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    Chris Savage
    Parallax Tech Support
  • shmowshmow Posts: 109
    edited 2008-07-15 18:48
    Guys,

    I never thought to use the analog out.
    If I was to use that connection with the audio cable then
    I would connect the + terminal (red) on my stereo to the analog output on the EMIC and
    the - terminal (black) on the stereo·to the gnd on the EMIc. Is this correct?

    Regards,
    Shmow
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-07-15 19:09
    Hmm. "Red" and "Black" on a stereo (and "+" and "-" connections) could be "Speaker Output" terminals -- you probably shouldn't connect the EMIC card to those.

    Now, if you had RCA inputs (little concentric circle connectors) then the inner pin should connect to the EMIC analog, and the outer ring should connect to the EMIC ground.
  • shmowshmow Posts: 109
    edited 2008-07-16 01:15
    I do have the RCA connectors!
    I will wire those in tonight.
    Thanks for your help.
    Regards,
    Shmow
  • shmowshmow Posts: 109
    edited 2008-07-16 17:07
    I connected the one end of the RCA audio cable to the stereo, and at the EMIC I connected

    the other end of this cable -·positive to the analog out and the negative to the GND.

    There is still a humming noise.

    I connected a capacitor in series with the analog output of the

    EMIC, trying different values·(22·to 100 microF).

    I don't think the clarity won't get any better.· I'm trying to get it so people in

    a small warehouse can hear her voice.

    Regards,

    Shmow
  • denodeno Posts: 242
    edited 2008-07-20 12:24
    What sort of power are you running your BOE with?· Is it from a 'wall wart' (aka transformer-rectifier plugged into the wall) or from a battery?· If it is the 'wall wart" try a battery, and see if the HUM goes away.· It could be bad filtering in the 'wall wart'.

    Deno

    PS...I have this problem (but live with it) on my talking sprinkler system where I am using a 'wall wart' for power.
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