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Audio Input

LowIQGeniusLowIQGenius Posts: 13
edited 2009-02-26 19:24 in Propeller 1
Does anyone out there know of a good way to interface an audio jack as an input with minimal hardware?· I'm hoping to use the signal from the jack to drive a small NPN·transistor and can't check my theory right now.· Any ideas?

Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2009-02-26 06:35
    Just use the A/D network with the two capacitors and the feedback resistor (like on the demo board) but AC couple the input through a suitable value resistor (try 100K) to suit the input level.

    *Peter*
  • virtuPICvirtuPIC Posts: 193
    edited 2009-02-26 09:37
    For A/D driver have a look at the object exchange: obex.parallax.com/objects/58/. I tried it. It works fine!

    And have a look at the schematics of the demo board. It has a microphone connected to the prop via just a few resistors and capacitors. To connect to an audio jack I would decouple with a capacitor.

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  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2009-02-26 10:38
    Forgive my simple explanation but the A/D circuit works by balancing the charge on the capacitor network so it won't work if you drive the input via low impedance as the feedback resistor can't compensate. The microphone circuit is inherently "high impedance" enough that it just works nicely. If you add a resistor in the input circuit (along with the capacitor of course) the worst that can happen is that you might change the value but whatever you do, add a resistor.

    *Peter*
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2009-02-26 15:11
    Here is a Ganster Gadget project which handles audio input with minimal hardware.

    OBC

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    New to the Propeller?

    Check out: Protoboard Introduction , Propeller Cookbook 1.4 & Software Index
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  • virtuPICvirtuPIC Posts: 193
    edited 2009-02-26 15:35
    Oldbitcollector said...
    Here is a Ganster Gadget project which handles audio input with minimal hardware.

    Looks great! However, schematic would have been nice. Will reverse engineer it tomorrow...

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Airspace V - international hangar flying!
    www.airspace-v.com/ggadgets for tools & toys
  • LowIQGeniusLowIQGenius Posts: 13
    edited 2009-02-26 18:21
    Thanks for the help! I'm gonna try to get a schematic done for the gangster kit (hope it's legal).
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2009-02-26 19:24
    I doubt that Nick will mind us poking around with his project, but if you post it somewhere I'd
    post a direct link to the project on Gadget Gangster. I'm sure he will appreciate that.

    @Nick, am I wrong here? [noparse]:)[/noparse]

    OBC

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    New to the Propeller?

    Check out: Protoboard Introduction , Propeller Cookbook 1.4 & Software Index
    Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
    Got an SD card connected? - PropDOS
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