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567 Tone Decoder - Anyone ever try this? — Parallax Forums

567 Tone Decoder - Anyone ever try this?

Beau SchwabeBeau Schwabe Posts: 6,568
edited 2010-05-11 17:00 in General Discussion
Just thinking out loud...

Has anyone ever tried omitting the timing resistor and capacitor off of pins 5 and 6, and directly driving pin 6 via a current limiting resistor at the desired frequency that you want to decode on pin 3?

... might work for a 'programmable' frequency decoder.

Anyway, just a thought.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Comments

  • Dr_AculaDr_Acula Posts: 5,484
    edited 2010-05-11 09:09
    That could work. There probably is a 4046 solution as well. Mind you, would the 'modern' way be to synthesize a 567 in a cog on a propeller?

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    www.smarthome.viviti.com/propeller
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2010-05-11 15:45
    Dr_Acula,

    "Mind you, would the 'modern' way be to synthesize a 567 in a cog on a propeller?" - it might.

    I think though that the 567 might have a better advantage over the Propeller of detecting a tone within multiple tones. Sleeping on it and looking over the schematic of the 567, I believe that the 567 uses the pseudo triangle wave generated from the RC timing to derive a quadrature signal from the zero crossing points. By comparing the quadrature signal to an unknown input it can then determine the presence or non presence of a tone in a way similar (the analog equivalent) to the Audio spectrum analyzer I posted some time ago.

    Saying that and applying my original question of anyone ever trying something like this, I think you would still need the RC components, however the connection to/from pin 5 would be omitted and your signal (from the Propeller) would enter through the resistor there. As long as you are applying a 'square wave' the RC would act as an integrator, creating the 'expected' pseudo triangle wave at pin 6.

    The reason for using the 567 in the first place would be to take some of the analog complexity out of the equation.

    Again, just thinking out loud and wondering if something like this would be possible.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2010-05-11 17:00
    I thought about replacing the 567 in software but found them at such a price
    that it was not worth the time and trouble.

    38 cents each, delivered from Taiwan.

    cgi.ebay.com/50pcs-LM567-DIP-/370375706449?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item563c1cc751
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