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holding the logic

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  • kishore rajendran
    hi, i am doing a project with dtmf decoder. give me some this about it. in this project i should not use any controller or microprocessor. so there is a need
    Message 1 of 5 , Aug 1 3:52 AM
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      hi, i am doing a project with dtmf decoder. give me some this about it. in
      this project i should not use any controller or microprocessor. so there is
      a need that once i press a key and release this pulse form the dtmf decoder
      must be used to turn on or off a particular device.it would be better that
      there will be a button for on and off of device and other buttons for
      selecting which device to be turned on or off. i can connect a decoder to
      out put of dtmf decoder. the problem is that once the key is released the
      logic changes. so i need some thing to hold the same logic once the key is
      pressed and it should hold the logic untill another key press happens, so if
      there is this hold i will use it as a gate signal to triac. send me
      suggestions


      [Non-text portions of this message have been removed]
    • Stefan Trethan
      You asked the same question last week. Please continue one thread and don t just start a new one while ignoring the replies you got. We are not stupid and
      Message 2 of 5 , Aug 1 4:41 AM
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        You asked the same question last week. Please continue one thread and
        don't just start a new one while ignoring the replies you got.
        We are not stupid and asking the same question twice looks like you
        want to waste our time.
        Asking the same question twice won't deliver ready-made schematics
        either if it didn't happen the first time around.

        Now go and read the replies from a week ago, show that you have read
        and investigated the suggestions given and people may be willing to
        assist further.

        ST

        On Sat, Aug 1, 2009 at 12:52 PM, kishore rajendran<rkkr123@...> wrote:
        > hi,   i am doing a project with dtmf decoder. give me some this about it. in
        > this project i should not use any controller or microprocessor. so there is
        > a need that once i press a key and release this pulse form the dtmf decoder
        > must be used to turn on or off a particular device.it would be better that
        > there will be a button for on and off of device and other buttons for
        > selecting which device to be turned on or off. i can connect a decoder to
        > out put of dtmf decoder. the problem is that once the key is released the
        > logic changes. so i need some thing to hold the same logic once the key is
        > pressed and it should hold the logic untill another key press happens, so if
        > there is this hold i will use it as a gate signal to triac. send me
        > suggestions
        >
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >
        > ------------------------------------
        >
        > Please trim excess when replyingYahoo! Groups Links
        >
        >
        >
        >
      • rtstofer
        ... Sounds like school work to me! You can use ring-tailed NOR or NAND gates to form flip-flops: http://wearcam.org/ece385/lectureflipflops/flipflops/ Richard
        Message 3 of 5 , Aug 1 7:00 AM
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          --- In Electronics_101@yahoogroups.com, kishore rajendran <rkkr123@...> wrote:
          >
          > hi, i am doing a project with dtmf decoder. give me some this about it. in
          > this project i should not use any controller or microprocessor. so there is
          > a need that once i press a key and release this pulse form the dtmf decoder
          > must be used to turn on or off a particular device.it would be better that
          > there will be a button for on and off of device and other buttons for
          > selecting which device to be turned on or off. i can connect a decoder to
          > out put of dtmf decoder. the problem is that once the key is released the
          > logic changes. so i need some thing to hold the same logic once the key is
          > pressed and it should hold the logic untill another key press happens, so if
          > there is this hold i will use it as a gate signal to triac. send me
          > suggestions
          >
          >
          > [Non-text portions of this message have been removed]
          >

          Sounds like school work to me!

          You can use ring-tailed NOR or NAND gates to form flip-flops:
          http://wearcam.org/ece385/lectureflipflops/flipflops/

          Richard
        • kishore rajendran
          i have an idea abt the flip flop but this doubt raised . consider d flip flop. first 1 is given as input and now it holds the value 1. now if suddenly there no
          Message 4 of 5 , Aug 6 7:08 AM
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            i have an idea abt the flip flop but this doubt raised . consider d flip
            flop. first 1 is given as input and now it holds the value 1. now if
            suddenly there no input is given that it it neither grounded or given 5
            v(open circuited or high impeadence), will the output of flipflop change.

            On Sat, Aug 1, 2009 at 7:30 PM, rtstofer <rstofer@...> wrote:

            >
            >
            > --- In Electronics_101@yahoogroups.com <Electronics_101%40yahoogroups.com>,
            > kishore rajendran <rkkr123@...> wrote:
            > >
            > > hi, i am doing a project with dtmf decoder. give me some this about it.
            > in
            > > this project i should not use any controller or microprocessor. so there
            > is
            > > a need that once i press a key and release this pulse form the dtmf
            > decoder
            > > must be used to turn on or off a particular device.it would be better
            > that
            > > there will be a button for on and off of device and other buttons for
            > > selecting which device to be turned on or off. i can connect a decoder to
            > > out put of dtmf decoder. the problem is that once the key is released the
            > > logic changes. so i need some thing to hold the same logic once the key
            > is
            > > pressed and it should hold the logic untill another key press happens, so
            > if
            > > there is this hold i will use it as a gate signal to triac. send me
            > > suggestions
            > >
            > >
            > > [Non-text portions of this message have been removed]
            > >
            >
            > Sounds like school work to me!
            >
            > You can use ring-tailed NOR or NAND gates to form flip-flops:
            > http://wearcam.org/ece385/lectureflipflops/flipflops/
            >
            > Richard
            >
            >
            >


            [Non-text portions of this message have been removed]
          • rtstofer
            ... The D flop is clocked. I was thinking about the RS (reset-set) flop. You can use a D flop as RS if it has set and clr inputs. Just ground the D input
            Message 5 of 5 , Aug 6 7:30 AM
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              --- In Electronics_101@yahoogroups.com, kishore rajendran <rkkr123@...> wrote:
              >
              > i have an idea abt the flip flop but this doubt raised . consider d flip
              > flop. first 1 is given as input and now it holds the value 1. now if
              > suddenly there no input is given that it it neither grounded or given 5
              > v(open circuited or high impeadence), will the output of flipflop change.

              The D flop is clocked. I was thinking about the RS (reset-set) flop. You can use a D flop as RS if it has set' and clr' inputs. Just ground the D input and the Clk input (assuming positive edge triggered).

              It is poor practice to let logic inputs float and, in the case of CMOS, can seriously increase current consumption and heating.

              You said you were using a DTMF decoder. Are the outputs active pull-up or open-collector? If they are open-collector then you need to add pull-up resistors. For TTL use something like 1k resistors, for LS-TTL perhaps 4.7k and for CMOS use 10k or so. Or, do the math based on input leakage current, voltage drop across the pull-up resistor and the logic 1 threshold voltage.

              Richard
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