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logic design question

Discussion in 'Electronic Basics' started by panfilero, Oct 19, 2006.

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  1. panfilero

    panfilero Guest

    Hello, I'm trying to build a circuit that has an array of switches (8
    switches) and takes in a clock signal and compares the clock signal to
    my switches one at a time. Then if both the clock signal and the
    switch are "high" i would like an input signal to be connected to my
    output. Anything else should result in a break between my input and
    output signals. I'm having a hard time getting started with this
    project and was wondering if anyone had any suggestions on how I may
    accomplish this. My input is a very small audio signal.

    thank you.
  2. Hmm... Your description is not very clear, at least not to me. So you have
    an input signal (one?), small audio, that should be connected to an output
    (one?) or not depending on some clock. How does this clock arrive? At what
    time do I compare what part of that clock to what switch? What's next? It
    may be usefull to tell more about the background too.

    petrus bitbyter
  3. PeteS

    PeteS Guest

    While contemplating your response to Petrus, you may also contemplate
    cross posting rather than multiposting :)

    Crossposting ensures that a reply goes to all the newsgroups you posted
    to, so anyone interested sees the reply regardless of where it came from.


  4. panfilero

    panfilero Guest

    ok, the signal is from a guitar, the output is to an amplifier. i
    believe the audio signal from the guitar to be pretty small...
    millivolts i assume. the clock i'm thinking i will make from a 555
    chip, i would like to be able to control the speed of the frequency. i
    have 8 buttons, when i push a button that button should be "high", my
    goal is to make something where a clock signal is constantly being
    compared to these 8 buttons. Whenever my clock signal is a "high" and
    the button is a "high" i would like the input to be connected to the
    output, else i would like it to be off. So, if I press all 8 buttons
    then my output would be an audio signal that is only on when my clock
    is "high" and it should sound like a stutter. If 1 = connected (sound)
    and 0 = not connected (no sound) then when all 8 buttons are pressed i
    should hear 1,1,1,1,1,1,1,1 this should be continuously looping. If
    the 3rd,4th,6th,7th,8th button are pressed I should hear
    0,0,1,1,0,1,1,1 coninuously looping. If i increase my clock speed,
    then my logic circuit would just loop through these 8 buttons quicker.
    I'm guessing I'm comparing the clock with each button using an AND
    function. Audio should only come out if both clock AND button are

    thank you, i appreciate any suggestions of how to get started with this
  5. panfilero

    panfilero Guest

    this is actually my first time posting in these things.... how do i
    cross post? thank you
  6. Like Newsgroups: sci.electronics.basics,
  7. Randy Day

    Randy Day Guest

    panfilero wrote:

    Is this the kind of thing you want?

    This is *not* an engineered circuit, and may
    not work in practice, but maybe it will give
    someone ideas...

    Set up an 8-bit shift register in a ring
    configuration, with switches off the outputs
    as shown. Pre-load the register with a 1,
    then cycle it with the clock. Each time the 1
    hits a closed switch, the transistor base goes
    high, turning on a relay, pre-amp or audio

    | | |
    .-. | 555 |
    | |<--| |
    | | |timer |
    '-' | |
    | '---.--'
    | T
    .--V----. ---
    | |---o o------------.
    | | T |
    | | --- |
    | |---------o o------| VCC
    | | T | +
    | | --- | |
    | |---o o------------| .------.
    | | T | | |
    | 8-bit | --- | | pre |
    | |---------o o------| in -| amp |- out
    | shift | T | | |
    | | --- | | |
    | reg. |---o o------------| '------'
    | | T | |
    | | --- | ___ |/
    | |----------o o-----+-|___|--|
    | | T | R |>
    | | --- | |
    | |---o o------------| |
    | | T | ===
    | | --- | GND
    | |----------o o-----'
    (created by AACircuit v1.28 beta 10/06/04
  8. Well,

    Suppose you know how to build that 555 clock. Keep in mind that when you
    change the frequency, you may change the pulse-pause rate (duty cycle) as

    Then you need a 3 bits binary counter. The precise type does not matter as
    long as it counts binary. A 74HCT163 or CD40163 will do. (They're 4 bits
    counters, you only use the three least significant bits.) The counter just
    has to count from 000bin up to 111bin and start all over again.

    Next you need an eight input multiplexer. 74HCT151 for instance. Connect the
    counter outputs to the select inputs and the buttons to the multiplexer
    inputs. Now the multiplexer output will show the button values one by one.
    An AND-gate and you're done with the logic.

    As for the switch consider a CD4066B. You may set all four switches in
    parallel to reduce the internal switch resistance. An AND-gate can easily
    drive them all.

    petrus bitbyter
  9. Lord Garth

    Lord Garth Guest

    Additionally, you cannot allow the audio signal to go negative, with respect
    to ground,
    if the 4066 is running on a single ended power supply such as 5 volts and

    Doing so will destroy the 4066. The solution is to run a bipolar power
    source such
    as +5 volts, -5 volts and common ground.
  10. panfilero

    panfilero Guest

    Appreciate the suggestions, I think they will definitely help me get
    started on this thing. Thanks!
  11. panfilero

    panfilero Guest

    that sounds about right, the part that gets me is how to make it
    sequence, and check each and gate one by one and then loop and check
    them again.

  12. Lord Garth

    Lord Garth Guest

    A previous poster suggested you use a counter / decoder to sequence
    your clock through the 8 switches, one at a time.

    This is still a correct answer!
  13. Jamie

    Jamie Guest

    Use of AND gates seems to fit your delima!
    The AND gates for the sampling would simply use the clock
    and what ever input your sampling. if both are high for example,
    the AND gate output goes high, that in turn can turn on another
    INPUT of and gate, where is, the other input of this gate
    will have your passive signal you want to gate through .
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