Analog Keyboard Circuit

Discussion in 'General Electronics Chat' started by rac1, Jan 27, 2013.

  1. rac1

    Thread Starter New Member

    Apr 8, 2012
    5
    0
    Hi
    I searched for keyboard circuits but didnt find anything which i want to do.

    I want to do a circuit that only sends to the computer "a" button.(It can be any other buttons)
    How can i do that?
    I dont have any idea about it. I think , if i bought a new keyboard and if i open that keyboard,I can see what there is inside it, but I dont want to kill a keyboard.
    Help please.

    Any idea or any circuit will make me happy.

    Thanks
    Rac
     
  2. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    Most keyboards send serial data to the computer. What kind of computer, how many keys, etc. do you want. There is a way to use various voltage levels to represent various keys, if that is what you are looking for, but the more keys, the more complicated.
     
  3. BReeves

    Member

    Nov 24, 2012
    412
    64
    The Teensy 2.0 for $16.00 will do exactly what you want.

    http://www.pjrc.com/teensy/

    You can download a keyboard program from the web site that can be loaded into the Teensy with the Adrino software also available on the site. It will plug into a USB port and you can set up switches on the input to simulate any key on a keyboard. It's all explained on the web site if you look around a bit.

    I'm am not affiliated with PJRC other than using the Teensy for a couple business projects.
     
  4. gootee

    Senior Member

    Apr 24, 2007
    447
    50
    You wouldn't need to open the keyboard itself just to see what goes through its connector when a key is pressed. You would only need to access the connections to the computer, maybe with a special adapter you could make that has external connections, and then use some other port or computer or test equipment to observe the signals. But it would probably be easier to look it up, on line, somewhere, perhaps in the source code for a keyboard driver.
     
  5. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
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    We can keep guessing as to what the OP really needs and until he answers some basic questions I don't think he will get much meaningful help. Title of the thread is ANALOG KEYBOARD CIRCUIT so until that is clarified along with what exactly does "a" mean we are all in the dark.
     
  6. gootee

    Senior Member

    Apr 24, 2007
    447
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    My guess is that he wants a circuit that, when connected in place of a keyboard and activated, does the same thing a keybaord would do if the "a" key were pressed.
     
  7. BillB3857

    Senior Member

    Feb 28, 2009
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    So where does the Analog come in?
     
  8. gootee

    Senior Member

    Apr 24, 2007
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    Maybe he wants to make all of the gates and flip-flops from discrete transistors. <grin>
     
  9. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    The basic idea of all keyboards is the SPST switch. It is either open or closed. If a collection of switches is arranged in a two dimensional array of `m' rows by `n' columns you can decode "switch closures" by enabling a row and checking for closed switches. If there are "closed switches", then you hold in that state until all the switch(s) are released. If not you move onto the next row. When you finish with the last row you move back around to the first row.

    Wash, rinse, repeat.
     
  10. BillB3857

    Senior Member

    Feb 28, 2009
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    That sounds digital to me. OP wants ANALOG.
     
  11. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Everybody is free to attempt an analog implementation, and I'm not sure I have any good ideas. He was talking about taking one apart and at least he doesn't have to do that anymore.
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
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    Here is one way to do it.....
     
  13. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Why not waiting say, 24 hours, for him to explain what is the analog part of it? Guessing after guessing is futile here.
     
  14. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348

    May be, but it keeps the creative juices flowing:D
     
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