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Analog to Digital Converter

Discussion in 'Electronic Basics' started by [email protected], Mar 29, 2007.

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  1. Guest

    Hi guys i am in the process of trying to figure out how and where to
    start to build a Analog to digital converter for a project. I have
    done some research and it seems that at the basic level its nothing
    more that a pulse oscillator circuit followed by a comparator. The
    specification i must stick with are :
    1. max input freqeuncy 100khz
    2. successive approx type with best guess centering
    3. max bits are eight
    4. max error of 1% at output

    If anyone can direct me to some circuit diagrams or information, i
    would appreicate it.

    thanks
    peter
     
  2. Dan Coby

    Dan Coby Guest

    This looks like another example of someone asking for help with their
    homework assignment.
     
  3. Chris

    Chris Guest

    Hi, Peter. Actually, you're supposed to put a dab of quicksilver in
    the loaf before you set it afloat. It stops in the newsgroup right
    over the answer to the homework question. All ah see heer is a plain
    loaf. ;-)

    Not that you really need this, but you might want to look at Analog
    Devices Appnote AN-289. No link -- as a bonus, you'll have to look it
    up yourself.

    If it "seems that at the basic level its nothing more that a pulse
    oscillator circuit followed by a comparator", you've got a bit of a
    haul.

    Good luck
    Chris
     
  4. Bob Masta

    Bob Masta Guest

    Successive approximation types are built around a D/A
    converter and comparator. You compare the input signal
    to the output of the D/A. Toggle the MSB of the D/A and
    if the D/A output is now too big (comparator switches) you
    turn that bit back off. Continue for all bits.

    You can build a dead-simple D/A for this from a simple
    R-2R resistor ladder, driven by any decent CMOS
    digital output. A buffered printer port on an old PC
    works fine. Full discussion of this, and software to
    run it, at
    www.daqarta.com/lptx.htm

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  5. Rich Grise

    Rich Grise Guest

    Well, you have to give him a point for disguising it well^H^H^H^Hbetter
    than most. ;-)

    Cheers!
    Rich
     
  6. Rich Grise

    Rich Grise Guest

    64X LM339 + 8X 74HC148 + a buffer & some glue logic should do it. ;-)

    Or maybe that should be 9X 74HC148 ;-)

    Oh, wait! That's a flash converter - the teacher wants an(a) SAR. >:->

    Cheers!
    Rich
     
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