Laying out IC's on a board

Discussion in 'The Projects Forum' started by jgessling, Jun 6, 2010.

  1. jgessling

    Thread Starter Active Member

    Jul 31, 2009
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    14
    A while ago I finished my breadboard version of my 4 digit LED clock. Built with 7400 TTL and 7 segment displays, the schematic is in the projects collection. I'm trying to build it now on protoboard, like 1 hole island. The 7 segments must be vertical of course but I can't decide whether to make the rest of the chips in horizontal or vertical rows. I started vertical but then the wires from the 7447 segment drivers are all on top of each other as they run from a vertical row of holes at the 7447 to the displays.

    If I make the 7447 chips in a horizontal row, then the wires would have to jump over the chip to get up to the display above. (or I could put some wires on the bottom of the board). I hope this makes some sense, my conundrum that is.

    On a related note, why are chips laid out the way they are, I mean the pins? Like the 7447 for example has all the segment pins on one side but they are not in a convenient a-g order, they go like f,g,a-e. Or like the 7490, why are the binary outputs not simply a,b,c,d instead of a,d,b,c? Was this for the convenience of the chip maker or is this supposed to help me in some way when hooking the chip up to the display.

    Any thoughts appreciated, even if the answer is to stop stressing over this and get to building.
     
  2. luzagodom

    New Member

    Jun 3, 2010
    1
    0
    If I make the 7447 chips in a horizontal row, then the wires would have to jump over the chip to get up to the display above. (or I could put some wires on the bottom of the board). I hope this makes some sense, my conundrum that is.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    My favorite is still wire-wrap for one-off. Sockets cost more then the IC's.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I suspect chip designers have the same problems as board designers X1000. Unlike board designers if they can get the logic out it doesn't matter which pin, other than the power supply pins, which are highly standardized.
     
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