[TI-H] help with hardware


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[TI-H] help with hardware




Hi! My first post to this mailing list. The sketch below shows an early pla=
n for a four-way communication adapter. I don't feel like going through h=
ow it's supposed to work. But I'm looking for potential dangers to the ca=
lculators. As you can see (or maybe not =3D) the calcutors share ground w=
ith the 4.5V battery, could that damage them? Also there are no resistors=
 in this circuit, except the internal resistance in the IC:s. I've heard =
it's quite easy to burn the link-port of the calcs. Anyway, i'm sorry for=
 this messy circuit plan (use fixed width font). Anyway, if there are any=
 (to you) obvious faults to this sketch, i'd be glad if you tell me befor=
e i build it and waste four expensive calculators =3D)

             GND
  __________  |    _____________
  _| " |__  | |___|_            |
  _| 7 |__|_|_|___| |_|_|_|_|_|_|_|
 __| 4 |__|_|_|     |    74153    |
| _| 9 |__|_|_|___  |_____________|
| _| 3 |_ | | |   | | | | | | | | |
| _|___|__| | |   |_|_|_|_|_|_|   |
|___________|_|_____|_|_|_|_|_____|
        |   | |  ___| | | | |
      + |   | | |D|___| | | |
       4.5  | | |A|___|_| | |
      - |   | | |4|___|_|_| |
        |___|_| |1|___|_|_|_|
            | | |4|_  | | | |
            | | |8|_  | | | |
            | | |A|_  | | | |
            | | |_|_  | | | |
           _|_|_______| | | |
          | | |   ______| | |_____
          | |_|__|________|_______|_  
          | | |__|_|______|_|_____|_|_
          | | |  | | |    | | |   | | |
          D D G  D D G    D D G   D D G
          0 1 N  0 1 N    0 1 N   0 1 N
              D      D        D       D

          CALC0  CALC1    CALC2   CALC3


Regards
David Revelj