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Re: Micro/Elf expansion schematics

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  • sbirdasn
    True, there are issues/hassles with the TTS method of PCB s. It s a classic case of Your Mileage May Vary in action. I have an HP LJ 1100, and it is fairly
    Message 1 of 8 , May 21, 2004
      True, there are issues/hassles with the TTS method of PCB's. It's a
      classic case of "Your Mileage May Vary" in action.

      I have an HP LJ 1100, and it is fairly accurate in the width
      dimension, while the length (feed) dimension is definitely off and
      differs from media to media. Moral of the story: Do critical additive
      dimensions in the non-feed axis. Scaling can address some printer
      driver issues, but there may be something in some printer/program
      drivers that deliberately messes with the image (making
      counterfitting not so easy?).

      A similar effect is that many photocopiers slightly magnify the image
      that is supposedly being copied 1:1 so that the document image
      doesn't have that shadow border on the edges (and enlargement doesn't
      match for both axis). So yes, there are difficulties with toner
      transfer methods.

      I just have a hard time justifying $150-200 for a single board that
      is complex enough to not want to hand draw, while being only for
      myself. Sure, one can sell off the extra "free" boards to recoup some
      of the expense, but that implies that what I'm building is something
      others will want (bad enough to pay me $'s for a board).

      If cost were not an issue, I would do a 2/4 layer board with mask &
      silkscreen every time I did a home circuit project. I'm a stickler
      for precision and accuracy most of the time, and a professionally
      produced PCB is a wonderful thing. But I'm not doing projects that
      can justify *that* much cash outlay since they are not commercial
      projects with a positive RTI factor.

      As for drilling, I find that I have a hard time keeping the bit from
      wandering much more than the pad placement accuracy! I think I need a
      drill press and some industrial carbide drills... ;-)

      The point here is that as we move away from the core ELF CPU to add-
      ons, the likelihood of sharing the expense with others drops off
      rapidly. Look at the wide-ranging directions of the disk/offline
      storage discussion. Almost everyone had a different preferred way of
      implementing expansion.

      I simply mentioned the TTS technique since I have observed in the
      various threads some angst about cost for more complex construction
      projects for some of the group members. Funds are usually tighter
      than spare time for our hobby interests.

      And every time you do a design change/revision turn on PCB's, it's
      another hit in the pocketbook to the tune of many

      I personally don't like a lot of "blue wires" on a PCB (kind of
      defeats the idea of preprinted circuits). I figure that a PCB project
      shouldn't look like a wire-wrap project when it's done. So, if I have
      to do some major modifications, I'd like to be able to make some
      design changes and clean up the board if possible, thus ending up
      with a pretty version once I get the bugs worked out. But that will
      be expensive if the board is somewhat large and done by a commercial
      board house.

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