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Thread: GW-12887-1: A DS1287/DS12887 et al. Replacement

  1. #1
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    Default GW-12887-1: A DS1287/DS12887 et al. Replacement

    By request, and because I too have a few that need replaced:



    You bend up the legs on a DS12885 (the bare IC used inside the DS12887 module), glue my little board on top, and solder the leads down:



    I had a little 486 ISA industrial SBC that needed a DS12887 replaced, so that was the test candidate:



    Works fine! I need to tweak the castellated holes on the board a bit. There's not enough copper to hold the plated-through hole in, at least for OSH Park's castellation process. I'll release the files once it's ironed out. But, it works, and it'll be easier for hobbyists to assemble than the version that uses surface mount bits. I believe it's cheaper as well -- the DS12885 is cheaper than the surface mount version, and you don't need to acquire module pins since the DIP takes care of that.

    I'll probably do a run of panelized modules and make up a bunch of these, so if people want a fully assembled, ready-to-go version, that's coming.

    One of the best aspects (aside from never having to rework it again!) is that all of the parts are current production and available from e.g. Mouser. No need to have an old IC and tear it down, as with the 48T02/48T08!

  2. #2
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    Quote Originally Posted by glitch View Post
    ...at least for OSH Park's castellation process.
    I was unaware OSH Park officially supported castellation or any form of edge platting? Or is this an unofficial hack?

    Quote Originally Posted by glitch View Post
    ...and you don't need to acquire module pins since the DIP takes care of that.
    It is worth noting Mill-Max makes some nice double tapered break-away headers that work nice for this purpose. I keep bins of them around. But I do like your solution better!

    Very nice project and idea. Thanks!
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

  3. #3
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    Quote Originally Posted by eeguru View Post
    I was unaware OSH Park officially supported castellation or any form of edge platting? Or is this an unofficial hack?
    They support it officially: http://docs.oshpark.com/tips+tricks/castellation/

    It's obviously a little rougher than what you'd expect from a production panel with castellated holes, but it gets the job done for prototypes. Apparently it's somewhat sensitive to the size of the annular ring around what's remaining, I had one of the through-plating sections pop out. So, the new design includes a large rectangular pad that extends well into the board, top and bottom.

    Quote Originally Posted by eeguru View Post
    It is worth noting Mill-Max makes some nice double tapered break-away headers that work nice for this purpose. I keep bins of them around.
    Yep, and Aries makes flat pin DIP headers for a reasonable price, too -- I keep both around for prototyping, I tend to use Batten & Allen pins for production modules, if there's room. The Aries DIP headers have the bonus of being stamped flat pins, much like the Batten & Allen pins. They won't ruin crappy single-wipe sockets.

    Quote Originally Posted by eeguru View Post
    But I do like your solution better!

    Very nice project and idea. Thanks!
    Thanks! I figure it minimizes cost and assembly difficulty for most hobbyists that need to replace only one or two DS12887s and want to make their own boards.

  4. #4
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    Nice work, glitch! But would it be easier to use through-hole pins for the mouting (as mentioned)? Those legs look like a pain to set up.

    The gold-plated breakaway headers are pretty cheap on ebay. I use a lot of them when going PCB-to-PCB.

  5. #5
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    Quote Originally Posted by Chuck(G) View Post
    Nice work, glitch! But would it be easier to use through-hole pins for the mouting (as mentioned)? Those legs look like a pain to set up.

    The gold-plated breakaway headers are pretty cheap on ebay. I use a lot of them when going PCB-to-PCB.
    I just bent them up with needle nose pliers, after the module was glued on, and pressed them into the castellated half-hole in the board. Solder, then trim the end off. I'm not sure it's super clear from the picture, but the rest of the legs are just the IC's normal legs.

    One could of course solder jumpers from the castellated holes to the IC legs.

  6. #6
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    Ah, I was thinking that you were using the TSOP version of the chip. Now things are clear, thanks.

  7. #7
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    Revision 2 prototypes are in and tested!



    Note the large, rectangular pads around the castellated holes. These held the through-hole plating much better than the small annular rings. Should be easier if someone wants to do a toner transfer too!

    Here's a view with the module flipped over:



    You can clearly see it's a DIP chip with some legs bent up from this angle. No headers or pins to line up, just glue the module on top of the DS12885, wait for the glue to cure, then bend the leads up and solder them to the castellated holes.

  8. #8
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    This is a great little idea! I look forward to shoving my money at you.
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  9. #9
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    Me TOO!! Please let us know when and how to order these!!


    Greg

  10. #10
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    I've got these panelized and added to my next PC board order, so they should be in within 2 weeks or so.

    If anyone needs one right now I do have several fully functional prototype modules ready to go.

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