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PCB Layout Designers

Discussion in 'Electronic Design' started by Tom, May 22, 2007.

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  1. Tom

    Tom Guest

    Morning All

    Guess this is really 2 questions, first up.....

    I am still using an old DOS version of EasyPC Pro for PCB layout,
    mainly because they want a stack load of money to upgrade. I did a
    long time ago post a question about free PCB packages, and found one,
    but the problem was that the package really relies on entering the
    schematic first, creating the nets the polishing the layout afterwards
    in PCB mode.

    I don't actually dot he circuit designs, the company is my fathers, he
    designs them, I translate his PCB designs on paper to designs in
    EasyPC for printing out and either home manufacture or for sending of
    for bulk manufacture.

    Does anyone know of an existing package that allows for this approach,
    ie not bothering with the schematic?

    The second question....

    This is kind of related to the first, I'd be interested to know if
    everyone designs their PCB's from the schematic stage upwards on
    computers, or whether there are many people creating the PCB layout
    only?


    Tom
     
  2. OBones

    OBones Guest

    I personally always start with the schematic and then move to the PCB
    just because the PCB tool verifies that I did not leave any connection
    unrouted. And with more than 20 nets, this becomes increasingly
    interesting to have.
     
  3. Paul Burke

    Paul Burke Guest

    Tom wrote:
    I am still using an old DOS version of EasyPC Pro for PCB layout,
    I don't think £447 is excessive for the features you get with the
    complete unlimited version. And by the sound of it, your PCBs could
    almost certainly get away with one of the limited versions.
    You can enter directly to the PCB with EasyPC (always have been able to
    as far as I know), and add the nets manually. Recent versions will
    produce a ratnested schematic from the laid out PCB.
    For anything except trivial PCBs (a resistor and a LED say), it's always
    more secure to start with the schematic. It's much easier to verify. But
    also remember to verify the PCB packages. Never trust your own library,
    let alone someone else's.

    Paul Burke
     
  4. Protel AutoTrax will do exactly what you want, it's now freeware.
    http://www.altium.com/Community/Support/Downloads/

    A lot of people (Hobbyists and one-man-bands mostly) still do the PCB
    only from a handdrawn schematic, but almost no one does that in
    professional circles.

    AutoTrax will even let you generate a netlist from your hand drawn
    PCB, and then you can still do some basic DRC checking.

    Dave.
     
  5. Sure, EAGLE from CadSoft. It comes in three modules -- schematic, board
    editor, and autorouter -- that you can buy seperately. So if you only buy
    the board editor you get exactly the functionality you want.
    Everybody (except your dad) does it in CAD, from schematic upwards. It's
    sooo much easier to maintain consistency between schematic and board. Of
    course many people first draw schematics by hand, but before they go to the
    board stage they'll recreate the schematic in CAD and then do the board in
    CAD as well.

    Remember: If the CAD schematic is correct, there is NO WAY the corresponding
    board could be electrically faulty (i.e., have missing or wrong connections
    between parts) because the CAD package will always ensure 100% consistency.
    Or is anybody aware of a CAD system that doesn't maintain board-schematic
    consistency? That would be something to steer clear of.

    robert
     
  6. Paul Burke

    Paul Burke Guest

    Well most programs have the odd bug now and again. But it does reduce
    the incidence.
     
  7. DJ Delorie

    DJ Delorie Guest

    gEDA's PCB was originally designed to work standalone, and it still
    retains that capability. You can pull component footprints from the
    parts library, connect up pins to form a ratlist, then route it. It
    can even use a scan of a pre-existing board as the background, to act
    as a template for replicating lost designs.
     
  8. Robert Baer

    Robert Baer Guest

    ExpressPCB software allows both approaches; the PCB side does not
    require the schematic, and if you *do* use it, the result is a bit
    clunky - slightly better than a kick in the head (unless there most
    recent update improved matters).
    BUT, the result is that you have them do the boards, typically in
    pairs (2, 4, 6, etc).
    If you want gerbers from their software, forget it.

    I have made pc boards since the early 1970s and always have done them
    "by hand" (first black tape, then blue/red/black, and now via software).
     
  9. Robert Baer

    Robert Baer Guest

    Is it still the case that gEDA will not work in WinDoze?
     
  10. AutoCAD ? A few footprints and you're there.

    Rene
     
  11. It's correct, almost by definition, but there are ways a schematic can
    *look* correct, and not be. That's why (in addition to running DRC, of
    course) I always create a human-readable netlist and give it a decent
    lookover (thanks to, IIRC, John L for this suggestion).



    Best regards,
    Spehro Pefhany
     
  12. DJ Delorie

    DJ Delorie Guest

    gEDA has worked in Windows for a while now.

    We just don't have a pre-built binary for it. But then again, we
    don't have pre-built binaries for Linux either. So, you have to
    figure out how to build and install it yourself. PCB at least comes
    with suitable scripts and readme's for building under Windows.
     
  13. Tom

    Tom Guest

    Sorry, I was not very clear there, yes EasyPC does indeed allow this
    and always has, and although £447 is not that much, for a one man band
    that only uses it occasionally if there were a cheaper or freeware
    version around that oly provided the libraries/gerber/drill and PCB
    design function that would be preferable.

    The designs in question are considerably more complicated than a
    resistor and LED ;-) However a lot of complexity is removed by the
    user of PIC's, and all of them have been made in production releases
    on vero-board before the PCB exists, so the design is is well known by
    my father.

    The final fly in the ointment is that my father is not a computer
    competent person.

    Tom
     
  14. Robert Baer

    Robert Baer Guest

    Maybe for you, but nothing ever works for me the first, second or
    third time.
    And in this case, one would have to somehow get the compilers (wil be
    more than one with my luck).
    Worse, the smallest download will be over 4megs, making it impossible
    (i am on dial-up).
    So, for gEDA, i would need a pre-built binary on CD.

    Net result? gEDA will not work for me.
     
  15. Tom

    Tom Guest

    Yep, the old boy is exactly that, the one man band!

    I was really looking for something was Windows and current rather than
    DOS. Easy PC does the job, but the version we have is an old DOS
    program and the libraries are rather old now.

    Tom
     
  16. Tom

    Tom Guest

    Hmm, this one really raised my hopes, what I failed to indicate was a
    Windows requirement.

    Tom
     
  17. qrk

    qrk Guest

    I've seen Orcad Layout v10.x, on multiple occasions, mung up the net
    list mid way thru the project. It would tie separate nets together. At
    the end of the project, I reimport the netlist just in case Layout did
    something evil.
     
  18. Mike Monett

    Mike Monett Guest

    What kind of errors are you looking for? It sounds like a lot of work, and
    it won't catch mistakes such as typos on part values.

    Maybe it would be better to fix the conditions that lead to the errors in
    the first place.

    For example, .1uf is sometimes hard to read when the decimal is obscured,
    so people usually put a zero in front to clarify: 0.1uf. Others may use "R"
    in place of the decimal, such as 1R5 for a 1.5k resistor.

    I'm sure there are many other ways of doing schematics that help avoid
    mistakes, and developing these good habits can save a lot of time and
    grief. If you can only find 90% of the mistakes, it pays to reduce the
    number in the first place.

    I tend to pick up most things in pcb layout and routing, so for me, a cad
    package that does back annotation is essential. I found trying to do it
    manually is very error-prone:)

    Regards,

    Mike Monett
     
  19. Mostly stuff like hidden connections to supplies that have a variety
    of different names. For example, Vss, GND, Vee, etc. which can form an
    isolated net if there are multiple parts that use the same name, but
    you forget to check the names on every part with hidden power pins and
    make sure it's tied to the proper supply. That would normally get
    caught at layout, but it's better to catch it earlier. Similarly,
    typos on labels could lead to isolated nets with more than one node,
    so that DRC isn't likely going to catch it.
    I prefer to show all the power pins on parts, but sometimes that makes
    the schematic too messy, and that could obscure other problems.
    A number of years ago I was converting a schematic from hand-drawn to
    electronic and was a bit surprised to notice an obvious error. I'd
    fixed it without even noticing in the (manual) layout. Unfortunately,
    computers don't "know what you meant" to draw.


    Best regards,
    Spehro Pefhany
     
  20. Mike Monett

    Mike Monett Guest

    Like you, I prefer to show all the nets on the schematic so they
    light up when you select them. Hidden nets are a recipe for
    disaster.

    I usually end up writing a separate program to assist in naming
    nets, entering proper component values, generating the pin
    connections on new packages, and anything else that is tedious and
    error-prone. Most cad packages have macro capability which makes it
    easy to enter the data, or you can simply paste it into a data entry
    box.

    Anything that reduces the chance for human error is worth
    considering, no matter how small or trivial it may seem.

    A mistake takes only a second. Finding it can take weeks:)

    [...]
    I think the schematic should show everything - unused pins, unused
    sections of ics, power supply filtering, all bypass caps
    (naturally), and anything else that helps understand each connection
    on the board. I usually add separate pages at the end to show all
    this stuff.

    [...]
    Soon, maybe. As mentioned above, I try to add as much as possible in
    a separate data entry program and get it to check the info before
    putting it into the schematic. That saves a lot of time and greatly
    reduces the number of errors.
    Regards,

    Mike Monett
     
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