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Ground planes and Reopening .brd file.

Former Member

I read in several places on the net that when making a proper ground plane using a polygon, when the .BRD file is closed and reopened, the polygon is lost.

 

Is this still true in the latest versions? If I call my polygon GND it tries to connect it to every GND point. That's silly. If I call it anything else it won't connect to ANY GND points, which is sillier still. I can get round it, but when I send the file off to the board makers, all the polygons revert and have to be recreated.

  • 0

    If you create any polygon with any signal name, then it will connect to all the pins which are connected to the net with that signal name.

    Why do you think that is silly? Why would you not want your ground pins connected to the ground plane? I don't understand.

     

    If you create a polygon with no name which matches any other signal name, why is it silly that it does not connect to any signals?

     

    To my thinking (and, I'd suggest, the majority of users) both situations are expected behaviour.

     

    Secondly, when you close and re-open the board the polygons are not filled, but they still exist as fully poured polygons, only their outline is shown. Believe me, you will come to live by this very useful feature.

    If you type 'rats' or hit the ratsnest button the polys will be shown as filled - until the next time you open the board file - but remember, they ARE still filled polys, they are only shown as outlines to make working on the board easier.

  • 0 in reply to KennyMillar
    Hi Kenny, thanks for your reply:
    "If you create any polygon with any signal name, then it will connect to all the pins which are connected to the net with that signal name. Why do you think that is silly? Why would you not want your ground pins connected to the ground plane?"
    Because it creates  tiny loops which can have a huge effect at 8GHz. I know where it should be connected, Eagle doesn't. It should NOT be connected at every point. It should be connected where I tell it to be connected. Further, I need to star earth one layer and use a ground plane for other parts. Eagle won't let me do that. That's why it is silly. Clearly the people who wrote it are not electronic engineers.
    "If you create a polygon with no name which matches any other signal name, why is it silly that it does not connect to any signals?"
    I didn't say that. I  said it won't LET ME CONNECT IT. Which it should. I know what I want it connected to. Eagle doesn't. And when I reopen the .brd file I have to manually do this again and, worse, the board house has too as well (and I can't easily see what they've done).
    Regards
  • 0 in reply to Former Member

    It is just one polygon per netname. You could make several polygons, for example GND, AGND, PGND and more. If it is that clear to you that nets must be sperated, then it would also be clear to indicate in your electronic diagram by using different net names.

    For the critical places you could also draw normal pcb tracks.

  • 0 in reply to Former Member

    Thanks Patrick. I understand what you mean, also got answered in the other thread by Jorge http://www.element-14.com/community/message/13552#13552

     

    It sort of works, but is confusing. But now I see what I must do, I will find a way of it doing EXACTLY what I want.