PCB Designing,Auto Place & Auto Route

Discussion in 'General Electronics Chat' started by rahdirs, Jun 28, 2013.

  1. rahdirs

    Thread Starter New Member

    May 22, 2013
    I have designed a circuit during my internship.I'm new to PCB designing as they don't even teach it in university.

    I've gone around some Cadsoft Eagle Tutorials,but i still feel it uncomfortable,so i thought of trying to design some PCBs,no matter how bad they are.

    The software that i use UltiBoard,gives an option for Autoplacing & Autorouting.
    Then why do i need to custom design them ????

    I also saw in Ultiboard's manual which describes the way it does Autoplace & Autoroute which looks good(Maybe it appears good to me).

    Why don't ppl use Autoplace & Autoroute then??
    This is one PCB board i generated that way
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    In general, autorouters do not give results that are as good as layouts done manually by skilled designers. The technology is improving, and will continue to improve.

    In the example you posted, there are numerous places for changes that would improve the layout. For example, the traces seem very small, especially those going to the power transistors.
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    Autoplace, I would NOT use it. A human can do the placement much much better. Autorouter nah...for such a small project the human brain is again much better.
    From your draft I can see you have much to learn(indeed). I would not show this to your supervisor at all. As a start maybe this document may help you out some http://alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf
    The first I would comment on your board is track width. The more current the wider track you need. The tracks on your TO3 type components(http://www.siliconfareast.com/to-types.htm) is probably way to thin. Second TO3 components most often conduct a lot of current. So they will heat up. And has to be mounted on heat sink. I recommend telling us what your circuit is meant to do. For design inputs.
    Anyway learning is a process we all have to go through. So do not worry about that. And good PCB design is not learned over night. And I am sure this forum will be able guide you. Your board has for sure other issues but. but let us leave them for now.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    autoplacement = no In designing not just the PCB but the product it goes into there is always a need to have specific connectors in specific spots,etc.. Then you always want certain components as close to IC's,etc.. autoplacement (in the program I use anyways) just treats each component identical and just places in a "grid" pattern and its never right.. The ONLY time I use autoplacement is with the "outside board outline" option just to clean up the initial placement. It just spreads all the parts around the board outline in a clean organized fashion.

    autorouter = yes I use it ALL the time.. But whats been said above is true.. The autoroute algorithms just aren't 100% yet. But getting very close. I usually autoroute 75% of the traces and manually do the rest.

    Before we had a PCB program I actually designed/laid out all circuit boards in Autocad. Manual trace routing would/could take me 2-3 days or more back then.. Now the same board (redrawn in my pcb program) took 20 seconds to autoroute. Then I simply go back and manually adjust/clean up the traces where needed.
  5. Razor Concepts

    Senior Member

    Oct 7, 2008
    The autorouted circuit in the first post isn't very good, the traces are too small.

    My opinion is that Eagle has a terrible autorouter, so I manually route all traces. I get much more compact and better routed boards.

    I've used Altium Designer before, however, and that autorouter is amazing. I have a huge 4-layer board, and I do what mcgyvr does - route 25% of the traces (usually important ones, sensitive ones, etc), then click autoroute and then it works its magic.
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Autoplace? Never seen it, would be dubious it would actually work. Typically I already have an idea how the circuit looks, so I just slide around the footprints (with lock to grid ON) until I like the arrangement. Airwires helps put things that should be be next to each other next to each other.

    Routing comes into two broad categories: special things like power traces that need to be wide (up to a solid board size plane) or things that need to be close together or far away, or "other." The other category is "just connect em any ole way."

    Autorouters are great at the second type. So hand route the critical traces before you sun a router.
  7. nigelwright7557

    Distinguished Member

    May 10, 2008
    I use a swap position auto-placer.
    This swaps the position of two components if it gives an improvement in the net length.
    This is an example of something a computer is good at.