Thanks, I had completely forgotten about those situations where a ground
plane isn't being used...

There are several ways that I can think of to do this, if you give the
router info on the maximum size of the current through the connection, and
the maximum voltage drop across the connection (implied as 0.1V otherwise)
then it will attempt to route the connection such that it always remains on
the low side of the threshold, ie the track will be < X ohms in resistance
over its length and the track throughout the route would be capable of
handling the input current.  This means that other tracks would be routed in
perhaps a slightly longer route depending on the priority of that particular
track with reference to the large power bus...

This would require setting up priorities for different connections however,
something which can be a little time consuming...

Thanks for the feedback guys, I'll have a think about all these problems and
will eventually get something worked out about them...

----- Original Message -----
From: "David VanHorn" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Thursday, October 17, 2002 5:31 AM
Subject: Re: [PEDA] OT: DIY: autorouter

> It might be interesting to consider the board as an array of spots, and
route each track separately, noting which spots get used the most. Then use
that data to cause the longer tracks through those points to flee those
points. They are already long, making them a bit longer usually won't hurt.
> When I manually route, I try to get all the critical stuff in first, then
the short stuff, then progressively longer tracks, looking for groups of
signals that can be routed together.
> One thing that's hard to do in autorouters, is to consider return current.
Current project: I have this printhead, that will take pulses of up to 10A,
and dump them into "ground".  Obviously I would prefer that current route
back to the source cap on a dedicated track, but every AR I've ever seen
would cheerfully dump it into the plane, and let it meander the entire board
before getting home.
> In order to handle this, you'd have to have a way to flag a net as "high
current", and to tell the system where it's source is.
> Stuff like this, is why I almost never autoroute. By the time I could get
done setting up all the conditionals and fencing in the AR, I could have
routed it myself.

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