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Thread: Eagle ERC questions
face picon face BY : email (remove spam text)(Olin Lathrop)

kbenEraseMEspamspamdca.net wrote:
> I basically have five net classes in Eagle v5.1
> signal,gnd20,gnd40,pwr20, and pwr40.
> The gnd20 goes to the logic chips, and the gnd40 goes to the
> motor control chip.

You are confusing net classes with the net name.  Each net can only have one
class and one name.  You can't assign one class to a part of a net and
another to the rest.

I usually use one of two solutions.  The first is to manually route critical
parts of nets.  You probably want to do this anyway if you need large
current capability since you don't want those tracks going all over the
place and you want to keep the current loops to a minimum and you have to
carefully think about ground offset voltages.  You can manually route with
any width and drill size regardless of the net class.  I usually manually
route all ground connections because I usually have a ground plane or pseudo
ground plane.  In those cases, I want each ground SMD pad with its own via
straight to the ground plane.  This is usually better for the signals and
makes subsequent routing easier.

The second method is to break up a logical net into multiple Eagle nets by
using "short" devices.  These are just copper with two connections.  I draw
them as a slightly thickened line on shematics.  To Eagle each side of the
short will be a different net.  This technique is particularly useful to
guarantee that the ground connection for some part of the circuit connects
at exactly one point that you can place to the rest of the circuit.  This
allows you, for example, to keep switching power supply loop currents
isolated and off the main ground plane.

Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.
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See also: www.piclist.com/techref/pcbs.htm?key=eagle
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