Doubling up tracks on different layers

On 4/1/2010 12:23 PM, Michael Sansom wrote:

David Ingebretsen wrote:

Michael Sansom wrote on Thu, 01 April 2010 09:24

Guys,

 

I've got a problem I hope someone can help me out with. I have some

very high current traces on my PCB (15A and 30A). I'm using 2oz copper

 

but in order to get track widths that aren't completely ridiculous I

need to double up the tracks on two layers. I'm new at Eagle (last

used OrCAD PCB editor which is a stripped down version of Allegro)

and I can't seem to make this happen. When I route the initial track

on the

 

first layer naturally the ratsnest for this route disappears (since it

 

is now connected). Eagle won't allow me to start a track on the second

 

layer because there is no longer an active ratsnest. How do I get

around this?

 

This is also a generic issue. If I want to start routing on a pin that

 

the ratsnest currently isn't touching (but it is unrouted, the ratsnest

 

is just terminated on a different unrouted pin) Eagle won't let me.

This is different from Allegro where I could start routing on any pin

and if it was unrouted the ratsnest would immediately snap to that pin.

 

This is somewhat annoying since it is forcing me to route nets in the

 

order that Eagle decides to snap the ratsnest to instead of routing in

 

the order that is most logical to me. I'm sure there is a way around

this, but I've yet to find it.

 

Thanks,

 

Michael

 

I can't help on the first issue, but for the second one, press and hold

ctrl when you are starting your trace and you can start at any

location on

the net.

Also, remember, too, you can press down alt as well to use the alternate

grid spacing temporarily.

 

DAvid

 

Thanks to both of you. Yes, I use the ALT key a lot to switch to my

minimum grid spacing and that works well but I wasn't aware of the CTL

key allowing me to start a line on a pin/pad that wasn't terminated in a

ratsnest line.

 

That first question is really important. The ability to run the same

track on different layers is a key ability when doing layouts with high

current nets. Doug seems to imply that using CTL might work in that

situation as well. I'll try it and see what happens.

 

Moving from one layout package to another is always a pain as you get

trained to think in terms of whatever package you have the most

experience with. After using Eagle for a week or so it seems that there

are many fine attributes of this package. The ability to alter a

schematic and have the results show up immediately in the pcb layout

package is a huge plus. And in terms of pure execution speed it seems

faster than Allegro in many places. However, there are a few things that

I really miss. Allegro would let me constrain my tracks to be purely

orthogonal with 45 degree bends, and would automatically keep tracks

vertical/horizontal as you routed across the board. Also, it would

enforce spacing requirements in real time as you routed a trace (so you

didn't find out that you have tracks closer than your design rules

permit only after running a DRC).

 

All and all it is a very good value. However, I would think that with

the addition of a few key features it could compete with anything out

there. Would be interesting to know what sort of features are on the

road map for future releases.

 

-Michael

 

 

You don't need to route on the second layer, just draw the copper with

WIRE or POLYGON and name it to the net it should belong to.

Another option which is a little dangerous would be to move the routed

track to a new layer and include that layer in both the top and bottom

Gerbers.

On 4/1/2010 12:23 PM, Michael Sansom wrote:

David Ingebretsen wrote:

Michael Sansom wrote on Thu, 01 April 2010 09:24

Guys,

 

I've got a problem I hope someone can help me out with. I have some

very high current traces on my PCB (15A and 30A). I'm using 2oz copper

 

but in order to get track widths that aren't completely ridiculous I

need to double up the tracks on two layers. I'm new at Eagle (last

used OrCAD PCB editor which is a stripped down version of Allegro)

and I can't seem to make this happen. When I route the initial track

on the

 

first layer naturally the ratsnest for this route disappears (since it

 

is now connected). Eagle won't allow me to start a track on the second

 

layer because there is no longer an active ratsnest. How do I get

around this?

 

This is also a generic issue. If I want to start routing on a pin that

 

the ratsnest currently isn't touching (but it is unrouted, the ratsnest

 

is just terminated on a different unrouted pin) Eagle won't let me.

This is different from Allegro where I could start routing on any pin

and if it was unrouted the ratsnest would immediately snap to that pin.

 

This is somewhat annoying since it is forcing me to route nets in the

 

order that Eagle decides to snap the ratsnest to instead of routing in

 

the order that is most logical to me. I'm sure there is a way around

this, but I've yet to find it.

 

Thanks,

 

Michael

 

I can't help on the first issue, but for the second one, press and hold

ctrl when you are starting your trace and you can start at any

location on

the net.

Also, remember, too, you can press down alt as well to use the alternate

grid spacing temporarily.

 

DAvid

 

Thanks to both of you. Yes, I use the ALT key a lot to switch to my

minimum grid spacing and that works well but I wasn't aware of the CTL

key allowing me to start a line on a pin/pad that wasn't terminated in a

ratsnest line.

 

That first question is really important. The ability to run the same

track on different layers is a key ability when doing layouts with high

current nets. Doug seems to imply that using CTL might work in that

situation as well. I'll try it and see what happens.

 

Moving from one layout package to another is always a pain as you get

trained to think in terms of whatever package you have the most

experience with. After using Eagle for a week or so it seems that there

are many fine attributes of this package. The ability to alter a

schematic and have the results show up immediately in the pcb layout

package is a huge plus. And in terms of pure execution speed it seems

faster than Allegro in many places. However, there are a few things that

I really miss. Allegro would let me constrain my tracks to be purely

orthogonal with 45 degree bends, and would automatically keep tracks

vertical/horizontal as you routed across the board. Also, it would

enforce spacing requirements in real time as you routed a trace (so you

didn't find out that you have tracks closer than your design rules

permit only after running a DRC).

 

All and all it is a very good value. However, I would think that with

the addition of a few key features it could compete with anything out

there. Would be interesting to know what sort of features are on the

road map for future releases.

 

-Michael

 

 

You don't need to route on the second layer, just draw the copper with

WIRE or POLYGON and name it to the net it should belong to.

Another option which is a little dangerous would be to move the routed

track to a new layer and include that layer in both the top and bottom

Gerbers.