Newbie: Off-grid SMT components

Kerry S. Martin schrieb:

Hello,

I have recently started using Eagle.  I am trying to place 0805

components and am having a problem because the pads in the standard

library are off of the grid (50 mil).  If I place the component

horizontally and then try to route a trace from the side of the

component, the trace does not exit the center of the pad but instead the

trace is aligned to the grid and is offset from the center of the pad.

The only way I can get it to work is to use a very fine grid.

 

However, if the component is rotated vertically a trace exits from the

center of the pad even if the pad is off grid.

 

Thank you,

Kerry

Yes, the TRH are in inch and the SMD are in Millimeters, so the grid

"never fits". Anyway, choose the grid you want to work with. Eagle has a

"grab" function that works in such a way that if you start routing close

to a pad, the center of the pad will be grabbed even if that is off grid.

Your rounting then continues on the choosen grid. To connect to a

different part, you stop the routing a little before reaching that part

and start new from the pad of the other part, so the "grabbing" can take

place again.

In other words, if you have mixed mm/mil layouts allways route away from

the parts.

--

Gruß

Jörn

How do you actually do this? Do you work with a script or can it be done by

invoking the autorouter and the gui?

"Joern Paschedag" <jpaschedag@t-online.de> wrote in message

news:ge1siv$p7b$1@cheetah.cadsoft.de...

Kerry S. Martin schrieb:

Hello,

I have recently started using Eagle.  I am trying to place 0805

components and am having a problem because the pads in the standard

library are off of the grid (50 mil).  If I place the component

horizontally and then try to route a trace from the side of the

component, the trace does not exit the center of the pad but instead the

trace is aligned to the grid and is offset from the center of the pad.

The only way I can get it to work is to use a very fine grid.

 

However, if the component is rotated vertically a trace exits from the

center of the pad even if the pad is off grid.

 

Thank you,

Kerry

Yes, the TRH are in inch and the SMD are in Millimeters, so the grid

"never fits". Anyway, choose the grid you want to work with. Eagle has a

"grab" function that works in such a way that if you start routing close

to a pad, the center of the pad will be grabbed even if that is off grid.

Your rounting then continues on the choosen grid. To connect to a

different part, you stop the routing a little before reaching that part

and start new from the pad of the other part, so the "grabbing" can take

place again.

In other words, if you have mixed mm/mil layouts allways route away from

the parts.

 

 

--

Gruß

 

Jörn

Jörn,

Thank you for your helpful answer.  I have found that if I use a wire

bend of 1 to start on a component, and 3 to end on a component, that the

"grab" function that you described gives me the result that I want.  If

I have two components side-by-side and I want a trace directly from the

center of one pad to the center of the other, I use a wire bend of 2 and

it produces the desired result.

Thank you so very much,

Kerry

Joern Paschedag wrote:

Kerry S. Martin schrieb:

Hello,

I have recently started using Eagle.  I am trying to place 0805

components and am having a problem because the pads in the standard

library are off of the grid (50 mil).  If I place the component

horizontally and then try to route a trace from the side of the

component, the trace does not exit the center of the pad but instead

the trace is aligned to the grid and is offset from the center of the

pad. The only way I can get it to work is to use a very fine grid.

 

However, if the component is rotated vertically a trace exits from the

center of the pad even if the pad is off grid.

 

Thank you,

Kerry

Yes, the TRH are in inch and the SMD are in Millimeters, so the grid

"never fits". Anyway, choose the grid you want to work with. Eagle has a

"grab" function that works in such a way that if you start routing close

to a pad, the center of the pad will be grabbed even if that is off grid.

Your rounting then continues on the choosen grid. To connect to a

different part, you stop the routing a little before reaching that part

and start new from the pad of the other part, so the "grabbing" can take

place again.

In other words, if you have mixed mm/mil layouts allways route away from

the parts.