[geda-user] Surrounding a component with an island of non-ground

[Richard Hughes]

Hi all,

I'm designing a double sided PCB that has two giant rect acting as a
ground planes on both sides, with traces hand-drawn for the signals.
This works well from an EMI point of view for the digital logic on the
board. I'm now adding a photodiode array and 24 bit ADC (down to 20nA
input current) , and want to surround all the signal traces from the
array to the ADC in an island of common cathode, to avoid any leakage
currents.

I'm able to join traces to the ground plane using "j", but I'm not
able to work out how to "join" an island of a polygon to a random
signal. I guess I'm trying to ask how to "join" random lines with
random polygons, without drawing a complex digital ground polygon
around the photodiode array. Ideas very welcome, thanks!

Richard

[miloh]

Look for the menu item: new lines, arcs clear polygons. Perhaps this is the
behavior you are looking for to connect the rects and polys to traces.

It's described more in various tutorials, like the following:
http://hobby-electrons.sourceforge.net/tutorials/gEDA/index.html

Post by Richard Hughes
Hi all,
I'm designing a double sided PCB that has two giant rect acting as a
ground planes on both sides, with traces hand-drawn for the signals.
This works well from an EMI point of view for the digital logic on the
board. I'm now adding a photodiode array and 24 bit ADC (down to 20nA
input current) , and want to surround all the signal traces from the
array to the ADC in an island of common cathode, to avoid any leakage
currents.
I'm able to join traces to the ground plane using "j", but I'm not
able to work out how to "join" an island of a polygon to a random
signal. I guess I'm trying to ask how to "join" random lines with
random polygons, without drawing a complex digital ground polygon
around the photodiode array. Ideas very welcome, thanks!
Richard

[Jason White]

IIRC, putting a via on the end where you would like to join the plane
and the trace and then using the thermal tool "change thermal type"
(shift+left click with thermal mode selected I believe) will do it.
That should join the via to the plane so the trace will be connected
to the plane where it overlaps the via. The signal shouldn't need to
actually go through the via, the via is just sits there stitching the
plane to the trace.

Post by miloh
Look for the menu item: new lines, arcs clear polygons. Perhaps this is the
behavior you are looking for to connect the rects and polys to traces.
http://hobby-electrons.sourceforge.net/tutorials/gEDA/index.html

Post by Richard Hughes
Hi all,
I'm designing a double sided PCB that has two giant rect acting as a
ground planes on both sides, with traces hand-drawn for the signals.
This works well from an EMI point of view for the digital logic on the
board. I'm now adding a photodiode array and 24 bit ADC (down to 20nA
input current) , and want to surround all the signal traces from the
array to the ADC in an island of common cathode, to avoid any leakage
currents.
I'm able to join traces to the ground plane using "j", but I'm not
able to work out how to "join" an island of a polygon to a random
signal. I guess I'm trying to ask how to "join" random lines with
random polygons, without drawing a complex digital ground polygon
around the photodiode array. Ideas very welcome, thanks!
Richard