Capacitance sensing pads

LGR wrote:

I'm trying to make some symbols to use as capacitive sensing buttons for use

with a Cypress PSoC Capsense chip. The Cypress application note (AN2292)

says to fill ground around the pads. I can't figure out how to create a

buffer area to keep the polygon from filling right over the pads. Any ideas?

 

 

If the pads are made using SMD pads or through-hole pads, any polygon

drawn around them but named differently from the signals on the pads

will automatically have an isolation space around the pads.

If you draw the touch pads using polygons, you will just have to be

careful how you draw the ground polygon outline so an isolation space is

left.

John G.

John Giddy wrote:

LGR wrote:

I'm trying to make some symbols to use as capacitive sensing buttons

for use with a Cypress PSoC Capsense chip. The Cypress application

note (AN2292) says to fill ground around the pads. I can't figure out

how to create a buffer area to keep the polygon from filling right

over the pads. Any ideas?

 

If the pads are made using SMD pads or through-hole pads, any polygon

drawn around them but named differently from the signals on the pads

will automatically have an isolation space around the pads.

If you draw the touch pads using polygons, you will just have to be

careful how you draw the ground polygon outline so an isolation space is

left.

John G.

If using two polygons then the inner polygon needs to have a lower rank than

the outer. See Help polygon, where there are a few lines on Rank.

  You do not need to take special care about drawing the outer polygon.  The

isolation will be set depending upon the isolation value of the polygons,

the higher value being used.

cheers

David

I guess I wasn't clear. The symbol consists of a through-hole pad (which is

what the device connects to on the bottom layer), and a polygon around it.

The polygon has to be made in the top layer only, because that's where the

touch sensing happens. I can't make it with layer 17, because that would

create polygons on both top and bottom. For the buttons, I suppose I could

distort an SMD, but I also need to create W-shaped elements for the

"slider". If you're curious, here's the application note:

http://download.cypress.com.edgesuite.net/design_resources/application_notes/contents/capacitance_sensing___layout_guidelines_for_psoc_capsense___an2292_12.pdf

"David Moodie" <dgmoodie@onetel.com.cut_this_off> wrote in message

news:g2qoqd$phh$1@cheetah.cadsoft.de...

John Giddy wrote:

LGR wrote:

I'm trying to make some symbols to use as capacitive sensing buttons for

use with a Cypress PSoC Capsense chip. The Cypress application note

(AN2292) says to fill ground around the pads. I can't figure out how to

create a buffer area to keep the polygon from filling right over the

pads. Any ideas?

 

If the pads are made using SMD pads or through-hole pads, any polygon

drawn around them but named differently from the signals on the pads will

automatically have an isolation space around the pads.

If you draw the touch pads using polygons, you will just have to be

careful how you draw the ground polygon outline so an isolation space is

left.

John G.

 

If using two polygons then the inner polygon needs to have a lower rank

than the outer. See Help polygon, where there are a few lines on Rank.

You do not need to take special care about drawing the outer polygon.

The isolation will be set depending upon the isolation value of the

polygons, the higher value being used.

 

cheers

 

David

If using two polygons then the inner polygon needs to have a lower rank

than the outer. See Help polygon, where there are a few lines on Rank.

You do not need to take special care about drawing the outer polygon.

The isolation will be set depending upon the isolation value of the

polygons, the higher value being used.

 

cheers

 

David

LGR wrote:

> I guess I wasn't clear. The symbol consists of a through-hole pad

(which is

> what the device connects to on the bottom layer), and a polygon

around it.

> The polygon has to be made in the top layer only, because that's

where the

> touch sensing happens. I can't make it with layer 17, because that would

> create polygons on both top and bottom. For the buttons, I suppose I

could

> distort an SMD, but I also need to create W-shaped elements for the

> "slider". If you're curious, here's the application note:

>

>

http://download.cypress.com.edgesuite.net/design_resources/application_notes/contents/capacitance_sensing___layout_guidelines_for_psoc_capsense___an2292_12.pdf

I'm not sure that you read his post correctly, he's just saying to

change the rank of the key polygon to be lower than the ground

polygon. Not the layer or anything else. More information can be found

by typing "help polygon" in the command area of the editor like David

mentioned.

Edward

LGR wrote:

I guess I wasn't clear. The symbol consists of a through-hole pad (which is

what the device connects to on the bottom layer), and a polygon around it.

The polygon has to be made in the top layer only, because that's where the

touch sensing happens. I can't make it with layer 17, because that would

create polygons on both top and bottom. For the buttons, I suppose I could

distort an SMD, but I also need to create W-shaped elements for the

"slider". If you're curious, here's the application note:

 

http://download.cypress.com.edgesuite.net/design_resources/application_notes/contents/capacitance_sensing___layout_guidelines_for_psoc_capsense___an2292_12.pdf

 

Avoid top posting in newsgroups- the threads don't make sense that way.

OK I guess it wasn't too clear to me. But here's my second guess.  You

actually want to make a package in the library?  The libraries do not handle

polygons well.

My first guess was that you were just going to draw this straight on the

PCB, which is where polygons of different rank make drawing this relatively

straightforward.  If you want more than one pad, then use copy-cut and paste

for the polygons

cheers

David