Re: gEDA-user: co-ordinates PCB

["richard.bown@xxxxxxxxxxxxxxxx" <richard.bown@xxxxxxxxxxxxxxxx>]

Stefan Salewski wrote:
> On Tue, 2009-03-31 at 14:46 +0100, richard.bown@xxxxxxxxxxxxxxxx wrote:
> 
>> Sorry
>> I must be getting a bit thick in my old age, are you saying that in the 
>> second quandrant, ie where the first quadrant is between 0 degrees and 
>> 90 degs, and the second quadrant is between 90 degs and 180 degs, that y 
> 
> Coordinates do not depend direct on quadrant.
> 
> x increases to the right.
> 
> y increases to the bottom.
> 
> 0,0 is top left for pcb boards.
> 
> footprint/elements may have 0/0 at different positions, center or at a
> pin.
> 
> Have you seen the verbose
> http://www.brorson.com/gEDA/land_patterns_20070818.pdf
> and my short description
> http://www.ssalewski.de/PcbFootprintRef.txt
> 
> To your capacitor footprints:
> 
> They are rectangular, so its very easy to make them with my sfg script,
> I will make it this evening. If you have Ruby installed you may do it
> yourself. I was already going to make them, but I have seen a minimal
> difference in your dimensions and dimensions on datasheet -- have you
> measured it instead of using dimensions from datasheet? I will check
> this in more detail this evening, the rest takes only a few minutes.
> 
> I think a working cap is on my page, WIMA. Pitch is right, shape may be
> wrong by one mm, this is no big problem. Seems that displaying the shape
> graphical does not work correctly at gedasymbols currently. 
> 
> Best regards
> 
> Stefan Salewski
> 
> 
>
Thanks Stefan its starting to become clearer now, I'd found the 
shortened version, and the PCB handbook which I've printed out.
Being a RF engineer my brain has got used to working with Cartesian 
co-ordinates hence the confusion. Its still a bit confusing as the 
Handbook uses positive co-ordinates and examples in the Brorson docs, 
and footprints on your site use negative co-ords.

As for the dimensions for the capacitors, I took the lead diameter and 
pitch from the data sheets I took the physical dimensions off the 
component, so that would account for any small differences.
Many thanks for the help

-- 
Best wishes

Richard Bown

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