kicad-lib-committers team mailing list archive

[Carl Poirier <carl.poirier.2@xxxxxxxxx>]

On Sat, Apr 5, 2014 at 4:28 AM, Kerusey Karyu <keruseykaryu@xxxxx> wrote:

> W dniu 03.04.2014 02:24, Carl Poirier pisze:
>
>
>  About pin length, what about using SI units?
>>
>>  At this point, we shall to ask: How many users use SI units when drawing
> schematics? Most of them will look at grid only and doesn't care about mm
> or inches.
> Units of measurement are important, but where they are actually required
> to maintain strict dimensions.
>

If you look at the metrication of the world, you will notice people using
the imperial system are getting scarce these days.
http://en.wikipedia.org/wiki/File:SI-metrication-world.png


>
>

>  Symbols:
>>
>> 1. A pin length of 4mm is used, except for components without pin
>> numbers which use 2.5mm.
>>
> >
> If we force 4mm or 2.5mm of pin length these pins will be outside of the
> grid when somebody uses inches. IMO this is not the way we should follow.
>
>
Same can be said when one uses the SI system to draw his schematic.


>
> > Footprints:
> > (...)
>
>  2. Pad 1 is placed at the top left corner
>>
> >
> (...) unless the manufacturer places the components in a different
> orientation in tubes, tapes or trays (Important for P&P).


Good point. Can you tell me, for a device that's made by many manufacturers
and sold in such packages, do they all use the same orientation?


>  3. For through-hole components, origin is set on pad 1.
>>
> > 4. For surface-mount devices, origin is placed in the middle of
> > the chip.
> >
> There are also machines for automatic insertion of THT components, so
> mandatory putting origin point at pad 1 is a bad idea.
> We can assume to put origin at pin 1 when we are sure that this component
> will be inserted manually, for example terminal blocks.
>
>
Jean-Paul Louis was telling me that "By convention, the through hole IC
were referenced to the pin one because of the insertion machines." So this
isn't always the case?