Re: gEDA-user: Two pin variable capacitor symbol with 3 pin footprint

[Steven Michalske <smichalske@xxxxxxxxx>]

On Apr 20, 2009, at 11:02 AM, Stefan Salewski wrote:

> On Mon, 2009-04-20 at 10:34 -0700, Steven Michalske wrote:
>> On Apr 20, 2009, at 3:20 AM, Stefan Salewski wrote:
>>
>>> On Mon, 2009-04-20 at 12:06 +0200, Stephan Boettcher wrote:
>>>
>>>>
>>>> - use the 3-pin footprint and connect pin three with a net=  
>>>> attribute
>>>> on the symbol
>>>>
>>>
>>> This idea in not new to me, I tried something similar with an OpAmp
>>> with
>>> multiple power pins -- now i prefer a special footprint.
>>>
>>> I have 8 of these variable capacitors (8 and 10mm diameter), so I  
>>> have
>>> to give the first symbol a net attribute like "net=CapVarNetA:1,3"  
>>> the
>>> next "net=CapVarNetB:1,3" the next "net=CapVarNetC:1,3" then next...
>>>
>>> A gschem pin which can have multiple pinnumbers may be a nice
>>> solution?
>>>
>>
>> I like the idea of a delimited list of pins for a pin.
>>
>
> I too.
>
>> I dislike the net attribute, is seems like a hack and doesn't allow
>> for changes easily.  changing the net name of the net feeding that  
>> pin
>> won't be quite what you want.
>>
>
> I think the same.
>
>> My solution for this problem is to make a new symbol, and explicitly
>> place all pins.
>>
>>
>
> No. A capacitor with 3 pins in a schematic?
> Just because some devices have 3 pins for technical reasons? I think a
> symbol in a schematic should be abstract, and a capacitor is a two pin
> device from its physics.
>
> I started with special footprints with pin 3 renamed to 1, DJ suggests
> this too, so I go on using it. The only minor problem is, that I  
> have to
> keep my footprints sorted, I have to care that I newer use such a
> modified footprint when I really need 3 pins, i.e. for a  
> potentiometer.
> My current solution: Have general 3 pin devices, with a local (not
> public) copy with pin 3 renamed to 1. I was not able to find a nice  
> name
> to this modified copy, so I append @2. This should remember me. Now I
> have true three pin devices named i.e.
> TRIM_TB_3N_1000D__Sprague-Goodman_Spec-1.fp
> and the special, local copy named
> TRIM_TB_3N_1000D__Sprague-Goodman_Spec-1@xxxx
>

Until gEDA can handle the fact that one electrically connected pin  
represents multiple physical pins in without overloading an attribute  
not meant for it,  I will use a symbol with three terminals.

This is also due to the fact that not all designs want both pins  
connected, yes a corner case, but still valid.

I agree that the schematic should be symbolic,  but multi pin/net  
needs some help.

I believe there was an extensive thread about this where we discussed  
pin groups and the like, but nothing came to fruition.

> Best regards
>
> Stefan Salewski
>
>
>
>
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