kicad-developers team mailing list archive

[Jean-Paul Louis <louijp@xxxxxxxxx>]

Hi Andy,

Thank you for your clear reply.

I also worked for more than 40 years in the professional side of electronics,
so I will say that I can be biased by that fact.
I see that you’re using “symbol” and I agree wit that. The schematic use symbols.

In my work life (mostly in two different countries, first France, and then USA), we
used both symbol, component and part.
The symbol was a term used ONLY with the schematic and referred to an electrical function,
the component was the implementation of a symbol with a given technology and package,
and the part was the product you could buy from a list of approved suppliers for that component.

I was working for many years in a group controlling the corporate library, and all three terms
were used but not interchangeably.

As you said, approved vendor/supplier list, and approved part list was a thing designers
were used to, even if sometime they didn’t like it.
But it was the key of a manufacturable and reliable design, and a key to great cost savings too.

To make KiCAD easier to use, maybe a neophyte user should focus more on the part name which
is the thing that can be purchased. But KiCAD does not carry the concept of part which is really
tied to procurement. A part library should be the link between a symbol, a package and a supplier,
but the supplier view is absent in KiCAD library (only a custom field can carry the complete
manufacturing part number), so it is not easy to provide a clear procedure.

Maybe the schematic symbol could be named with the Mfg PN, and then the package would be unique.
That would lead to a huge redundancy in the symbol library, and also in the package library,
which both would have many similar but not identical (ie many similar SO28 from many suppliers).
It is a complex issue, and I am not sure how KiCAD can address it with the current state of design.

Best regards,
Jean-Paul
N1JPL







> On Nov 25, 2017, at 2:32 PM, Andy Peters <devel@xxxxxxxxx> wrote:
> 
> 
> 
>> On Nov 25, 2017, at 10:55 AM, Jean-Paul Louis <louijp@xxxxxxxxx> wrote:
>> 
>> Andy,
>> 
>> I disagree with your statement that component and part are the same thing.
>> 
>> A component is a term used for the generic part, like a 10k resistor, a 7474 digital IC, a 741 op amp, etc..
>> A part on the opposite side is a one to one relationship, unique to a single supplier.
>> 
>> So you cannot mix component and part unless you are a careless designer who does not care about
>> the specifications differences between manufacturers. I have seen too many designs fail when changing supplier.
>> A hobbyist might not care in a one of a kind design, but a professional will test for compatibility
>> of the various sources in extreme cases, like high and low power supply, and temperatures extremes.
> 
> Hi, Jean-Paul,
> 
> I suppose I should preface this by saying I’m a long-time do-it-for-a-living electronics engineer, so I tend to be careful.
> 
> I think perhaps this is a semantic argument with the added joy of language and country-of-origin differences. When I said, “‘Component' and ‘part' are synonymous,” I think you’re right, they’re not specifically the same thing. In context, whether one means “10k resistor” or “10k0 1% 0805 SMD resistor” is clear, as is “op-amp” and “OPA551PA.”
> 
> The situation you describe — the designer who doesn’t care whether a resistor is a 10k 1/8 W through-hole thing or an 0805 or whether 1% or 0.1% or 5% — is indulged by CvPCB and the idea that you can assign a footprint to a component symbol and get a “part” just before layout. That whole idea makes me crazy, it’s so backward, as I’m used to having an approved parts (there’s that word) list, and a company CAD library filled with parts that have footprints, 3D models and part numbers all in place. The idea is simply choose the part, vet it, create a library part once, use it on many designs going forward.
> 
> With that distinction made — “part” is synonymous with “fully qualified atomic part” and “component” is “generic thing,” how is Mario’s original question answered? The symbol library contains symbols, which may be components or may be parts. Again, pick something and document it so everyone is on the same page! (I’m in too many meetings where there are long-winded semantic discussions about things, and when asked my opinion, I say, “I really don’t care, just pick something and tell me what I should do!”)
> 
> How these concepts, not just the words, translate to other languages is something beyond my expertise (I’m monolingual).
> 
> —a
> 
> 
> 
> 
>> 
>> Just my two cents,
>> Jean-Paul
>> N1JPL
>> 
>>> On Nov 24, 2017, at 11:15 PM, Andy Peters <devel@xxxxxxxxx> wrote:
>>> 
>>> 
>>> 
>>>> On Nov 22, 2017, at 7:53 AM, Wayne Stambaugh <stambaughw@xxxxxxxxx> wrote:
>>>> 
>>>> On 11/22/2017 08:42 AM, jp charras wrote:
>>>>> Le 22/11/2017 à 14:28, Marco Ciampa a écrit :
>>>>>> On Wed, Nov 22, 2017 at 08:14:02AM -0500, Wayne Stambaugh wrote:
>>>>>>> The devs discussed this some time ago and the general consensus is that
>>>>>>> symbol is the preferred term.  I've already started converting the UI
>>>>>>> strings to use the term symbol.  I'm sure there are UI strings that I
>>>>>>> missed.  If you find them, please let me know so I can correct them.
>>>>>>> 
>>>>>> 
>>>>>> I think that then there is some term confusion here ...
>>>>>> 
>>>>>> #: eeschema/menubar.cpp:462
>>>>>> msgid ""
>>>>>> "Edit components to symbols library links to switch to an other library link "
>>>>>> "(library IDs)"
>>>>>> 
>>>>>> This obviously is not "symbol to symbol link" ...
>>>>>> 
>>>>>> I really think that we should stick with the terms "footprint" and
>>>>>> "symbol" only, and get rid of all the "component", "part", "module" and
>>>>>> such altogether...
>>>>>> 
>>>>>> TIA
>>>>> 
>>>>> Sure 'This obviously is not symbol to symbol link",
>>>>> but what is the meaning of "symbol to symbol link"
>>>>> 
>>>>> Symbols live in symbol libraries, and components in schematic files, at least for this menu.
>>>>> And currently a symbol does not live in a schematic,
>>>>> and a component has a link (lib id) to the symbol it uses in the schematic.
>>>> 
>>>> I think the terminology should be "library symbol" and "schematic
>>>> symbol".  Both exist but schematic symbols have no graphic items other
>>>> than fields.  The actual graphical representation of the symbol itself
>>>> is a link to a symbol in a library.
>>> 
>>> From a user’s perspective, at least for Mario’s original question:
>>> 
>>> “Component” and “part” are synonymous. At least, this is the consensus over at the kicad.info user forum.
>>> 
>>> That consensus extends to: A component is a symbol which has an associated footprint. This implies that CvPCB is not used, and a component in a symbol library has a valid entry in its Footprint field. When you place a component onto the schematic, it contains everything necessary to use it in the layout.
>>> 
>>> If the symbol in the library has an empty footprint field, it is just a symbol. A user may create a symbol so something might be included in the BOM. A symbol might be created for use with SPICE. The power symbols are just that, symbols.
>>> 
>>> A “fully atomic part” is a symbol with a footprint and some kind of part number information to make it unique. That is, an OPA551PA symbol will have its footprint field filled in with DIP8_300 (or some other 8-pin DIP package) and a custom Part Number field is added and is filled in with something useful for the user.
>>> 
>>> All that said, whatever nomenclature ends up being chosen should be documented so everyone understands what is meant by each term.
>>> 
>>> 
>>> 
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