Alias and long MPNs in symbol libraries


#1

Hi, I wish to use the WSHP2818R0500FEA current sense resistor from Vishay in a design. I created a new symbol in my libraries using the R_Shunt base symbol, and simply named it WSHP2818R0500FEA.

However when I use the part in a schematic, I find that the MPN is too long in the sheet and irrelevant for quick electrical analysis. I would rather like to see “50mΩ 1%” instead of the long MPN, but still see the full MPN in the library editor. So I modified my symbol in the library to hide the symbol name (WSHP2818R0500FEA), and added a new value field called “Key Parameters”, having the value “50mΩ 1%”. Now this would solve my problem. However when I wanted to create an alias for a similar resistor, I realized that my new value field was also copied, and could not be modified independently modified from the one of the original component. So it now appears that I won’t be able to use this approach with alias, and I am stuck with using long MPNs to differentiate alias. Does anyone also encountered this problem? A solution for this would be to have the liberty of using independent value fields for alias.


#2

Hm, most of us who do this for a while set up our personal libs to use descriptive part references and have the manufacturer ID in a separate field:

Some go even further and use an internal part number (house part number) instead and keep track of the BOM and parts acquisition by another department via some external scripts.


#3

House numbers are better as manufacturers part numbers are in constant flux


#4

I understand the logic of having the MPN in a separate field and simply using a descriptive name for the part in the “Value” field, but in this way aliases can’t be created as they would all have the same MPN. This approach thus can’t be used in conjunction with aliases. In other words, this renders the alias functionality useless.

Right now no other value field besides “Value” (i.e. the name of the part) is allowed to change for an alias of a part. This is problematic. The only workaround I see would be to stop using aliases and creating each part on its own as I initially described.


#5

Alias:

Which is exactly what the alias is supposed to do, give you another avenue to access the very same part with the very same man ID or house part number - just under another moniker.

?!?

parts in KiCAD are identified by their Reference once they are in the schematic.
That’s it.
All other fields, be it value or whatever you come up with are not supposed to be unique.

That the symbol library handles the parts at first by it’s value right now is a little restricting and cumbersome, as most often a simple value is not enough to ID a part sufficiently and on the other hand the value field with all that information later on is definitely overloaded, but as long as this doesn’t change we have to live with that.
And it was/is even worse… as if you had a 100nF for different cpacitor families/types and your value field only had 100nF in there… well, let’s just say this is not geared yet for real parts libraries, but for the need to use CvPCB. KiCAD is still evolving and getting better in this regard, adding new features, while keeping the hoobyist(?) way of doing things as a valid approach to design pcbs.

PS: I hope it’s understood, that as soon as a part like I showed you above lands in my schematic I edit the value field and restrict it to the important stuff only. Still easier than to edit each and every additional field and assign footprints.

PPS: have a read here, gives you some insight to what will be happening in that space:


#6

I personally prefer not having to modify the fields of any part from my libraries once I drop them in a schematic. For now I will work around this issue.