What is the relationship between the .lib files?

[AndreKR]

I’m new to KiCad. In my project folder there are two .lib files, <project name>.lib and <project name>-cache.lib, whose purpose I’m trying to understand.

If I assume that <project name>-cache.lib is just a cache for technical reasons then my question is mostly about the <project name>.lib. What I found out so far:

• I cannot edit <project name>.lib from the KiCad main window (“Library not found in symbol library table”), presumable because I don’t have (and don’t need) a sym-lib-table in the project.
• It seems I cannot edit symbols from this file with Ctrl+E nor Properties > Edit with Library Editor, it will instead edit the symbol in the global library.

I’m using KiCad 5.1.10.

So is this file for when I copy the project to another machine that doesn’t have the global libraries? What if it does have the global libraries but they contain conflicting information? And what about the cache file, should I manually exclude it when I copy the project to another machine?

[paulvdh]

For the cache file:

What are the cache and rescue libs and how does the schematic rescue dialog work? (KiCad version 5.x and earlier)

The purpose of the cache library KiCad version 5 and earlier do not include symbol information in the schematic file format. Without any counter measure changes to the libs would change the schematic without user control (worst case a symbol is deleted from the lib and the project looses its information). This is where the cache lib comes in. Anytime a user adds a symbol to the project it is copied to the cache lib for save keeping (unless the same symbol is already in the cache). If now the li…

Apparently you have made a new library in your project.

@AndreKR

I don’t have (and don’t need) a sym-lib-table in the project.

Euhm, no.
If you want to use that library in your project, you have to add the library to your project, and KiCad saves that setting in the sym-lib-table file. Result is that if you delete the sym-lib-table file from your project, then KiCad does not see the project specific libraries anymore.

Library management in KiCad version 5

Disclaimer: screenshots taken in nightly from between version 5.0 and 5.1. Version 5.0.x looks slightly different. Version 5.1.x will look like the screenshots show. This is a detailed lecture. If you want to know how to simply add some assets you downloaded to KiCad then you can read the shorter tutorial How to get a downloaded symbol, footprint or full library into KiCad version 5? Summary KiCad does not automatically detect libraries! There is no special library location (you might still ca…

[AndreKR]

@paulvdh

Apparently you have made a new library in your project.

Hm, interesting. Certainly not on purpose. It has all the symbols in it that I have used in my project. If KiCad has a function to create such a library, I might have triggered it inadvertently. I just played around with a fresh project and indeed the <project name>.lib file normally is not automatically created.

[paulvdh]

@AndreKR

It has all the symbols in it that I have used in my project.

This is normal for the “[Project]-cache.lib” file.
Maybe you once renamed that file by removing the “-cache” part?
Maybe the file date gives a clue to (when, and thus: ) why you created that file. But it’s probably not all that important. For people new to KiCad (or any other PC program) it’s common to click on buttons and try things out just to see what happens. And it’s also common to not understand it all and forget what you did (Especially if you did not understand what the results of an action were)

[AndreKR]

I’m pretty sure I didn’t manually rename it, but if there’s a menu item for that, it’s entirely possible that I did that.

Anyway, now it’s gone. I deleted it using the KiCad GUI and apparently that really permanently deletes it, even bypassing the Recycling Bin. So I can’t check the file date anymore. Luckily it seems to have no ill effect on my schematic.

[jmk]

He, he,
Make a change in your project, and save, and your cache library will be back