Component Libraries - Am I just unlucky? - Page 1
Forum section: electronics / general

author: jpb
author_rank: Super Contributor
timestamp: March 07, 2016, 07:26:03 pm
content: I have been dithering for ages with choosing a low cost CAD package to learn and use.I decided the only thing was to actually try them - Proteus, DipTrace, Eagle and KiCAD (I had been hoping for there to be a obviously better choice and just go with that one but they all seem to have their faults in the low cost versions at least and a mixture of happy and decidedly unhappy users.)So I decided to get demo versions (or full version in the case of KiCAD) and lay out the little power supply circuit I've been working on.The key components in my circuit are LT3081 and LT3091 regulators and a Ref102 voltage reference. These are pretty well known components that have been around a while.First I tried Proteus demo and none of these components were in the library. Then I tried Diptrace and it didn't have any of them either and then I tried to get a demo version of Eagle and was presented with a detailed form which I'd have to submit before I could even start to download a demo so I canned that and finally tonight I tried KiCad and it didn't have them either.Am I just unlucky or are the libraries very hit and miss? Does Eagle have these components, for those who use Eagle?It now seems to me that you can pay £100s for software which is not only limited by pin counts or area or no cut-outs in ground planes (as in Proteus) but you also have to draw out standard components!I am perhaps a little naive but I thought that provided I stuck to simple circuits with common parts I could do straight forward layouts in the sort or drag and drop way that the videos show.Yes, I know that these components are in standard packages and I probably can edit some existing library elements but it has not been a good start to my trial.

author: bandgap
author_rank: Contributor
timestamp: March 07, 2016, 08:09:15 pm
content: I would not even consider the "built-in" libraries with any package. I would actually use that as a good opportunity to evaluate how easy it is to create new schematic symbols and footprints in the packages you are evaluating. You will have to eventually create them regardless of which package you choose, so this is an important consideration.-Clayton

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 07, 2016, 08:34:38 pm
content: The good news. Several of these packages actually have large libraries. Particularly Eagle.The bad news. It can be hard to find your component in the library. The search functions are usually primitive. Worse the people who generated those components all have their own idea of what key characteristics or key words should be and how they should be spelled. Part family (78xx for example), part type (7805 for example), package type, package technology, manufacturer and so on.But it can't be repeated often enough. Even when you find your part in the library you need to check it carefully to make sure it is what it says it is, that it is what you want, that it is correct (symbol, footprint and connections between the symbol and footprint) and that it is compatible with the board maker you use. Sometimes it really is easier to make your own components, but I often find a good starting point and go from there.My own experience says something like 5% are useable as is, 50% require minor tweaks and another 20% are close enough to be easier than starting over. Depending on the type of components you use you might get wildly different numbers than this, but it is likely to end up with lower utilization levels of the existing parts.That also leads to my own experience. About 40% of time creating the library for a project. A little more than 10% drawing the schematic. The rest is layout and routing. That is almost a perfect inversion of my interests, but that is the way it is. Others, with different skillsets will get other results, but I suspect that library and routing are the big players for everyone.

author: jpb
author_rank: Super Contributor
timestamp: March 07, 2016, 08:41:17 pm
content: Thank you both for your responses.When you look at the videos on web sites they give the impression it is all about layout and routing and they barely seem to mention the mechanics of entering new components. I guess they want to give the impression that the library covers everything.In fact my first thought was I was just failing to find the parts so I e-mailed Proteus (or rather the Lab Centre) and they responded to say the parts aren't there.So it looks like I'll have to put it bit more work into evaluating the packages than I'd hoped!

author: pcbguy1927
author_rank: Contributor
timestamp: March 08, 2016, 05:51:26 pm
content: Try here for the Ref102http://webench.ti.com/cad/

author: dadler
author_rank: Unknown
timestamp: March 08, 2016, 09:56:53 pm
content: I use Eagle.I started with these libraries:-http://www.bobstarr.net/pages/downloads.html- element14 libraries (they offer a bunch for download)- SparkFun libraries- Adafruit libraries- Microbuilder librariesWhenever I use a part from one of those libraries, I first clone it into my own personal, say "maxim-user" library. This is because I often tweak packages, names, positions, pin direction flags, font sizes, etc. I also confirm that the pins match the datasheet, and are configured in the schematic view in a sensible configuration.This is because I want to maintain consistency across packages, layouts, etc. It sucks to go to the board view, and have 8 different SOIC silk screens. I want all packages of a type to look identical, with consistent font sizing.I often make my own packages/devices from scratch. However, packages for most parts are standard, and all you have to do is draw a schematic symbol, and then assign the pins using an existing package.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 08, 2016, 10:05:45 pm
content: I am on Eagle, but have used others. I could not imagine using the libraries for anything other than a starting point. Even when I find a part in the library, it is most often in some state of wrong. After 'fixing' many library parts I soon learned that it was faster for me to created them from scratch most of the time. After I have verified all the details, I put the part in my personal library of parts that have been verified by me and safe to use.I eventually got into the habit of printing out the PCB on a laser printer at 1:1 to verify I had not messed up. Libraries are necessary and evil. They takes lots of time. I nearly went to Altium recently, but did not have enough time to deal with the library verification and fixes. The sales guy tried to convince me it was easy, I did not believe it.

author: jpb
author_rank: Super Contributor
timestamp: March 09, 2016, 06:58:09 pm
content: Thank you for the responses. It is very useful to get an idea of real world usage. Not least because I had been weighting libraries quite highly in my assessment of potential packages whilst from what people are saying it is more important to have a good system of part creation and library management.So far, in my very brief look, I've not found the creation of new parts very intuitive. I think that this is because each new part requires 3 or more representations (schematic symbol, footprint and possibly a 3D representation and perhaps an electrical SPICE model) but the CAD packages seem to be split into schematic capture, layout, simulation, 3D in separate parts so it seems you need to add new objects in bits.To my mind it would make sense to have a separate library component package. Instead (going by Proteus) you have to choose say schematic capture and then enter the schematic of the new element and I guess you then have to somehow link this to a footprint produced under layout. I may have this all wrong because I've not actually had time to do it properly yet.

author: nctnico
author_rank: Super Contributor
timestamp: March 10, 2016, 03:38:00 pm
content: IMHO a good package has the ability to have the components in (some kind of) a database. From this database which also contains information like part number, manufacturer, price, order codes, etc the right symbol and PCB footprint are linked together. I have been using Orcad Capture CIS (CIS=component database) for over 15 years now and I really don't want to go back to messing with seperate symbols and footprints and the errors manual work introduces. So yes, a good component management system is very important when choosing a CAD package.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 10, 2016, 07:05:59 pm
content: Quote from: jpb on March 09, 2016, 06:58:09 pmYou may not need all of the pieces of the model now, and may not ever use some of them. What is important is that you have a system for keeping track of the things you use, and that whatever you do it supports changes anywhere in the process. Design never achieves the ideal of a sequential path from concept to schematic to part selection to layout to manufacture. Different packages have different ways of keeping track of it all. What matches your personal style best may differ from others.

author: jpb
author_rank: Super Contributor
timestamp: March 10, 2016, 09:46:42 pm
content: Quote from: CatalinaWOW on March 10, 2016, 07:05:59 pmI agree. I think a schematic symbol and the 2D layout/footprint are fundamental - I can't see anyone not needing both - while the 3D representation and SPICE model and other things (EM or thermal models?) are things that are only really applicable to some users and probably can be shared between multiple components.And, as you say, the software should keep track of consistency.

author: nctnico
author_rank: Super Contributor
timestamp: March 11, 2016, 12:07:38 am
content: Quote from: jpb on March 10, 2016, 09:46:42 pmSymbols and PCB footprints are also shared. Think about a 22 Ohm and a 1k Ohm resistor. 2 different components with a shared symbol and PCB footprint. Copying the same symbol for different components is nuts and for more complex components it is necessary to change the symbol due to a mistake which is discovered later on. You don't want to change (essentially) the same symbol one hundred times. Unfortunately this is being overlooked by many of the lower end CAD packages.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 11, 2016, 03:16:22 am
content: Quote from: nctnico on March 11, 2016, 12:07:38 amThe thing that may have been missed about my comment is the need to have changes downstream in the process reflect back up into the documentation for earlier stages. And the desirability of easily linking other parts of the model in as a need is developed.Also it is easily overlooked that even for a resistor there may be dozens of footprints. Which footprint is used for a given part may change based on discovery in prototyping, part availability, changes in vendor selection and many other factors. That problem compounds as you go to more complex parts. Factors like Pb free impact footprints, manufacturing requirements and part availability and need to be documented at appropriate points in the design flow.There are many ways of skinning this cat. Just recognize that it is a very big, complex cat and you need a plan to deal with it. There are people in these forums who have very strong opinions on the best workflow and methods to solve the problems. Many of them are very experienced and their opinions should not be ignored. Even though they do not all agree. And even if their answers are not right for your situation. You should understand what they are saying and have a good reason why your situation either demands or can accept a different answer.