Schematic capture? with PCB fabrication in mind? - Page 1
Forum section: electronics / beginners

author: TriodeTiger
author_rank: Regular Contributor
timestamp: October 13, 2012, 04:20:04 am
content: I sometimes struggle with certain steps, and cannot seem to find any way to answer them.I wanted to create a simple R2/R ladder DAC with microcontroller on a PCB, just as an example.I opened up an instance of DIPTRACE and was faced with various Crystals to place. Alright, some are there, but none were the frequencies I wanted (nor did I really want to search each model's name for availability or specifications on digikey) so I chose one myself.On Digikey, I hit ... MHz crystal, through-hole, in stock, 16MHz for the purpose of my attempt and found one.http://www.digikey.ca/product-detail/en/ATS16B/CTX1085-ND/2640031Alright, Its manufacturer name is ATS16B which isn't in there, but if it was I pretend not, and am satisfied. I find out it is in an HC49/US package from the specifications - and then all goes blank.I can find a similar package in DIPTRACE that has an HC49/U, two leads. Scrolling down I find one with an HC49/US footprint and for some reason it has three leads - or at least three circles indicating such from first look. It confuses me if that is even the right footprint.Should I ignore all of the defaults and assume they are for some other general purpose, and create my own crystal each time? Is there some sort of quick generator to say ... "HC49/US footprint, desig=X1, name=16MHz" and have a footprint I can now use?I remember Eagle you can create libraries, however that took so many steps I started to regret having to do this. I seem to recall Altium having some sort of component generation wizard, but do not use it.I have no trouble making a schematic work, but translating it in to PCB with proper footprints and names and all of this from parts I find (say generic op-amp in a standard DIP-8 package) I do not know whether I should create a new part, use a same sized DIP-8 and rename it (I really dislike doing this, it feels dirty) or there is some sort of step.Alexander.

author: Kremmen
author_rank: Super Contributor
timestamp: October 13, 2012, 06:26:32 pm
content: One thing you need to realize and accept is that there are far too many components out there for you to ever find all of them in a standard library of a scematic capture/PCB layout program.I use Diptrace for all my hobby projects and i find myself creating almost every component i use. One big reason is that i insist on using strict IEC style symbols only, and those are not too commonly available in Diptrace std libraries. Another issue is that i also use metric dimensioning only - all components must align to a 1 mm grid. This is not Diptrace default.For run of the mill jellybean components, the Diptrace standard footprints work nicely. For everything else i create my own. Note that you don't need a dedicated footprint for every component, and also the symbols can be reused for many harmonized components such as passives, some opamps and standard logic. I often combine an existing schematic symbol from one library with a footprint from another. Bear in mind that Diptrace stores both in the schematic file so every drawing is effectively its own "library".Still, i would prefer a total overhaul in Diptrace component database - or let's rather say that it would be good if there actually was one. Now locating a component is almost hopeless unless you have a pretty good idea what exactly you are looking for.Learn to use the component and footprint editors well and many of these problems go away. It is actually rather easy to create components on the fly. This is anyway something you need to do - so many components nowadays have some kind of proprietary or special footprint...