Pin Numbers or Pin Names?
I make the following symbols in my schematic editor:
When I import my netlist into VeeCAD, I want to see components like this:
Unfortunately, I have to make 3 different library outlines in VeeCAD, because
the 3 components have different Pin Text. I fix this by giving all pins the
same text like this:
So, if you want to make outline libraries without duplicating many outlines:
number pins, don't give them electrical names like +/-, A/K, Anode/Cathode,
CBE, SGD, AKG, IN/OUT.
Here is another example: two parts which use the same DIP-8 outline provided
numbers are used instead of electrical names:
Organise Your CAD Libraries
These principles apply whether you are using a PCB layout program or VeeCAD for
- Use only pin numbers
- Enter each outline (footprint) once only in your PCB or VeeCAD library
- Use shape names like SOT-23, DIP-8, Axial_2_7, Radial_12_02 for outlines,
not electrical terms like Diode_01.
- Use cathode = 1, anode = 2 for diodes
- Use + = 1, - = 2 for polarised capacitors
- Don't use generic transistor or SCR symbols then set footprint name and
type attributes on the fly in the schematic editor. This requires checking the
datasheet every time you place that part, wastings time and causing errors.
- Take the time to draw a separate schematic library symbol for each transistor
diode, IC etc. part number, with footprint name and pin numbers correctly set.
Now you have a trusted component you can place in any schematic, knowing it will
safely get through to your layout.
Confusion in the CAD World
If you work on PCB CAD projects, you may have noticed these problems:
- Multiple outlines (footprints) which differ only because of different pin names
- Identical parts using different outlines
- Variants of the same outline drawn by different people
In modifying such projects, one must guess at the correct outline to use,
duplicate an existing outline and rename the pins, enter an additional outline
created from a datasheet footprint, modify a schematic symbol so as to use an
existing footprint, etc. This work is costly and produces board and manufacture
problems. Worst of all, a company cannot build up a standard parts library of
preferred parts. So use the library system explained here!
Special Case: Matching Your PCB CAD Footprint Names
If you want to build a VeeCAD library which is compatible with your
schematic-PCB package, you will have to abandon the Pin Numbers Only rule and
match your schematic symbol pin names. This will mean duplicating some VeeCAD
outlines and altering the pin names.