Electronics > Beginners
Modern way to specify values on schematics
CatalinaWOW:
Atarodov hit the key point. Make the schematic usable. If that requires violating rules fine.
Make the paper schematic usable. While the designer and manufacturer may always have access to the electronic version, the field tech or the guy who bought your stuff on the used market 20 years after sale probably won't. And even for the original designer paper often proves useful. I have yet to see the operation that can afford more monitors than sheets of paper and it is often necessary to refer to more than one schematic at once, and not infrequent to need several.
I'm torn on the number format. For my generation the 4R5 format is foreign and requires mental gear shifting. But it is the format that will be printed on the part if anything is printed at all.
bsfeechannel:
The SI prefixes were invented to avoid decimal points and commas. So, in theory you should write: 470mΩ, instead of 0.47Ω, or 2200pF, instead of 2.2nF. In practice, decimal points are really replaced by the prefixes but not exactly as dictated by the SI. When the unit is obvious it is left out.
I prefer 0R47, 100, 1k, 2k2, etc. for resistors, 2p2, 330p, 4n7, 68n, 2µ2, 10µ, 3300µ for capacitors, and 150n, 2µ2, 330µ, 15m, 10H for inductors.
There are traditional scripts, like 0.01mmF or 10kpF for 10nF, that you can find in vintage schematics. But they are a thing of the past, I guess.
AndyC_772:
--- Quote from: dmills on March 03, 2019, 09:39:26 pm ---Good advice until you hit the 600+ ball FPGA sort of part, where a few sheets for the power, one for the DDR IO bank, one for the network, a couple for the serdes starts to make a lot of sense.
--- End quote ---
Absolutely right. Separate the power pins out into a separate symbol, and put them on a different page, but don't actually hide them completely.
For some reason, when creating symbols in OrCAD, the option to completely hide any pin designated as a power pin is actually selected by default |O
bson:
Once upon a time people made photocopies of schematics. Things like connection dots and periods in numbers risked being dropped by an unfortunate blank spot in the copy. By using notation like 2R2 consistently there was never a question of if that speck was a mangled period or just a bit of dirt.
We no longer do that; if I provide you with a schematic (it won't be on paper) and you worry about losing periods or connection dots in photocopies you're doing it wrong.
TL;DR: it's a workaround for a problem that no longer exists.
filssavi:
Not related to component values but worth noting nonetheless...
When doing the schematic alerts put the actual nominal voltage in the name of power rail nets so when a different guy will have to troubleshoot your multi board design won’t have to go spelunking around trying to understand what the actual f**king voltage VDD, VDDA, VCC,VCCEXT etc are.
Also I never have seen in the 5 years I’m in the field someone photocopying a schematic, so I would say that decimal points are fine (If your printer has trouble printing dots, it has done its job and it’s fine to replace it)
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