schematic etiquette - Page 1
Forum section: electronics / general

author: subolg123
author_rank: Contributor
timestamp: April 11, 2014, 05:40:02 pm
content: it might be time to craft a short video on schematic etiquette.

author: miguelvp
author_rank: Super Contributor
timestamp: May 02, 2014, 01:29:49 am
content: By all means, power rails deserve their own page, don't mix them with other stuff just because you have the space to do so.But I'm a noob.

author: free_electron
author_rank: Super Contributor
timestamp: May 02, 2014, 01:35:40 am
content: hmm. interesting idea.. i'll add a chapter to my next book on this. (book on PCB design)

author: SL4P
author_rank: Super Contributor
timestamp: May 02, 2014, 07:47:15 am
content: My vote - where possible ----- Signal flow from left-to-right- and also when it doesn't confuse the purpose of the drawing - inputs of parts on left / outputs on right- mixed i/o to go where it best indicates the function of the circuit--Supply railsin descending voltage from top-to-bottom - where it makes the diagram more readable.--Connectors & Ports- when possible, Inputs arriving from the left / Outbound pointing to the right... !- preferably in a similar layout/order if they arrive on another sheet that makes them easier to mentally associate.- same for connectors that appear on different or separate sheets.Schematics are documentation to be read in the future- not just a means to generate a netlist and PCB layout !

author: ignator
author_rank: Regular Contributor
timestamp: May 02, 2014, 05:55:13 pm
content: Make all the rules you want. Only you can follow your rules.PC drafting don't follow your rules. They can't read schematics, and they never worked on any electronic anything first hand.All they want is a netlist, PWB artwork, BOM and auto insert data base. They don't maintain the product.This is what I learned in 30 years of working on avionics.It was frustrating, PC drafting fell into "engineering services" organization. They had their own vice-president. And a fundamental rule of large organizations is never say anything bad outside of your organization. So in the 30 years I was there, it never improved. The design quality was left to the engineer, and how tenacious they were in dealing with idiots.You could leave a list of layout rules, and they were ignored. There were a few designers that knew what they were doing, but you could never get them to work on your board, as they were in demand and everything was a que to get through their hurtle. The organization did everything to prevent engineering having access to the schematic capture tool (EPD), and the board layout tool (VISULA/CR5000).To try to add to useful input:Notes for service center technicians that (especially for analog) indicate the signal processing blocks. If you stick build a differential amp, draw it so it looks like a differential amp.For processor based sch. have a memory map on the processor or memory page.Layout notes that are released with the schematic are good (for future support by the next cognizant), if they can be excluded from the published version to limit intellectual property info.

author: miguelvp
author_rank: Super Contributor
timestamp: May 03, 2014, 01:33:19 am
content: I believe this is meant as in sharing schematics for peer review or as in open source hardware, not as in submitting them to your manufacturing house.

author: zapta
author_rank: Super Contributor
timestamp: May 03, 2014, 04:11:19 am
content: How would you critic the schematic in page 3 herehttp://www.mikrocontroller.net/attachment/193474/MX-500P-11.pdf?My own are much more decoupled but I appreciate the compactness, planarity and the artistic aspects of that one.

author: miguelvp
author_rank: Super Contributor
timestamp: May 03, 2014, 04:38:56 am
content: Quote from: zapta on May 03, 2014, 04:11:19 amTest point voltages would help, way too compact and reminds me of 60's circuits on the back of consumer audio equipment manuals.

author: pickle9000
author_rank: Super Contributor
timestamp: May 03, 2014, 05:09:52 am
content: I always encouraged the "Think of the next guy" rule.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 03, 2014, 05:31:44 am
content: Although this page is about the use of my bitmap symbols, the rules in general apply to most anything:http://webpages.charter.net/dawill/tmoranwms/Elec_Circuit_Rules.htmlSome day I would love to make the symbols in 300 DPI bitmaps, and vector format. And have either a schematic capture program, or a netlist with hints, or something, to use them with. A lot of work either way, and especially for the latter, I don't know nearly enough about LaTeX programming to be able to do it. The result would be excellent though.Tim

author: Neilm
author_rank: Super Contributor
timestamp: May 03, 2014, 06:39:37 pm
content: I have worked at a company where we used a database for the symbols. The only problem, this database was administered by mechanical engineers (who also do our board layouts). Result, the symbols could have the pins anywhere - usually the electronic symbol was just the chip package. A square block with pins on it - output usually being on the left.

author: Kremmen
author_rank: Super Contributor
timestamp: May 03, 2014, 07:19:56 pm
content: Mostly good suggestions so far. One thing that i would like to add in this day of the all pervading digital microchips: please, do use logic symbols that are more descriptive than the dumb blank rectangle with unidentifiable pins scattered around the perimeter. IEC (for one) has done a good job in coming up with a vast library of descriptive graphics elements to help visualize the functionality and features of specific logic and other circuits. Granted, there is a learning curve and some effort is required in correctly applying those but the reward in elucidating the functionality is considerable.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 04, 2014, 06:41:47 am
content: EWwwwwhewwhewww (shuddering), IEC symbols.So ugly and undescriptive. How very European.Tim

author: German_EE
author_rank: Super Contributor
timestamp: June 12, 2014, 03:39:57 pm
content: So, a question about drawing a schematic. If you have to draw a 16-pin IC do you draw the pins in numerical order or are they grouped by function with inputs on the left and outputs on the right?

author: KJDS
author_rank: Super Contributor
timestamp: June 12, 2014, 04:12:28 pm
content: Quote from: German_EE on June 12, 2014, 03:39:57 pmThe schematic symbol should be a schematic, so inputs on left, outputs on right, power supplies on top and grounds on the bottom. CLumps of pins should be tgrouped together, so address pins 1-16 should be in order on the left hand side. Data pins 1-16 should also be in order, and as they are input and output then put them on the side which looks neatest for the part.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 12, 2014, 05:10:14 pm
content: Quote from: German_EE on June 12, 2014, 03:39:57 pmThe people who draw IC packages per the physical layout seem to be mostly those with no understanding of electronics. For example guitar players hacking together some stomp-box circuit, etc.No offense to musos. It is encouraging that they are exploring electronics. But dumbing-down the schematic diagram isn't helping them learn anything except which pin to solder the wire to.The word "schematic" implies that it shows the SCHEME of the circuit, NOT the physical layout. The physical layout is useful when you are trying to find components on a board, but the SCHEME is what you need when you are trying to understand/debug a circuit.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: June 13, 2014, 10:40:27 pm
content: I am an occidental, by which I mean my roots are European, American, etc. Our writing is left to right and top down.For me it is easier to see schematics laid out in the way. Indeed there have been a number of comments about 'poorly' drawn schematics that do not follow this system.Other peoples have writings which work differently, Chinese, Arabic etc.Just as matter of interest and ignoring international peer pressure how do the non-occidental (for want of a better description) members of this forum feel what a 'natural' schematic layout should be?

author: Zad
author_rank: Super Contributor
timestamp: June 14, 2014, 02:36:01 am
content: Quote from: subolg123 on June 12, 2014, 05:02:41 pmFunnily enough, this illustrates one of my pet hates - having a small number (sometimes even one) of components on a sheet, with lots and lots of words and "mess".All we have here is an automatically generated list with some graphical augmentation. Diagrams should give you some idea of the logical operation of a system. Adding extra clutter to the components, with attributes such as tolerance, power, composition (metal film, COG, ceramic etc) and physical dimensions just obscures the circuit diagram and removes from its usability.A diagram is an abstraction, losing detail which is unnecessary. Most of the time, all that is needed is component number and value. All the attributes and so on can be stored on component detail pages. I don't know if this is genuine Apple, but it smells of Chinese reverse engineering.