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Discussion: Rules For Drawing Readable Schematics

Discussion in 'General Electronics Chat' started by atferrari, Jun 10, 2015.

  1. spec

    spec Well-Known Member Most Helpful Member

    Oct 27, 2015
    Somerset UK GMT
    If I read you correctly, yes.

    We used them extensively in Protel/Altium where they were a godsend, especially on a complex system with a lot of functional units. In most cases the hierarchy was:

    Overal system (block)→ sub-system (block)→ rack (block)→ frame (block)→ card/psu/modules, etc (circuit diagram).

    At project kick-off, it takes some time and effort to get the overall system block diagram right, especially ensuring that the interconnection names are consistently labelled, but it pays dividends in the end.

    The whole design, including board layouts, manufacturing data and so on, was hosted on a central computer with access rights granted according to your project function. You could view everything though. Of course, strict configuration control was essential. Each drawing had a unique number which reflected it place in the structure, along with issue and date.

    In terms of paper output, that was excellent; all the project documents were filed in A3 folders which were kept in cabinets in a small room. The document structure reflected the design structure. And you could export to PDF etc. Most of the fundamental design data, system block diagrams, circuit diagrams, was on A3 sheets from a massive plotter at first, but later a laserjet.

    Each engineer, regardless of his department, was responsible to the Project System Engineer who had overall access rights, rather like system admin on ETO.

    The other advantage is that the user documentation (handbooks, maintenance manuals, etc) was much easier; more or less cut and paste for many illustrations. It also helped the project management with their PERT charts, progress meetings and all that stuff.

    Once the first project had been done, the next project would use much of the same design documentation so the start-up period was much less.

    Each designer had to make sure that any modifications he made to his area didn't impact the system. If they did he had to clear it with the Project System Engineer who would update the higher level design as necessary.

    The above may sound like a sales pitch, but when this system was first proposed, I for one, was dead against it, fearing that it would end up as a bureaucratic nightmare and hamper progress, which is always the danger with these systems. Luckily, it was in a research department, and the managers were proactive. In life there are always problems: the CAD system would hang, libraries always take an age and anyone not following the rules could create havoc. Also, the software, as always, was a bit flaky in places.

    I even used Protel for home projects, on a very minor scale, but at least I was Project System Engineer. Having retired though, I have lost my home licence so I'm currently learning Eagle, a slightly lesser ECAD it seems, but more than adequate for drawing schematics, and possibly doing PCB layouts.

    After all that, the answer to your question is that you can show as much detail as you like at the block level, with Altium, anyway. I haven't got that far with Eagle. With a few printouts in front of you, you can easily channel down or up from one level to another which is a great help in following the design and debugging. Of course, the components that you mention are normally shown at the lowest level.

    I hope I have understood your question correctly and have not been going on about something you are already familiar with.
    Last edited: Nov 14, 2015

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