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Discussion: Rules For Drawing Readable Schematics

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Have any of you worked with Hierarchical Blocks ? I often see them being used in large complex designs with many pages. I would think they might be good for a block diagram type view, but for someone needing to debug a board or boards, following a hierarchical design might make it difficult. I have never used this method but curious as to what others may have done in this area. How do you push deeper into a block to see the components, especially in a paper version.

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.
 
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Another point that I don't think he made, in schematics wires should ALWAYS go either left, right, up, or down. When people draw schematics with wires going off at angles it makes it very sloppy and difficult to follow. The only exception I can think of is in a bridge rectifier schematic, but even then I would prefer that it be redrawn to be either vertical or horizontal.

Another exception (for angled lines) might be a multivibrator, where angled connections make sense. Otherwise, just horizontal or vertical, please.
 
Another exception (for angled lines) might be a multivibrator, where angled connections make sense. Otherwise, just horizontal or vertical, please.
I suppose I could accept that, provided it is drawn in a neat, clean fashion. One other exception that just occurred to me would be a star ground. Angled wires actually do a good job of indicating star grounds, but I would want to keep the angled portions of the wires as short as possible to preserve neatness.
 
I saw something really nice (once) in manual schematics. Labeled wire ends would end in an arrow in all sorts of directions. So, everything at 90 deg except for these occasional tails. The adjacent side of a right triangle would be part of the line. 1/2 the hypotenuse with an arrow on it would form the "tail" with an arrow. If you laid a straight edge along a tail, it would mate with the correct part of the circuit maybe all the way across the page. Less clutter.
 
There is another valid angle exception - diagrams with "bus" sections.

They are commonly drawn with a short angled section at a branch, which indicates which way along the main bus you need to look for the other end of the signal(s) in the branch. A bus branch may have a double angle if connections are to both sides.

That's common in various complex equipment schematics as well as digital gear.
Example:
schematic.png
 
That's common in various complex equipment schematics as well as digital gear.
Example:

A pet hate of mine, which the Japanese seem to specialise in...
a whole hoard of connections which run in parallel from one side of a schematic to the other, with several changes in direction along the way.
As typified in this circuit fragment from an Icom R72 receiver.

Icom IC R72 circuit fragment.png

JimB
 
One point about buses - it's like an express bus pretty much from one point to another, connecting similar pins from one place to another, like a entire port of a micro to corresponding pins on a memory chip.

It's not a cross-town bus, picking up a single bit or power connection here, a single bit from another chip there, dropping off a bit to a chip here, several bits to a awitch there. Yoi can't draw a bus around the perimeter of a schematic and have every connection on the schematic hop on that bus. Doing so defeats the entire purpose of a schematic.
 
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I've been creating my own schematic symbols and building my schematics with Windows Paint.
I posted the symbols that I've created in the hopes that they will help someone else.

Also, take a look at Kicad. It's a free EDA package that does schematic capture and printed circuit board design.

https://kicad-pcb.org/


SchematicSymbols.jpg
 
I've been creating my own schematic symbols and building my schematics with Windows Paint.
I posted the symbols that I've created in the hopes that they will help someone else.

Also, take a look at Kicad. It's a free EDA package that does schematic capture and printed circuit board design.

https://kicad-pcb.org/


View attachment 115903

Hi,

Yes nice.
Not many people use tubes these days but good to have i guess.
 
Hi,

Yes nice.
Not many people use tubes these days but good to have i guess.

You'd be suprised. :)

Audiophiles swear by them. Guitarists would rather lug a tube amp around than a small solid state amp,
simply because they sound better. Also, there are a few guitar pedals that have a bottle in the input stage.

I used the tube templates to design guitar amps.
 
there's a huge difference between what an audiophile is looking for in an amplifier, and what a guitarist is looking for in an amplifier. except for a small minority of audiophiles, most prefer an amplifier with very little distortion, a flat frequency response, and low noise. a guitarist on the other hand is looking for a particular "sound", which may be somewhat distorted, have a frequency response that is far from flat, and maybe a little bit of noise.

i use Kicad, and have made a few sets of symbols, mostly for some NXP micros. i use the symbol generator [found here].

i also use LTSpice a lot.
 
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You'd be suprised. :)

Audiophiles swear by them. Guitarists would rather lug a tube amp around than a small solid state amp,
simply because they sound better. Also, there are a few guitar pedals that have a bottle in the input stage.

I used the tube templates to design guitar amps.

Hi,

Yes i forgot about them. I used to have one too, an Ampeg amp. Sells today for about 1,000 dollars USD.
 
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