Autocad Drawings for Practice Electrical

So, following TRLitsey's example, I attached a drawing index from one of our recent projects. It alone will highlight one of the problems we have with the word 'standards' here in North America. That being, that we don't really have one.

Now, that's *actually* not true - we do have the NFPA 79, of which the NEC (National Electric Code) is also a part. For all intents and purposes, these are our main 'standards' documents in the US for industrial design. However, there is no binding authority that says we have to abide by these standards. As such, their implementation tends to vary widely across America (and, I assume, the rest of the continent).

The most common reality for most of us is another thing TRLitsey said: just meet the needs of the client/customer. Often, industries have their own 'ways of doing things' that are unique to them. Railroads come to mind, everything they do just *has* to be different from what everyone else does. Sometimes, the nature of the industry makes things harder, for instance, aircraft design. Their schematics (along with most milspec schematics) can get pretty ridiculous... there tend to be lots of bulkhead connectors and such.

The company where I work builds equipment that supports the local bourbon industry, and we have our own guidelines to follow for working with flammable vapors/liquids in hazardous areas -- they're like an adjunct to NFPA 79, designed to address industry-specific concerns. So sometimes, your 'standards' depend on the industry.

As to your original post: In short, there is not a single place that will answer all of your questions. Really, books could be written addressing just these three issues. So briefly: How to design a schematic project? What's the order of operations? How not to clutter the drawings?

Not cluttering drawings sounds easy, but isn't always. The purpose of a drawing is to convey information, both graphical and textual. Drawings are working documents, and the information they contain is all-important. My goal is to always leave a healthy amount of white space on every drawing, for two reasons. First, to make it easier to read. It's so much easier to find a certain word or phrase when everything is nicely spaced out. Second, because I've been both a creator of drawings and a user of them -- meaning I've had to use someone else's drawings to build something. And for that person, the builder, the end-user, there is almost nothing about a drawing that is more important than having room to keep notes on it. White space is your friend (and theirs). When in doubt, leave it out.

To some extent, the symbols themselves will decide how much you can cram into a single drawing. Their size relative to the printed sheet matters, along with how much text there is. Best thing to do is try a few test plots to see what it's like to read your drawings. If they're annoying to use, if you have to squint to make things out, if you have to stare at it for a long time before it makes sense...there's too much stuff there. Open it up, paper is cheap, make more sheets. ACADE's tools make it easy to manage big projects.

As for order of operations...with ACADE, it can be pretty fluid. You can lay out the panels first, or draw the schematics. The software will support either workflow, and I've had to do it both ways. My preference is to do the schematics first though.

Before any drawings are begun, we have to understand the machine and its motion. We have to know how the machine designer intends the operator to run the machine. Sometimes, our input is needed for that aspect. Not until we have solid info on all of the electrical aspects of the machine do we begin drawing. Some of the things we like to know: motor sizes and anticipated loading; pneumatic cylinders and their function; all safety devices; all gates/doors/points of entry (because they will need to have safety devices); any pneumatic devices that need electrical power; field devices (often powered from/by the control system); customer's communication needs, etc. From there, we will specify how we want to control it (which PLC to use), how we want to divvy it all up among some enclosures, how to handle remote I/O, and so on.

When we're finally ready to begin the project: I will usually start with my highest voltage (usually 480V AC), place components in order of descending amperage, and then end with the transformer and/or power supply that gives me control voltage(s). Keeping the descending-amperage thing isn't necessary, and isn't always practical, it's just how my mind likes to see things laid out. But, many of the schematics from other places that I've worked with do it about the same way.

After the high voltage components (motors, VFDs etc), we move on to 24V DC, which runs most everything else. Here, the schematics are separated into power distribution and I/O. I/O schematics are further divided by rack and slot assignments, while the 24V power distribution is further divided by enclosure. (For example, let's say I have 2 remote control panels and a big operator station panel. I will give each one a whole drawing just to show its 24V circuits.)

Once all of the I/O is done, I then go back to the beginning and start thinking about where I need terminal blocks. I've been on ACADE for nearly 3 years, across 2 versions, and I'm still trying to find my best workflow for using the Terminal Strip Editor. We run everything to terminal here, and sometimes our terminal strips can be a little difficult to put together.

At this point I start laying out the enclosures and operator stations. Panel layout drawings are a totally different animal and I won't address them here since you specifically asked about schematics. But in theory every schematic is going to get built, so you'll eventually have to deal with panel layouts.

Which is the point to all this, really: Sometime, eventually, someone is going to have to use your drawings. For that person, the drawings are like a tool, a point of reference, a set of instructions, all rolled up into one thing. And that person matters more than you, or what you might think is important. That person will realize the real-world iteration of your design, and how well they execute that design will be a direct reflection of how much thought you put to your drawings, and what information you chose to include, and how well you organized it all.

If it's possible, I'd recommend that you get your hands on a schematic for a device or system that you're familiar with, or one that your company builds. We just hired a freshly-graduated electrical engineer, who has no practical experience in building panels, drawing schematics, or anything really. But he could READ schematics, and he knew a little bit about I/O and how PLCs worked. So I gave him a set of drawings for one of our machines that was about to ship out and let him crawl all over it for a couple of days. He'd never seen that machine before, but when he was done he mostly understood how it worked -- using no more than some schematics and some education and common sense. Could he design it? Control it? Of course not. The idea was to make connections in his head. So, the same thing might help you too.

Hope someone appreciates this novel I wrote,

Jim

Jim Seefeldt
Electrical Engineering Technician

perrycestion.blogspot.com

Source: https://forums.autodesk.com/t5/autocad-electrical-forum/schematic-design-and-good-practice/td-p/7611928

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