Schematics technique

For simplicity, let's keep this hypothetical :

You are diagramming the interconnections between two machines. Machine A sends three +24 VDC signals to Machine B, via interposing relays. Machine B returns the favor.

Where the relays are located physically is irrelevant to my question - I'm not trying to rehash the "wet-dry contact" issue What I want to know is, how do you like to see this sort of relationship drawn on a schematic?

For instance, would you work it into the regular IO circiut diagrams somehow, or dedicate a page specifically to this relationship? If the latter, what do you do with the IO on the normal page? Ignore it? Use a line jump to the page? (Hmm, may have just answered myself...)

I'm really curious to see your individual approaches.

Thanks!

TM

Clarification

This is what I mean about "including it in regular IO". In this instance, I'm communicating with a servo, and just call out the terminal involved.

If the devices are all used in the same schematic (relay isolation between a plc and a drive in the same cabinet, for example) I usually show the relay coils on the sheet where they are driven and the contacts on the sheet where they are used. I then use cross-reference numbers between them. The upside is it shows the information where it is actually relevant and doesn't split a single device across multiple pages (except for the relay, of course).
The downside is that someone looking at the drawing can't get the big picture on a single page. Also, drawing modifications may change the cross-reference locations so you have to babysit them too.

With machine-to-machine interface where I don't have control of either the use or source of the signal I do something similar except without the cross-reference. With signals from somewhere else I show the contact in the normal logic with a note that it says 'from customer' or something like that. For signals from me I show the coil where it would normally be driven. I then cross-reference to a separate page that shows the interface signals as contact closures with functional descriptions and the general note 'To Customer'. If I get the signal and source information after install I will update the drawing with the additional information.

Hope that's what you were asking about. It will be interesting to see other people's methods since I'm not sure I'm 100% happy with what I just described.

Keith

Yep, that's the stuff!

That's exactly the sort of information I'm looking for, even better since it wasn't either of the ideas I tossed out as examples.

Thanks for the answer, and I too am anxious to see what sort of responses we get.

TM

most guys do it the way you do. I prefer to show the outputs as if they were contacts, and the inputs as if they were pilot lights. That lets me se at a glance the ineterlocking with other equipment or external circuits. I cross referenece the I/O to my point list.

Tim I will see if I can copy some drawings as examples tomorrow. I have some European machines, German and Italian, the older machine schematics seem to have a method that took a learning curve to follow. The newer German and Italian machines follow the same method (maybe its an IEC guideline, I havent determined this as fact yet).

Either will use block reference with the contact device from the other machine OR a termination point and wire number with reference to machine/wire number/schemtic page. I will see if I cant scan some to show this in better detail. Since these machines have multiple page schematics the page/machine/wire number reference makes it a little easier to track down problems.

Tim,

I just use an asterisk that refers to another drawing

see below in purple

[attachment]

Ian,

This is the other sort of example I was describing. You refer the reader to a separate drawing, with all of the wiring connections for the device shown on that page.

Ron,

So the euro's use both? Now I wonder what criteria makes them decide on one or the other! Ahh, shoot, now I have stress... But I'm looking forward to the examples.

Lastly, what brought all of this on is, I'm re-writing a few schematics, and I'm not satisfied with the quality and with the time it takes to generate them.

I'm trying to identify: 1) What is the best approach to show relationships between controllers and peripheral equipment (as opposed to a simple solenoid or lamp? 2) What is the best approach for documenting interposing relays, specifically, same page or separate page? 3) What in a schematic can be omitted for clarity's sake without sacrificing tracability?

Probably should have said that in the first place, huh?

TM