Schematic with 2 dots drawn, instead of perpendicular crossing and a single dot  - Page 1
Forum section: electronics / beginners

author: RoGeorge
author_rank: Super Contributor
timestamp: October 18, 2023, 08:38:05 am
content: I've seen similar drawing in schematics a few times (very, very rarely), and now seen it on the cover of a book (the drawing marked with "X".Why tilting 45 degree then drawing 2 connection dots, instead of perpendicular crossing and just one dot? What is that symbol for?

author: Ranayna
author_rank: Super Contributor
timestamp: October 18, 2023, 08:43:50 am
content: I remember that there is an old-ish convention to not draw a crossing with a dot, because after a couple of copies the dot might be lost, and you can't be sure anymore if the lines should be connected or not.Instead, you should shift one of the lines to create two "t-junctions". These are connected, while a crossing is not.I have never seen the variation that is used on your cover, and i have no idea what the X might mean.

author: magic
author_rank: Super Contributor
timestamp: October 18, 2023, 08:49:30 am
content: It's the symbol of avoiding 4-way junctions, which some people believe are too easily confused with crossing wires.And they are right to an extent, as there is no shortage of screwed up schematics with missing or wrong dots here and there. Even without photocopying.I usually avoid such junctions too.If you want to see something truly evil and tiresome, try 20th century Texas Instruments IC datasheets. They used to have a sick obsession with never drawing lines through the middle of multiple transistors, like all normal people do when the bases are connected together. This made for some interesting mazes...

author: RoGeorge
author_rank: Super Contributor
timestamp: October 18, 2023, 08:54:57 am
content: We used to draw a small semicircle when 2 lines were crossingwithoutelectrical contact, or a dot when they were crossingwithcontact.The newer convention, without semicircle and based on the absence of the dot, is indeed hard to read.Some other guidelines were to avoid lines crossing unnecessarily, and to avoid unnecessary angles (i.e. don't draw a corner like a staircase line).

author: soldar
author_rank: Super Contributor
timestamp: October 18, 2023, 09:20:07 am
content: Another way.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 18, 2023, 09:28:55 am
content: Bear in mind that probably dates back to when schematics were photocopied - a dot can easily get lost in the process.

author: wasedadoc
author_rank: Super Contributor
timestamp: October 18, 2023, 10:03:07 am
content: The X is not part of the schematic per se. It is probably marking a point which is referred to in the text.

author: soldar
author_rank: Super Contributor
timestamp: October 18, 2023, 10:22:12 am
content: Quote from: mikeselectricstuff on October 18, 2023, 09:28:55 amOr a dot could appear where two lines crossed and there should be no dot.

author: Ian.M
author_rank: Super Contributor
timestamp: October 18, 2023, 11:08:53 am
content: This can also happen with excessive JPEG compression, which is why rendered schematics should only be posted using image formats with loss free compression.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 18, 2023, 11:23:46 am
content: Inside the book the crossed contact wires are not like on the cover.The stile on the cover adds a little bloatware, but at least it's aesthetically pleasant. Inside the book they adopted the style with slightly misaligned wires connected in two places. IMO that style makes the schematics look like a mess.The book is from 2010, when desktop publishing SW was ubiquitous, so I don't know how they end up with drawings like the attached example (horrible style if you ask me, and sometimes wrong/sloppy - e.g. the dot to ground at C7, or those misleading bus-bars instead of using the GND symbol, even the ratio between length and width of the resistors looks wrong - they seem too long, transystors are flipped, +/-15V drawn to the signal input side, unnecessary corners in the node marked with 0V, etc. everything looks wrongly drawn and hard to read).

author: MrAl
author_rank: Super Contributor
timestamp: October 18, 2023, 11:44:59 am
content: Quote from: RoGeorge on October 18, 2023, 08:38:05 amHi,I come from a power systems background and unusual drawing techniques like that may come up in order to show the proximity of the connections to one another and/or to another connection point in a real circuit. That comes up because of typical grounding problems that can cause problems.For this circuit, that would mean that the top circuit part would be connected physically closer to the input resistor (left side) while the bottom circuit would be connected somewhere after the top circuit connection. The two connections could be many inches apart for example, or just even one inch.This happens with power circuits because there is often high currents flowing in the traces or wires, and that means extra voltage drops that you may not realize are there with a simpler schematic. Often the wires drawn on the schematic are shown using thicker lines also.For an example of this, you can look up some of the National Semiconductor Simple Switcher data sheets.It's doubtful if that's the case here though because the circuit contains mostly regular op amps, it's just something we might see elsewhere. For this schematic it may have been simply the use of artistic license in order to make a more interesting image without any real concern for any technical accuracy. We see this from time to time but usually it is more apparent that it is not a real schematic.

author: magic
author_rank: Super Contributor
timestamp: October 18, 2023, 12:05:20 pm
content: Quote from: RoGeorge on October 18, 2023, 11:23:46 amAre you sure?Look up "active clipping with opamps" in "level control and special circuits"

author: AndyBeez
author_rank: Frequent Contributor
timestamp: October 18, 2023, 12:06:42 pm
content: Maybe in that CAD, stepped links make the autorouting and rats nest easier - 4 wire nodes are not supported? Otherwise it is just a nice thing that old draughtsmen with pencils and paper used to do.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 18, 2023, 12:42:33 pm
content: Quote from: magic on October 18, 2023, 12:05:20 pmOK the schematic on the cover is from the book, indeed.Maybe the schematics are collected from different places, that would explain the drawing style inconsistencies along the book.But is the book worth reading? Asking you that because I've only arrived at that book today, after clicking one of your links in another EEVblog topic.

author: TimFox
author_rank: Super Contributor
timestamp: October 18, 2023, 01:14:01 pm
content: There is a lot of useful detail in that book about low-level audio design.-Comparisons on the op amps available up to that date.-Detailed description of RIAA equalization circuits.-A thorough discussion of mixer circuits (as in microphone mixers for recording or stage amplification).-Actual measurements of passive-component distortion, such as different capacitors.My personal preference, having started drawing schematics by hand 50 years ago and later transitioning to CAD, is toneverhave a "+" crossing be a connection, and to prefer a "hiccup" at a non-connected crossing.

author: soldar
author_rank: Super Contributor
timestamp: October 18, 2023, 02:49:56 pm
content: Quote from: TimFox on October 18, 2023, 01:14:01 pmI agree that the best way to avoid the ambiguity of a + is to not use it. Use a blob if connected and use a "bridge" ("hiccup") if not connected.

author: Zero999
author_rank: Super Contributor
timestamp: October 18, 2023, 07:50:08 pm
content: I've seen that before and occasionally done it myself.I also avoid using a single dot for four connections. For crossing wires I prefer to use a semicircle or broken line, but LTSpice doesn't do it and I'm too lazy to edit the screenshots.

author: EPAIII
author_rank: Super Contributor
timestamp: October 19, 2023, 03:17:11 am
content: Well, call me a dinosaur if you wish, but I ALWAYS use the dot for a connection and the half circle bridge for no connection. I never just cross two lines in a schematic. As multiple people have said, it can be confusing. This is actually the older convention, not what you show. I have observed that lazy draftsmen have been trying to change it for 40 or 50 years now.Two close perpendicular connections, each with it's own dot are perfectly OK.And the half circle bridge should always be on the horizontal line, not the vertical one. I even wrote a macro in my 2D CAD program to break a horizontal line and insert the half circle bridge.I would never think of using the 45 degree arrangement in the photo, but I see nothing in it other than a peculiar way of showing those connections. It is perfectly understandable.As for the single, continued line for the base of multiple transistors, when I saw it for the first time I understood it in less than a micro second. No problems there. Does anyone really misunderstand it? I can't imagine how.To my ancient mind, these are just the way things should be done. There is less chance for error. That's my opinion and I am sticking to it. And Pluto is big and it circles the sun so it IS a planet. So what if it hasn't cleaned house yet: I'm not so good at that either so I can forgive that fault. And units of measure named after real people should be capitalized: Ohm, not ohm, Volt, not volt, etc. Otherwise you are insulting them instead of honoring them. Methinks that those who are making these decisions are just jealous of the real great minds among their ranks. You can't fool me no matter how much alphabet soup you have behind your name. So there!OK, rant mode/OFF.Quote from: RoGeorge on October 18, 2023, 08:54:57 am

author: RoGeorge
author_rank: Super Contributor
timestamp: October 19, 2023, 06:16:44 am
content: Same here, when I draw by hand I only use the upper-right (semicircle) and lower-left (the dot) symbols.