Schematic Drawing - Best Practice - Page 1
Forum section: electronics / projects

author: Vonsgarage
author_rank: Contributor
timestamp: March 11, 2024, 10:11:11 pm
content: Good day.I am in the middle of tracing and redrawing schematics for a old reel to reel tape deck.In your expert opinion do you like the idea ofbreaking the wiring linesthat cross or just let them cross? I know to add dots where there are connections.I personally like to break thehorizontallines on either side of the vertical crossing lines as my eye can easily scan from side to side but have a little trouble following the lines up and down.The drawing shown does NOT break the lines. Think it would help? It's pretty easy to do in this cool program I'm using (Paint.Net)" alt="" class="bbc_img" />Thanks.

author: moffy
author_rank: Super Contributor
timestamp: March 11, 2024, 10:20:52 pm
content: FYI I was not able to load the image. Just let the lines cross, dots show connections, but good layout as with a pcb is very important.

author: donlisms
author_rank: Frequent Contributor
timestamp: March 11, 2024, 10:32:28 pm
content: The objection to the dot/no-dot technique was about copying or printing with lower quality, and not being able to tell the difference. As the owner of several bad PDF's and mediocre eyes, I appreciate that!The other old technique was/is a little curved jump over the non-connected wire; rather clear and unambiguous, but no longer popular.I have an important early schematic that assumes two lines crossing are not connected, but a "T" is. Hard to read! Thank goodness conventions improved over time.

author: Benta
author_rank: Super Contributor
timestamp: March 11, 2024, 10:39:30 pm
content: Quote from: Vonsgarage on March 11, 2024, 10:11:11 pmTotally non-standard and not recommended.The present-day way is to just let the lines cross.In older schematics, you'll often see a "jump-over" hoop where lines crossed.This was to prevent optical "blooming" at the cross (making it look like a connection) when copying the schematic blueprint (this was back in the paper days). Not necessary today.Just let the lines cross, and place a dot when a connection is needed.BTW: why not just install KiCAD? It's free and a dream for creating schematics.

author: Benta
author_rank: Super Contributor
timestamp: March 11, 2024, 10:43:30 pm
content: HA!Seems @donlisms and I share the same experiences.

author: bostonman
author_rank: Super Contributor
timestamp: March 12, 2024, 03:05:19 am
content: Personally I like multi page schematics meaning:The input AC voltage, transformer, and DC output voltages should all go on one page (unless it's too complex) and the off sheet connections are named according to the voltage.Then (in your case) the motor drive circuit on another page, etc...This way you break down the circuits for others to read easier and less chance of crossing lines. At an old job I don't remember ever seeing crossed lines as a result of multi-page schematics. My current job has absolutely horrible schematics where everything is on one page including drawing the physical look of the AC plug, motors, etc... In fact, the AC plug and motors are drawn very large and it shrinks the schematic so tiny that it's unreadable when printed.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 12, 2024, 06:50:54 am
content: FWIW, in EasyEDA I use a line (as in art, not a track) thicker than a track to "break" the background/less important track.It's tiny, about the thickness of a track in the schematic, and not easily mistaken for a break in the track; and does not interfere with the actual schematic since the "break" is only a visual artwork trick.Surprisingly, when zoomed out the end result is that the crossing looks intact, but clearly different (lighter) than a connection, making it much easier for me to tell the difference when zoomed out. Zoomed in, it looks nice, yes; but the main benefit for me is the zoomed-out "extra-thin" crossing, easily distinguished from an actual connection.You cannot do the same in KiCAD 7 at least, because although it supports such lines (non-wire, non-bus, artwork lines), it does not allow you to rearrange the order in which they are drawn, and always draws artwork lines over wires. Technically the.kicad_schfile format should support this, by simply rendering wires and elements in the same order as they're specified in the file, allowing visual reordering, but I haven't looked at whether KiCAD (eeschema) innards would actually bend to that.

author: Ian.M
author_rank: Super Contributor
timestamp: March 12, 2024, 06:53:26 am
content: Crossing lines should *NEVER* be a joint.

author: Vonsgarage
author_rank: Contributor
timestamp: March 12, 2024, 09:33:58 pm
content: Good evening my friends!As always, the best site on the planet to get the correct answers.Ian.M: Got it. I had one instance of this this situation and have corrected. Thanks. Look up in the left corner in the Capstan Motor Power Supply ground rail.Nominal Animal: Good advice. I can see how it would be helpful to highlight voltage rails and audio signal paths.bostonman: I have already seen this issue and have gone crazy with this reel-to-reel owner’s manual. I have completely redone all the schematics and changed the resolutions. I have created all new PCB x-rays of all the PCBs. Even the two-sided PCB’s. In Color! BTW; I remember having to use schematics from the Netherlands (Rademaker Bakery Equipment) back in the 90’s. I guess you all would consider them easy as it was almost all analog back then. Still tricky to me. Especially when the pressures on as there are 50 Union bakers standing around, on the clock, when the line takes a dive.Benta: Crossing lines; OK. Will do. I had forgotten about the “hoop” crossovers.donlisms: Print quality is why I was wondering about the line breaks. But I guess in this day and age we all have good printers.moffy: I will try just attaching the image this time. I tried to insert it in-line with the post. 1.2M PNG format. End of Post. OK?

author: Smokey
author_rank: Super Contributor
timestamp: March 12, 2024, 11:05:39 pm
content: I almost never cross traces that are not actually connected on a schematic. I'll just use ports instead of cross traces, which I think is more readable anyway. It's just a personal style since things end up being electrically connected correctly either way.If your cad software does the "wire jump" cross over automatically, it's much less of an issue I think:Another thing I do is make schematic symbols in a way that will minimize crosses when used. Like don't burry an enable pin between two other pins you know will have a resistor between them such that you have to cross the enable line over the resistor or the other lines. Just put the enable Pin at the top of the symbol where you know it can get routed cleanly.

author: fourfathom
author_rank: Super Contributor
timestamp: March 12, 2024, 11:10:35 pm
content: Quote from: Ian.M on March 12, 2024, 06:53:26 am100% agreement. Perhaps it's no longer the issue it was back when we were using actual hand-drawn and blueprint-copied schematics, but those "dotted cross" connections still makes it harder to quickly review a schematic. It's not the dot so much, it's the structure.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 12, 2024, 11:39:19 pm
content: There are those who will die on one hill of formalism over another. But remember the goal is ease and clarity of reading.I grew up in the day when the jump-over hoops were preferred. And for me they aid greatly in many cases. But become an ugly sea of confusion in a schematic which has many crossing lines in a confined space. A situation that is far more common in digital circuitry than in the older analog circuits.Your audience is as important as anything else. The automotive industry has a style that works great for those in the field, and drives those outside crazy. But if you are drawing automotive schematics that is the "right" style to use. Power distribution has its own set of rules. There are many other style pockets. And remember that if you are drawing the schematic you are perhaps the most important audience. Particularly if you are doing hobby work and few others will ever see your schematic.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 13, 2024, 01:05:34 am
content: Quote from: Ian.M on March 12, 2024, 06:53:26 amYes, it avoids potential mistakes when designing and potential confusion when reading.That said, in some cases, a common joint is more "idiomatic", like when placing 2 clamp diodes. Sure it's still readable if separating the two lines even in this case.But, as always, let your common sense guide you.

author: ajb
author_rank: Super Contributor
timestamp: March 13, 2024, 08:32:05 pm
content: Quote from: SiliconWizard on March 13, 2024, 01:05:34 amNot sure if it's still a problem, but I have seen Altium remove connections at crosses like this when rearranging schematics. It would be very easy to miss that and end up with a bad board, which is a very good reason to avoid the practice when using Altium. That said, I will place clamping diodes in line from each other as you describe, but only if the end of the pin lands on a wire, since that will ensure that a connection is made. If the pins can't land on the wire for space reasons or whatever, then it's back to offsetting the connections.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 14, 2024, 03:13:47 am
content: I try hard to avoid four-way connections too. Having the background wire "break" passing a foreground wire is not an alternative to that! It's anadditionalmeasure, to further reduce cognitive load.TL;DR: As an example of how well that works, check out Paul Stoffregen'sTeensy schematicsat PJRC.com.The underlying problem is, when youreada schematic, you cannot know how hard the author avoided crossings looking like connections.The only things that actually matter is 1) that the schematic is functional and correct, and 2) perceived as intended, correctly understood when viewed. (Professionals have additional points, of course; I'm just a hobbyist.)For me, wire crossings –– connected or not –– present unwanted and excess cognitive load, even in my own designs after a week or more.As a hobbyist, Ireadschematics (especially in datasheets) orders of magnitude more often than I draw them myself, so I don't have an automatic "ah, this is drawn usingtheserules, so no need to worry about crossings looking like connections" switch in my brain at all.I use the line art trick to reduce that cognitive load. Avoiding four-way connections reduces it even further; the two work well in combination.I am just not wise, experienced, nor intelligent enough to have my brain/perception do it all efficiently without such help, and need to use such tools to help me understand.The underlying reason for why I choose to do that has everything to do with human perception and my decades-old interest in generating visualizations that convey the desired, controlled, information. For example, when displaying atomic models, instead of going for pseudo-photorealistic imagery (as if atoms were spheres connected with rods, or metaballs), you can convey the understanding of a complex structure more effectively using graphic art tricks: stuff like color perspective (to simplify, blue implying higher distance than red), cel shading, and using outline/intersection line thickness to describe depth separation.The "disconnect" is visually based on depth perception, with the background thing being "blurred" compared to the foreground thing in focus, with the part in human perception that enhances edges causing a difference that can be emulated by one of two lines crossing break just before the crossing.Thus, it is not just a matter of having two separate symbols, one for connection and the other for no connection; it goes deeper into human perception than that.The first books I read about electronics and schematics used half-circle jumps at non-connected crossings, but I found those not any better than the alternatives wrt. my cognitive load –– so having explicit "connection" and "no connection" symbols did not help me much! ––, and seeing the first schematics with tiny breaks (not more than line thickness!) I realized the issue, and found that helped a lot, and adopted it immediately. (When sketching circuits on paper, I still "default" to half-circle jumps, even though they're much less useful than the tiny "breaks".)A good example of this well done is Paul Stoffregen'sTeensy schematics. One may not even realize non-connected crossings have the wire beneath "break" around the foreground wire; you just automaticallyperceivethem correctly/as intended.Funny thing is, this would betrivialto implement automatically in a schematic editor, by simply drawing each wire link twice: once using background color at 3× line thickness, then using the link color at 1× line thickness. That is exactly what I do in EasyEDA, with the background one being line art and not a wire, except only at the crossings. (I also do stuff like use invisible/background color for wire labels, since I don't need them in the schematic, and just want descriptive track names when drawing the PCB. Only a small × is visible on the wire in the schematic; when hovering on top of that, the wire label pops up, so one can view and edit it when necessary; it's just not shown all the time in the schematic.)Note: I am not recommending others do this too, or any other thing either: I don't have enough experience. (Based on what I know about human perception, I think so, but I am not certain/convinced yet.)I only do this –– avoid four-way connections, and use tiny breaks on the background wire to enhance perception of non-connected crossings –– because it really does help me parse the schematics correctly.

author: fourfathom
author_rank: Super Contributor
timestamp: March 14, 2024, 03:34:04 am
content: Yes, it's idiomatic, and we can more easily interpret what we are used to seeing. I for one never use a crossed connection. and when I see a cross I automatically assume there's no connection -- even if there is a dot. A bit later I notice the dot and I have to revise my understanding of the circuit. This is an error-prone mental process. When reading a schematic I like to first understand the forest, and only later look at the individual trees.In a similar vein, I truly dislike it when people run a ground schematic wire vertically, and connect to that using horizontal wires. It's certainly not electrically wrong, but it's jarring and confusing, requiring extra effort to understand. For me, anyway. Style matters when trying to convey information. I know we don't have one truly common style, but I wish we did.Some projects I have worked on essentially eliminated schematics. These were boards with several 1000-pad BGA ASICs, and we ended up generating the necessary schematics programmatically, ending up with blocks having nothing but the netlist names. We had higher-level documents that included graphic representations of connection classes, but the netlist was the master document. Not my favorite schematic style, but there were good reasons for going this way.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 14, 2024, 05:58:27 am
content: Quote from: fourfathom on March 14, 2024, 03:34:04 amVery much, indeed.Many ofminecurrently end up using net labels around functional units, exactly because even though I know many of the rules of thumb for making good schematics (horizontal rails, preferably vertically sorted in order of voltage with most positive topmost, and so on), I don't have the experience to apply them effectively to make the schematic easily readable. Its one thing to know the desired results, and another to get there! Me, I'm still in the Lego phase wrt. schematic design, constructing larger combined schematics from smaller circuit sections I can understand (and often have simulated).I think net labels work when they separate different functional units, but when used as much as I did for example forthis dual 12V PWM fan controllerboard, it makes it hard to perceive thewhole. It makes it easy to perceive the implementation detail (two channels of open-collector PWM outputs, two channels of 12V pull-up tachometer inputs), yes, but it is like seeing the individual trees but not seeing the shape or density of the forest. Very non-optimal. Functional, yes, but definitely not an example of good schematic representation of the circuit.My first designs were carrier boards for microcontroller development boards, for which I drew schematic symbols that corresponded to the MCU board layout. Now, with a bit more experience, I don't like that, because it is really relevant only at the PCB stage, not when trying to represent the functionality or the system at the schematic level.Thus, when recently playing about with a PWM-driven voltage tripler circuit for generating the 12V programming pulse for AVR UPDI programming interface, to make the circuit look more familiar (instantly recognizable as a voltage multiplier) at the schematic stage, I created a custom BAT54S,215 schematic symbol with the two consecutive Schottky diodes diagonally. (EasyEDA only supports rotation in 90 degree steps for schematic symbols.)To my surprise, I now understand that it would be very useful to have more than one possible schematic symbol for each component that one can choose from, depending on what makes the particular schematic easiest to understand. For modules like MCU development boards, omit pins not relevant to the design by deleting them from the schematic symbol instead of just marking the pins unconnected.(Just consider if the UI of KiCAD eeschema was written in Python, with all the actual data manipulation in a dynamically linked native library, so that one could simply experiment with a completely different schematic symbol library interface without having to recompile the entire package. In some cases, you only want a generic symbol, sometimes a symbol suitable for a specific IC, in others, a completely custom one-off one. This is why I've talked about that approach for userspace applications in the Programming sub-forum here: it makes experimenting with this kind of stuff very feasible in real life.)If the experienced designers here ever write style guides, I would warmly suggest they alsoexplainthe reasons for the choices.That kind of knowledge only comes with real-world experience, and makes a huge difference to those who are interested in developing their skill, as opposed to just following a ruleset.Anecdotal examples of making opposing choices in similar design situation, and their results thereof is immensely useful, because it provides context making it easier to slot the advice into ones existing understanding. Learning rules related to creative work by rote is in my opinion pretty much useless, because there are always situations when breaking a specific rule yields better overall result than following such rules blindly.

author: Bud
author_rank: Super Contributor
timestamp: March 14, 2024, 06:27:42 am
content: Broken lines are fancy and unnecessary. And you cant use that style in a CAD for PCB routing, as there will be no electrical connection.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 14, 2024, 07:30:45 am
content: Quote from: Bud on March 14, 2024, 06:27:42 amWe're talking about schematics, not board design. In schematics, I've described adjusting how crossing unconnected wires aredisplayedas if broken, but are fully continous in the schematic and electrical connection sense, by using line art and modifying the object drawing order. Electrical connections are not affected by the line art, and e.g. Design Rules Checks and net lists stay fully functional.This cannot currently be done in KiCAD, but is trivially done in e.g. EasyEDA.

author: Vonsgarage
author_rank: Contributor
timestamp: March 14, 2024, 10:03:20 am
content: I visited Teensy Schematics and the first thing I saw was a missed line crossing clearance. Makes another good argument for just letting the lines cross.I think the majority have agreed that the line breaking is first to be avoided and second not to be done.And Now for Something Completely Different: PCB X-Ray Views.What are your opinions on what graphics should be shown on these? Components shown clearly and "on top"? Shown symbolical as there are on schematics or more close to their actual shape? Component values shown or just part numbers? Solder side down / component side up everytime? Shading or color recommendation for component side foils vs solder side foils?

author: Vonsgarage
author_rank: Contributor
timestamp: March 14, 2024, 10:19:34 am
content: BTW;Nominal Animal;This is an excellent, excellent book that describes similar concepts that you so astutely described. Perhaps you have read it?Envisioning Information by Edward R. Tufte

author: bostonman
author_rank: Super Contributor
timestamp: March 14, 2024, 01:39:25 pm
content: I also noticed an open node below L2.As for crossing lines, four way connections is wrong (I was told this long ago) which is why they are offset rather than looking like a plus sign.Personally I'm against crossing lines, however, sometimes it's needed due to space like several connectors are all in line, and, rather than draw separate grounds, one long line cuts through all the data lines connecting to a single ground.I'm also against schematics with ground symbols sideways or upside down in order to fit into an area. Battery and ground symbols should be vertical.As I previously mentioned, I'm a fan of several page schematics. It makes things much easier to follow for things like a power supply and/or DC voltages on one page. This way you know which voltages are on the board, which voltages feed them, etc... If the unit is being repaired, the first thing you can do is look at the power supply schematic page, see all available voltages, and measure them.

author: MarkT
author_rank: Frequent Contributor
timestamp: March 14, 2024, 08:48:22 pm
content: a.k.a. "separation of concerns", just as applicable to hardware diagrams as software design...

author: fourfathom
author_rank: Super Contributor
timestamp: March 15, 2024, 06:10:14 am
content: One trick I use takes advantage of our learned schematic style idioms. When you are having a hard time figuring out a problem, take the schematic and turn it upside down. This disorients you enough that you no longer see what you assume is there, but forces you to actually study the connections. I've helped non-engineers figure out their boat wiring problems using this technique. This is especially useful when someone has been taking the ground symbols as gospel. By making it appear as just another net (not being in the "standard" location), they start understanding that this connection might not be as solid as they assumed -- which is often the case, especially on boats that live in salt water.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2024, 07:16:01 am
content: Quote from: fourfathom on March 15, 2024, 06:10:14 amI cannot help myself.Howdoyou ground a boat, anyway?

author: JohanH
author_rank: Frequent Contributor
timestamp: March 15, 2024, 07:28:44 am
content: Quote from: Nominal Animal on March 15, 2024, 07:16:01 amI am not a sailor, but I've heard them call it a galvanic anode or sacrificial anode. That must be it.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2024, 07:37:51 am
content: Sacrificialanoppi? Now this needs further investigation, definitely.

author: JohanH
author_rank: Frequent Contributor
timestamp: March 15, 2024, 10:03:24 am
content: Quote from: Nominal Animal on March 15, 2024, 07:37:51 amI can assume at least some women agree to the idea to drag their mother in law after the boat attached to a "ground wire".

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2024, 12:20:57 pm
content: I recall Nik from Bad Obsession Motorsport mentioning in one Binky build video that some car or other had an insufficient (current capability i.e. too-thin) ground/return wire from the rear end lights, causing issues when you had brake lights and hazards or blinkers on at the same time. Even though the chassis is at the "ground" potential, it isn't normally used for reliable ground/return currents.I can understand a little bit about star grounds, especially when a "limb" is a different subsystem on a microcontroller, say analog used with built-in ADC, or some digital signaling ground vs. high-power motor ground. The filtering between these (especially the resistor-capacitor parallel connection) is something I need to learn more about. I do know that in cars because of starter motor current draw causing significant voltage drop and alternators and occasionally corroded connections causing voltage spikes and whatnot, "automotive" supplies tend to be much more robust against nominally 12V supply noise than ordinary DC-DC supplies.In a marine environment, I can imagine the electric fields (during thunderstorms) can become significant even in a metal-hulled boat, and cause all sorts of grounding issues; just seeSt. Elmo's fireas an extreme example.How do you separate such "different grounds" (even though they're basically all at the same potential, only the return currents through each differs, wildly) at the schematic level? Just use different net labels? Where and how to best show their single-point connection (or whatever one might have)?

author: TimFox
author_rank: Super Contributor
timestamp: March 15, 2024, 04:14:29 pm
content: Galvanic or sacrificial anodes, q.v., (typically aluminum, zinc, or magnesium) are used to protect metals submerged in salt water from corrosion.The anode material is consumed in the protective reaction.

author: fourfathom
author_rank: Super Contributor
timestamp: March 15, 2024, 04:21:49 pm
content: Grounding on boats and Sacrificial Anodes:There are a few different types of "grounding" on a boat. Metal hulls (steel, aluminum) have their own issues, but I'm going to discuss a typical fiberglass-hull vessel (such as my sailboat).1) House Ground: Internal connection between battery-bank(s), charging systems, and "house" electrical / electronics such as radios, lighting, navigation gear, engine, etc. This is the grounding I was thinking of when I mentioned turning the schematic upside down. The battery bank often has a current-shunt between the negative terminal and the system common ground. There may be no connection to the external water (more on this later). Ground connections are made with wire, lugs, terminal strips or posts. Some connections have to carry a lot of current (such as the engine-starter motor). This is all pretty similar to a car's electrical system, but usually with a lot more gear.2) RF ground: Used for HF radio, usually SSB (voice and digital). Most sailboats use an insulated back-stay antenna (the backstay is one of the heavy stainless cable that keeps the mast from falling over). This acts as a non-resonant end-fed vertical antenna, and is fed by an Antenna Tuner Unit (ATU, usually automatic). For this vertical antenna to radiate it needs a groundplane or counterpoise, and salt water is an excellent groundplane. The RF ground can be a metal through-hull (used to bring engine cooling water in or discharge water out of the boat), the metal keel, a specialized ground plate on the hull, and/or a copper screen groundplane embedded in the hull lamination that is capacitively coupled to the water. These only work with salt water, fresh water is essentially an insulator. Freshwater systems usually use a counterpoise system inside the hull, but there are few marine radios on freshwater boats. The RF ground is often isolated from the boat's "house" ground bu capacitors (see below for the reason).3) Shore-Power and Sacrificial Anodes: A boat has external metal parts (propellors and propellor shafts, through-hulls, RF grounds, other hardware), and these are often made of different metals. Bronze and steel being most common. If these are connected by a common ground (or otherwise) then when immersed in salt water you have a battery, driven by these metal's relative place in the galvanic series. This causes one metal to lose material, plating the other. Sometimes you can't avoid this, as when you have a bronze propellor attached to a stainless shaft -- the unprotected propellor will essentially dissolve over time. To prevent this we attach a "sacrificial anode" to the external metal, usually zinc or aluminum. These are the first to dissolve, sacrificing themselves to protect the other less-reactive metals. When a boat is connected to shore power this gets even more complicated, as the shore power has it's own ground, as do any other nearby boats also connected to shore power. We often put a "galvanic isolator" in series with the shore power ground wire (this is usually a couple of back-to-back diodes), which still provides a safety ground if the voltage difference exceeds a couple of volts.As you might guess, there's lots of confusing and conflicting advice on all this.