Schematic Drawing

[Falcon69]

So, as many of you know, my schematic skills are just HORRIBLE. I know this, and I've been told this...not saying any names....Tim...AKA T3sl4co1l   

So, since he, and so many of you have helped me with my circuits, and the learning process of doing those, design and PCB Layout, I think it is time to try and work on the schematic part of it.

So here is part of my circuit. What would you change, and why? Does it look okay as is? Is there too much Labels/Flags?

 I've tried to make it so each flag represents (the way it is drawn like an arrow) the way the current would flow into or out of said part. I've also tried to indicate on the label/flag to which part and Pin number that particular schematic line would go to.  Unless it is the standard voltage, ground, or other reference (i.e. LED_EN).

Thanks for Any Help: 

[IanB]

The first thing I would do is present a block diagram that shows the information/signal paths through the whole system from input to output, with a name and description for each block showing what it does. For example, "level shifting", "debouncing", "filtering", "latching", and so on (just for instance). Each block will have one more inputs and one or more outputs.

With this overall description of the system in place it will be possible to show the detailed circuit for each block and permit someone to understand more clearly what that part of the circuit is doing. By convention, circuits wherever possible should have inputs and outputs clearly marked and should flow from left to right.

[Falcon69]

but how would you do that when a connector has both in and out on it? (current flow anyway)

I don't understand this 'block' thing you speak of. This circuit is pretty simple, as discussed in another thread. It has just logic gates and hall sensors for triggering.

[Falcon69]

fyi...there are multiple 'sheets' to this schematic. in another thread, it shows the schematic as a complete, but is impossible to follow. you would need a 65" big screen to see it all, wqithout panning the screen.

[IanB]

but how would you do that when a connector has both in and out on it? (current flow anyway)

A connector is a physical thing, and schematic means "not physical". You do not have to show a connector as a single object on a schematic diagram; you can separate the input and output signals and show them in different places.

I don't understand this 'block' thing you speak of. This circuit is pretty simple, as discussed in another thread. It has just logic gates and hall sensors for triggering.

The video linked below shows an example of a block diagram and how it simplifies understanding of something that would be hard to follow at the circuit level.

fyi...there are multiple 'sheets' to this schematic. in another thread, it shows the schematic as a complete, but is impossible to follow. you would need a 65" big screen to see it all, wqithout panning the screen.

This is exactly where a block diagram helps. When something is huge and impossible to follow it needs simplifying.

https://youtu.be/dwAieDTRMdQ?t=18m49s

[Falcon69]

So, in the video, everything in the dotted lines that make up the circuit, is a "block" of that schematic, and that would be what I would put on a separate sheet of the schematic file?

That makes sense, however, like I said, the schematic is HUGE with all the circuits and sensors.

Okay, That's good, I can take out the connectors. I guess, Actually, since I need to convert this to PCB later, I'll just move the connectors off the sheet, so When I print them, they will not be on the sheet, but will still be in the schematic file.

So The little flags.....would I show where they go, like if it is going from Sensor_1, pin3 to U53.3 (logic gate #3 in a 4 gate chip) pin4...i would word it as "to U53.3_4"?  For example?  Instead of it going to the connector? Just bypass the connector all together on the label, and treat it as if there were no board to board connectors and it is just one giant schematic.?

[zapta]

Having the diodes floating in the air hanging on a single wire is strange. I would draw them vertically with the GND and VCC connections.

Instead of naming the signals by the connector pins and using arbitrary colors, I would name by the signal function.

Having those big arrows for connecting wires require spacing wider than the input connector pins. In Eagle, I would just draw them as horizontal wires, with the same spacing as the connector pins and have the net name shown on each one.

The thick green borders are distracting IMO.

You can see an example here for my subjective preference https://github.com/zapta/arm/blob/master/pro-mini/board/arm-pro-mini-schematic.pdf  .

[Falcon69]

ya. those TVS diodes confused me as well. I didn't know how to draw them.  If I add pins to allow for VCC and GND, it would have too many pins on the chip when I convert it to PCB. Those chips are actually 4ch TVS diodes.  Unless I can make the same pins appear on the same part in the component editor of the schematic.

I did the green border, because I thought that would be a better way to separate the circuit from the others on the page?

So no arrows, just a Net name on them?  The arrows were more of a help to me as well, it showed which way the current was flowing. for me it was easier to understand.  But the whole point of this discussion, is to teach me to draw an acceptable schematic for others, NOT for me, to understand.

Signal function?  I still don't understand how to do that, are what you mean by that I looked at that video, I have no idea what frequency (or whatever) that each of these signal wires would operate on, nor if they are even relavent to this circuit, since most of the entire circuit is just analog (just logic gates and hall sensor, no microcontroller and such).

[Falcon69]

Zapta,

On your schematic, the TP20~ writing on the end of the lines with the circles...that would indicate a jumper point, or rather, a header pin like I have?

[IanB]

The block diagram in the video is for a system quite different from yours. It just happened to be the first example of a block diagram I could recall. I wanted just to illustrate the concept.

On that diagram, the blocks have a particular function, such as "amplifier", "mixer", "splitter", "filter", "switch", and so on. Each block is represented by what it does, not by how it is made. By joining up those building blocks and showing how the signal is conveyed through them it becomes possible to show the functioning of the complete system.

Each block is actually built out of more primitive circuit elements (resistors, capacitors, transistors, ICs) that would actually appear on the circuit schematic.

The block diagram from that video can fit on a single page and can be followed by a someone tracing through it, as Shahriar showed. The full circuit schematic would be much larger and more complex, and would be hard to follow without the block diagram as a guide.

For your particular circuit, you should I think be able to describe what it does from input to output. You take one or more input signals, you do something with them (buffering? combining? delaying? switching?, ...), and you generate one or more output signals. Even if you don't have a block diagram, your circuit schematic would still benefit from having a continuous "flow" from inputs to outputs, rather than being shown as several unconnected panels.

[Falcon69]

okay, I'll try working on it.

I just need to figure out how to do it now, without messing it all up when I go to convert to PCB.

[IanB]

Have a think about it certainly, but don't take what I say as the last word.

What I can say is that when I have reverse-engineered a PCB and drawn the schematic from it, then very often the layout of the traces on the PCB bears little resemblance to the arrangement of the schematic. So a good schematic entry and PCB design program should allow you to completely separate the layout of the schematic from the layout of the PCB.

The schematic should show the "logic" of the circuit, and the PCB should show the physical layout of the components and traces.

[Falcon69]

i welcome all input IanB   thank you

ya,  i understand the separation between schematic and pcb. however, there is still an Art and a learning curve for creating both of them properly.

[T3sl4co1l]

Channel 1/8?  Consider using hierarchical design.  You can repeat schematic sheets, and repeat the PCB layouts at the same time!

They are a bit more confusing to use, as the designators are separated into logical (e.g., R101, R102, ...; what's on the schematic sheet) and physical (R1101, R1102, ...; R2101, R2102, ...; ...; what's on the PCB) designators.  The designators can be customized or auto-generated.

Multi-part components don't split nicely over channels (consider why..), so it's better to use single parts (SOT-23 gates, op-amps; single clamp-diode pairs; etc.).

Tim

[CatalinaWOW]

A schematic is a conversation between the designer and others.  The others may be a future version of the designer, a technician, a student, a buyer or a variety of other people.  Schematics ideally would take a different form for each of those recipients, but that level of effort is almost always way too much.  So it is always a compromise.

Each audience will interpret schematics based on their tradition.  That is why automotive schematics are so different from most electronics schematics, and also why they seem so incomprehensible to most electronics background people.

All of this leads up to:  the best schematic will depend on your audience.  The audience here is telling you how to talk to them, which may or may not be what you want.

[suicidaleggroll]

Personally, I don't like the labels having "_IN" and "_OUT" appended on them.  Let the arrows do the talking, the label name should be common across the entire schematic.  If I want to see where all a labeled signal connects, I'm going to hit ctrl+F, type in the label name, and I expect to see all of them.  I don't want to have to alter the string I'm searching for depending on whether it's an input or an output or what page it's on.  And how am I supposed to know that your S1_IN and S1_OUT are actually connected to each other since they have different names?  For all I know those are completely different nets.

[Falcon69]

So, I had a chance to work on it alittle bit.

I think I figured out the Hierarchy block thingy.

Here's what I have so far..Better?

I left off the title, etc. I didn't cut/paste the whole sheet, just what was on the sheet.

[T3sl4co1l]

You don't have to subdivide it so heavily... the main purpose is to reuse sections that repeat.

Hm, U2 is missing a comment.

Tim

[Falcon69]

Okay, I will merge the Rev. Polarity Protection, 5.0V, and the 5.37V into one block.

If I do all three separately on the main sheet, there will not be room on the main sheet to do the rest of the stuff.

And I fixed U2, thank you.

[Falcon69]

Welp, I had alittle more time to work on my schematic.

i have changed all the tags/labels to represent the net they are tied to, not the In/Out like i had it. You guys were right, that was confusing.

The arrow (shape of the Tag) defines that anyway going in/out of the connector or particular part.

I know this is not the conventional way to do schematics, but for me, this is easy to read and understand.

The D79-D82 don't show the power connections individually. I had to make a separate power/gnd connections under the 'PWR CON' as the pcb software messes up when trying to import it to PCB.  This way, it keeps it neat and tidy when importing.

That Blank Box you see will be for notes and such. I just have not written any.

To me this seems to work. I can label all the nets with a "RP" (for rear panel) at the end of each net when I rename them. That way, when I import to PCB, it will keep all the nets separate for that circuit board, as there are multiple boards for this project connected Via headers or other connectors, with each having similar net names.

So, look better now? More easier to read/understand than previous drawings?

Please excuse the jpeg file.  It was a Snip using the windows tool. It isn't the best. But, when importing to PDF, it is very clear.

[Falcon69]

EDIT: I've added the power and ground connections to those TVS Diodes so they don't just sit in the air, as Zapta suggested.  I figured out how to do it so when it converts to PCB, it doesn't add extra pins.

So, How's it look now?

FYI, this is just one of 11 circuit boards in the project I need to draw a Schematic for.  Luckily, I only have to actually draw 4, because there are 8 Identical ones out of that 11.

[Falcon69]

Oops, forgot to post the schematic. I did it in .pdf this time, it is much clearer.

[rstofer]

That looks really neat; the part I can see...

A significant segment of the adult male population (1 in 12) has defective red/green color vision.  So, the black on yellow labels are easy, the black on gray are workable, the green on pink might as well be blank (I hope I got those colors right!).

https://ghr.nlm.nih.gov/condition/color-vision-deficiency#statistics  look at the Frequency paragraph.

Don't change the colors on my account but it is something to consider.  I particularly like the directional flags; I use that scheme myself.  The coloring adds a lot of context but, for me, the green on pink is a problem.  Maybe black on pink?  I don't know...

[Falcon69]

Thank You estofer.

I never thought about the color blindness thing. I will change the colors.

[TSL]

As one of those red/green color confused guys I always appreciated the efforts to include us. Suffice to say I had to measure every through hole resistor I've ever used to make sure I had the right values. Same goes for other color coded stuff.