Schematic preferences

What about gates? All subcircuits get power pins? What about dual op-amps?

Again, that uses a additional "wiring channel" on the sheet. Dots work fine.

We use the triangle for analog grounds. A triangle with an "F" for "field" (isolated external) grounds.

Yes, and

| --------- ----- -

is a digital grounds. I know, they analog and digital grounds _should_ be the same. They will be soon. ;-)

Shields?

We put general notes where they fit and specific circuit notes pointing to the device or circuit they're describing.

We do that, sorta. Identical channels are numbered R1xx, R2xx,... Rnxx, no matter what page they're on. In one schematic four channels are on pages 3-7, but are still labeled R1xx for channel 1.

I also like Larkin's reference numbering from side to side with the schematic being back-annotated after layout. That really helps debug.

Are you claiming to be the last drafting droid? ;-)

Busing isn't useless though. I like to draw equal signals across, like this for instance:

The AC supply isn't the kind of thing you want wires hooked to globally, so I would hesitate to assign named connections to it. It's a small circuit, so it's not a big deal, and the buses stayed short. I could assign ground to the output side, but decided against it. That would avoid the ugly drop below the rectifier-filter, and maybe the IR LED connection could move somewhere.

Other than that, I think my only complaint is this drawing doesn't have a pleasing aspect ratio -- it's just too wide! The more primitive model isn't as balanced, but it does have a pleasing ratio:

This one is heavily bused:

I'm pretty sure I would draw it differently, but I may also retain the buses. It doesn't seem right to label them seperately; the circuit is closely connected, and yes, it is representative of the layout (which was breadboarded).

One more example, a larger one:

For its size, I broke up the building blocks, putting lots of white space between them. The components are fairly tightly spaced, as was my style at the time. Signals weren't cleanly bused, like how R315 and 316 aren't in line, that looks kind of weird. D308 is actually carrying a signal backwards, but it's only a little ways, towards a common node, so it's not too horrible. The supply lines are locally bused in some cases, and floating in others (IC301 south, R314, etc.), which looks kind of sloppy, maybe or maybe not worse than the alternative (studded with +V's just looks too redundant).

Someone mentioned feedback paths can be reversed. Setting aside "I know what you mean", would this control circuit be acceptable to mirror, just because it's a feedback circuit? ;-) The obvious answer is, only if the rest of the loop dominates the circuit.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

"Jon Kirwan"  wrote in message 
news:ff5al512h08e7ome836c0d36efcfe3obnk@4ax.com...
> Just by way of example, here's a poorly laid out circuit:
>
> http://www.swtpc.com/mholley/PopularElectronics/Nov1967/PE_Nov_1967_pg30.jpg
>
> In my opinion.  Find the +rail and ground lines and trace
> them around the schematic.  What's the point in the busing
> everywhere?  How much do those 'wires' interfere with
> following function?
>
> Now, if you are point-to-point wiring stuff you might lay out
> things and then run the heavy wire around like that,
> soldering to it along the way, I suppose.  Maybe.  But if you
> are trying to follow the operation with understanding there
> are better ways to draw it.
>
> It's not the worst example around.  But it addresses some of
> the points.  Emitters from different PNP's pointing
> differently.  Emitters from NPN and PNP pointing the same
> way.  Bus wires trapsing around all over the place almost
> looking as though they might carry signal.  Etc.
>
> Jon

That's how I used to draw things. But, I found it often resulted in clumsy signal routing -- just to avoid a 4WS.

I don't worry about people adding dots to *my* drawings. :>

The bigger worry I have is when schematics are reproduced and it becomes difficult to determine if there is or isn't a dot on the junction.

Ditto. The problem I find with EDA tools is they don't let you put "tags" in text on the sheets. E.g., if you have a note: "D1 - D4 installed on heatsink" and you backannotate the schematic, D1 may no longer be D1, etc. So, you have to manually go through and update the notes. It would be nice if you could set up cross reference tags like in DTP tools...

My main rule (a preference actually) is that the same name be used in the callouts when a circuit involves several schematic sheets!

I once worked for a video company that had a PLL circuit that traversed 6 or 7 different circuit boards. I guess each engineer / designer was responsible for his own board, because none of the names matched up. This made final device test & calibration very difficult.

This device comprised roughly 75 "D-size" sheets of schematics. I can still smell the ammonia from the Diazit copier..

We haven't done that since the 1980s. The technicians were the ones that suggested the change. We used to do boards with things like RA12 meaning column A row 12.

3

For issues like that: Put "NOTE 1" next to the parts on the heat sink with a dashed outline Then make NOTE 1 say "These parts are on the heat sink"

One of the parts of the op-amp show the power pins as does one logic gate.

Dots have lead to errors. If the reproduction of the schematic is less than perfect a mere fly spec can send the technician down a blind alley.

[... ground symbols ...]

What do you use for chassis ground?

You mean you don't flaot all your logic on the +5V plane?

------ -----! 7805 !--------+--------- Logic Vcc ------ ! +----------------------- Logic grounds ! /---/ 5.1V ! +----------------------- HC4051 Vee connections GND

I really did do this and the technicians didn't even kill me for it. I avoided adding a switching device to make a minus supply for the Vee and the minus swings.

Shields are soldered to "mounting holes" and schematically show as a dashed line running through the hole and around the area.

--
I can't imagine why, since this: (View in Courier)


.          |
.          |
.----------o-----------
.          |
.          |

easily resolves to:

.          |
.          |
.----------o-o----------
.            |
.            |

or:

.          |
.          |
.----------o           
.          |
.          o-----------
.          |
.          |


>I don't worry about people adding dots to *my* drawings.  :>
>The bigger worry I have is when schematics are reproduced
>and it becomes difficult to determine if there is or isn't
>a dot on the junction.

In PSpice Schematics...

Typing /SIGNALNAME/ shows on the schematic as an overbar.

In the netlist it appears as SIGNALNAMEbar ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

It's so cold the Democrats have their hands in their own pockets.

IIRC (my copy is at home) an appendix to AoE also makes this recommendation. Of course, the Appeal to Authority isn't much of an argument in and of itself.

It does sometimes look more "natural" to connect at crossings (e.g., the canonical voltage divider, top to bottom, with a signal passing "through" the junction left to right) but adding a small jog there is a small price to pay for the avoidance of ambiguity. A "T" always connects; a crossing never connects. And no humpies.

--
Rich Webb     Norfolk, VA

--
Indeed, but when the reasons for the adoption of the standard lead to
the lessening of ambiguities and the elimination of errors, then
authority at least got that part right. ;)

That is a _power_ supply. Sometimes, the signal _IS_ the rail. However, that is still one I'd still draft somewhat differently.

I'm very much with you on that point.

It would probably help clarity.

It does seem to need a change. The +rail tie is back a little from where it means more (closer to the 2N3906 which diverts its current) and not more to the left of the 470 ohm resistor which really isn't as related to what is happening there. Plus having both lines crossing over the ground rail line like that...

I don't think I would decide that a schematic is better or worse on the X vs Y size of the plot. Okay, if it is 10 pixels high and 50,000 wide I might question something there. ;) But it's not something I worry as much about as keeping signal flow moving left to right, electron flow bottom to top.

I'd definitely draw that differently.

Let me add some really simple points.

This is a very basic, 1st year degenerative ac-coupled voltage amplifier circuit. I don't like the way it is diagrammed. Not because I can't instantly recognize it today. But because I can remember what it looked like to me when I was first looking at such things and trying to understand them (I've never taken a single course on electronics in my life -- not then, not since.)

At the time, I was looking at publications like Popular Electronics back around the early 1970's. I would see the wires going from the top of R3 to the top of R2 and would incorrectly imagine there was some kind of signal there that I didn't understand. It was only _later_, in one of those random insights that sometimes dawns on one, that I suddenly realized that a rail is a rail is a rail and that signal doesn't happen there. Can't, one hopes most of the time.

Suddenly, I decided to redraw it this way:

Once I did that, the _wires_ no longer made me think about signal. I could easily see that these were _fixed_ values where I could _completely_ ignore the underlying "connection" to the rest. It allowed me to isolate my thinking into much smaller bits to analyze individually. And that was a very sudden and very beneficial insight. Keep in mind I had no one to talk to, no one to ask questions, no one to _give_ me this insight. I had to find it on my own.

Once I started redrawing things according to this new rule, I was in high cotton, indeed. Suddenly, circuits that had seemed so far, far beyond me, were much more accessible. Because I could divide and conquer and didn't need to go tracing my fingers around.

Today, I have other reasons now, though. For example,

Assume that break in the line to R5 makes it so that R5 isn't immediately visible on the sheet. There is much more circuitry there and R5 is ... somewhere. Now I have to go and trace that R2/R3 shared node around to find out if it goes to a rail or something else, like R5. I shouldn't have to do that, if it goes to a rail. That line might instead have been bused over to a +15 voltage source, for all I can tell, but I'd have to trace it out to find out, if so.\

It's just WRONG to do that. I take a second or two or three more of my time. Besides that, the wires just lay all over the place, distracting where they shouldn't when I'm tracing some _other_ line. And I don't appreciate the waste of my time for silly things that do NOT affect the meaning of what is going on locally.

There are times when it is _important_ to bus a rail. But it needs good justification on some important issue worth the cost of readability.

Now you might argue with FIGURE 1 and my statement about having to trace wires elsewhere, telling me that FIGURE 1 doesn't require that and any idiot needs go no further than what they see right there to know exactly what is going on. But if you say that, remember my own story when I was first just starting to try and learn some electronics on my own and my own confusion imagining that _every_ wire was meaningful in some way to understanding what was going on; that signals passed along all wires in some way that I needed to fathom. Put yourself into those shoes for a moment, too. It's not easy. Not even for me, trying to remember what it was like. But I remember enough that I can recall the sudden kicking myself in the head once it dawned on me. I know that it made a difference to me then to redraw, in order to understand. A BIG difference. Not small.

Jon

We sometimes did that for classic arrays of TTL cans.

One division of GE just used a number for the designator; 94 might be a resistor, 95 a capacitor.

The opposite extreme is amateurs that make up prefixes... TR for transistor, RV for pot (RV actually designates a Recreational Vehicle), LED for LED even!

Most annoying, especially when combined with the dreadful 2K7 notation and the accompanying bad circuits.

John

I still have and use a D-size diazo copier!

John

Gag! Reminds me I was responsible for running such a machine during a summer job when I was in high school (1957). ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

TR and RV are arguably signs of not being familiar with industry standards. LED I could imagine someone purposely choosing even though they're well aware that normally it's just D, i.e., they believe they're creating an improvement. Whether or not that's really the case is pretty subjective, although it's pretty hard to argue that someone seeing a reference designator of LED23 wouldn't understand what kind of component it is. :-)

2k7 is a European thing. As with four-way intersections, historically there was some decent justification for it (the decimal point easily getting lost in mechanical reproductions), whereas today it's just a personal preference, I suppose.

Good point. With a few macros in your favorite text editor this is pretty easy to "fix," but I can see how that could be more hassle than it's worth.

Our schematics often have many hundreds of nets (often over a thousand) of which typically fewer than 10% are actually named something meaningful (the rest just being NET0001, NET0002, or whatever the software uses by default). How about yours?