Schematic preferences
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From: krw on 18 Jan 2010 23:02 On Mon, 18 Jan 2010 18:11:11 -0800, "Joel Koltner" <zapwireDASHgroups(a)yahoo.com> wrote: >"krw" <krw(a)att.bizzzzzzzzzzz> wrote in message >news:la3al5t9bc0m40iav7app4hr03mqjne341(a)4ax.com... >> Negative active digital signals start with '/' or end in "_n" (leading >> "/netname" gets converted to "netname_n" in an FPGA) > >I prefer xSignalName, but I don't have any gripes about / or _n -- it's more >important that whatever standard someone chooses, that everyone else who then >works on the schematic adopts the same standard. ....particularly in the same schematic. I really don't like prefixes (other than power) because the signal names don't collate properly. A net and its negative should sort together, just as diff pairs should sort together.
From: krw on 18 Jan 2010 23:16 On Mon, 18 Jan 2010 18:39:06 -0800 (PST), MooseFET <kensmith(a)rahul.net> wrote: <snip> >All parts have the power pins shown. The + is usually on the >top. The exception is references and regulators where it is >on the left. What about gates? All subcircuits get power pins? What about dual op-amps? <snip> >I never crossed lines as a connection point. If two lines connect >to another line, they are offset. Again, that uses a additional "wiring channel" on the sheet. Dots work fine. <snip> > >The triangle ground symbol means the circuit ground of the PCB. We use the triangle for analog grounds. A triangle with an "F" for "field" (isolated external) grounds. >The >three line symbol means the connection to the chassis. The one like >this: > ! >----------- >/ / / / > >means planet earth > Yes, and | --------- ----- - is a digital grounds. I know, they analog and digital grounds _should_ be the same. They will be soon. ;-) >Mounting holes are shown if they have electrical meaning. Shields? >Notes go in the lower left corner of the sheet. We put general notes where they fit and specific circuit notes pointing to the device or circuit they're describing. >The reference of a part encodes the page it is on. R307 is on page 3 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.
From: krw on 18 Jan 2010 23:18 On Mon, 18 Jan 2010 18:53:14 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Mon, 18 Jan 2010 19:37:23 -0600, krw <krw(a)att.bizzzzzzzzzzz> wrote: > >>On Mon, 18 Jan 2010 19:10:51 -0600, John Fields >><jfields(a)austininstruments.com> wrote: >> >>>On Mon, 18 Jan 2010 16:13:23 -0800, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>> >>>>We use big (75 mils in PADS) dots. There's nothing wrong with a 4-way >>>>connection if the dots are obvious. >>> >>>--- >>>If one knows what's happening at that junction, that's fine, but it's >>>happened more than once that a drafting droid saw two lines crossing and >>>figured they should be connected. >> >>When was the last time you saw a drafting droid? ;-) > >All my engineers (excepting me!) CAD their own schematics. I still >draw with pencil on vellum and let The Brat enter them for me. But I >check them very, very hard. > Are you claiming to be the last drafting droid? ;-)
From: Tim Williams on 19 Jan 2010 00:12 Busing isn't useless though. I like to draw equal signals across, like this for instance: http://webpages.charter.net/dawill/Images/RegBO.gif 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: http://webpages.charter.net/dawill/Images/Regulated%20Blocking%20Oscillator.gif This one is heavily bused: http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Triangle.gif 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: http://webpages.charter.net/dawill/tmoranwms/Elec_Induction3.gif 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" <jonk(a)infinitefactors.org> wrote in message news:ff5al512h08e7ome836c0d36efcfe3obnk(a)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
From: D Yuniskis on 19 Jan 2010 03:17
Hi John, John Fields wrote: > On Mon, 18 Jan 2010 16:13:23 -0800, John Larkin > >> We use big (75 mils in PADS) dots. There's nothing wrong with a 4-way >> connection if the dots are obvious. > > If one knows what's happening at that junction, that's fine, but it's > happened more than once that a drafting droid saw two lines crossing and > figured they should be connected. > > Resolving that ambiguity by breaking that "intersection" into two tees > disappears the problem. 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. |