If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Right.
As Doc Conner said, schematics never look like the way the way they are routed.
Wire connection lists (or tables) as you stated are typically used in assemblies and where absolutely control and selection of wires are critical for design. For example, in industry (especially in military hardware), schematics ARE NEVER used during manufacturer. Wire connection lists are used exclusively for wiring boards, hardware, etc....
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Wow! This is VERY valuable input. Every one of you have unique and valuable insight. The conceptualization of many was exemplified in a picture of the Mazilli driver by TDU in the old tread on the subject: And I think here is where I struggle (& by some of the responses; others of you have also pondered this issue). In the schematic we see the use of right angle line WHICH DON'T SEEM TO CLARIFY! Just my opinion here but it seems like conventional habit to use these right angle "boxes". When in fact many of the techniques point to diminishing the "squares-within-squares" of wiring; choosing instead the shortest distance between two points...
I hope I'm expressing myself well enough. Here I look at a recent project & have typically started from the left as introduction of input current. You can clearly see that if I continued along this course I would have a circuit perhaps as long as my out-stretched hand but when I see the completed circuits they measure perhaps 7 cm. as in the above example.
I'm aware that this is not a particularly complex circuit but the schematic (to my mind) typify the demand for shortening those "right angle boxes".
....Just as a little aside: I've read everyone of theses posts about 4 times as they typify a different way of thinking that is so unique to each person; from my perspective so fascinating!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
wrote ... In the schematic we see the use of right angle line WHICH DON'T SEEM TO CLARIFY! Just my opinion here but it seems like conventional habit to use these right angle "boxes". When in fact many of the techniques point to diminishing the "squares-within-squares" of wiring; choosing instead the shortest distance between two points...
Well, you are quite right. Like I said before, a schematic is absolutely NOT a map specifying how the parts should be laid out in the finished circuit. All the schematic specifies is what should be connected to what. The right-angled wires are just a conventional habit (unless you're Bob Pease: ) There are other conventions too, like drawing the schematic with more positive voltages towards the top of the page, and with signal flow from left to right, that won't necessarily hold in the finished circuit either. These all make the schematic easier to read in terms of visualising how the circuit works, but don't give any hints as to how you might actually construct it.
How to lay out the parts, what kind of wires or circuit boards you need to connect them together, and so on, is a separate package of information that is just as valuable as the schematic. An experienced technician could probably make you a working circuit just from a schematic that you handed to him. But that's because he knows from experience what parts to choose and how to lay them out, not because the schematic contains all the information needed.
Another good way of learning is to find projects that have a PCB layout published as well as the schematic. Study them, or maybe even buy a couple of kits and make them.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
In digital system designs you will often see a bunch of 0.1uF capacitors seemingly tucked away in one corner of the schematic, (or even on a seperate page!) Often all connected in parallel to the same supply lines! Whilst they are all close together on the schematic for neatness, they are often scattered across the final PCB for supply decoupling purposes. In this instance the schematic may contain a written note that says something like "C12-29 to be located as close as possible to IC1-18".
As Steve C said there are many conventions. Some good - some bad. One I am personally not fond of is the modern trend to NOT show connections as lines on the schematic, but instead just show wire "stubs" with the node names at the end. Whilst this is acceptable for some things like supply rails, address and data busses, it can be incredibly frustrating trying to trace several signal lines on a paper schematic when you can't automatically search for the net names!
Registered Member #580
Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410
Oh yes, i made that mistake once, there was a schematic with 2 small capacitors connected across the supply with no indication they had anything to do with any other part, so when i built it i id exactly that. On the right hand side of the board i put all 3 capacitors LOL. unless i learned what a decoupling capacitor was and though, oh is that what they were supposed to be LOL. These should be about 10nf and placed directly across the supply pins of any ICs running at high frequencies or with square waves. This allows for rapid moments high current during the transitions that a typical filter cap is not capable of. Due to its close proximity there will be minimum inductance (which would cause ringing on the supply if it was high inductance at the moment of transition)
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
GeordieBoy wrote ...
In digital system designs you will often see a bunch of 0.1uF capacitors seemingly tucked away in one corner of the schematic, (or even on a seperate page!) Often all connected in parallel to the same supply lines! Whilst they are all close together on the schematic for neatness, they are often scattered across the final PCB for supply decoupling purposes. In this instance the schematic may contain a written note that says something like "C12-29 to be located as close as possible to IC1-18".
As Steve C said there are many conventions. Some good - some bad. One I am personally not fond of is the modern trend to NOT show connections as lines on the schematic, but instead just show wire "stubs" with the node names at the end. Whilst this is acceptable for some things like supply rails, address and data busses, it can be incredibly frustrating trying to trace several signal lines on a paper schematic when you can't automatically search for the net names!
-Richie,
Its also very bad for a pcb designer. They may see the caps all in parallel next to each other, and simply place them anywhere as opposed to right next to the Vcc of thips for proper bypassing. I've seen this happen many a time.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
When I have a low frequency / low power circuit (don't have to worry about ground layout) and plenty of room, then I do have the option to build the circuit exactly as the schemnatic is layed out, signals flowing left to right, more positive to the top. This has the great advantage that I can glance from circuit to schematic and know where I am, for debugging, for adding components.
In a circuit where ground integrity is important (like most of them), I often redraw the schematic as I intend to build the circuit. This trials component placement and ground current flow before I've started cutting wires and toasting components. Again when I'm finished, I have a schematic and a circuit that look like each other. It's a bit of an art drawing an understandable schematic in the form of a good circuit layout, but it generally can be done.
Frequently, the ground/signal integrity needs are met by having a straight line signal flow, with a straight ground underneath it. This reduces the chance of output ground current creating voltages across inputs etc without actually having to do much thinking. Power supplies and control signals can be "flown-in" from easy to organise remote locations, as long as their final decoupling capacitors are nailed to the ground next to the component that matters.
Even if the schematic shows a single wire for one of the supplies, don't be afraid to replace that with a single point for the supply, and then a small value resistor to each point that consumes it, with a local cap to ground on each point for decoupling. In some cases, current consumption means a resistor cannot be used, but it's a good default to try for. It gives you a way to organise the layout, by seperating the important signal flow stuff and its ground from the tedious housekeeping of power supply. It allows better decoupling of stages from each other (which often suffers in a first lashup) and allows you to measure current in individual stages for debugging (I keep coming back to debugging!)
One last thing is to spell out the ground issue. That 0v net called ground - on the schmetaic it is everywhere a perfect 0v. In a circuit, only a point node will be equipotential 0v, anything extended like the ground plane on a board or a bunch of wires on a breadboard will have some resistance and inductance. Just calling it ground and making it fat doesn't make it 0v. As the operating frequency rises, the inductance becomes more important. The only way to make the ground behave correctly is to realise that *all* current flows in loops, that what comes out of the +ve of the supply decoupling cap is also entering that cap from the ground terminal, but whereabouts in the ground is it flowing before that? Answer that question for each current loop, organise those loops so they don't intersect, minimise the area of each, and then you'll have a floorplan which stands a chance of working on a real resistive and inductive ground. Linear Tech have got some quite nice app notes on visualising the current flows around their switch-mode power supply converters, obviously they have had a lot of inexperienced people lay them out with inappropriate placement of decoupling components, and they've radiated and mis-behaved. Even something as apparently simple as the input filter, output filter, inductor and in-chip switches is still complicated enough to be non-obvious.
There's always a tension between the benefits of size, artistic neatness, working, looking like the schematic, which only experience will resolve.
Registered Member #538
Joined: Sun Feb 18 2007, 08:33PM
Location: Finland
Posts: 181
I usually start designing my boards PCB-layouts by drawing the different parts or "modules" of the schematic first like power supply components as their own unit, input amplifier as its own unit etc. When I've drawn all the modules as neatly/tightly as I can I start fitting the modules together to make the final layout, the last thing I usually do is to draw the Vcc lines to the different modules.
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Dr. Slack wrote ...
.....Frequently, the ground/signal integrity needs are met by having a straight line signal flow, with a straight ground underneath it. This reduces the chance of output ground current creating voltages across inputs etc without actually having to do much thinking. Power supplies and control signals can be "flown-in" from easy to organise remote locations, as long as their final decoupling capacitors are nailed to the ground next to the component that matters.
Even if the schematic shows a single wire for one of the supplies, don't be afraid to replace that with a single point for the supply, and then a small value resistor to each point that consumes it, with a local cap to ground on each point for decoupling. In some cases, current consumption means a resistor cannot be used, but it's a good default to try for. It gives you a way to organise the layout, by seperating the important signal flow stuff and its ground from the tedious housekeeping of power supply. It allows better decoupling of stages from each other (which often suffers in a first lashup) and allows you to measure current in individual stages for debugging (I keep coming back to debugging!).....
..................which only experience will resolve.
I believe you answered a question that has plagued me for a time but I'm to re-phrase it in "beginner-speak".... so that I might double check your statement.... I had thought that I could not use a ground plane design technique for a oscillating circuit...That "signal integrity needs are met by having a straight line signal flow". I am referring to the Mazilli flyback circuit: in that I have directional signal flow and cannot use a ground-plane short-cut to speed assembly. Am I correct in that? In these types of circuits I must maintain the integrity of the directional flow & my option is to simply by physically shortening the connection or working in diagonal, etc; but I can't "bunch-up" polarized connection points....(?)
Often, in examples wherein transistors are used in circuits the authors use amplifiers, etc with large collections of grounds that one could use a "ground-plane" technique for speed of assembly, etc. With those examples there are a great many options to complete the circuit, for-shorten the schematic or what not.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Conceptualizing: Moving from Schematic / Wiring Diagram; to Finished Circuit
) There are other conventions too, like drawing the schematic with more positive voltages towards the top of the page, and with signal flow from left to right, that won't necessarily hold in the finished circuit either. These all make the schematic easier to read in terms of visualising how the circuit works, but don't give any hints as to how you might actually construct it.
