PCB layout designer problems basic tips

Discussion in 'Electronics Resources' started by relicmarks, Nov 20, 2008.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    PCB layout designer rules

    1.) seperate the power grounds, signal grounds, analog grounds, digital grounds, control grounds
    2.) Keep inputs and outputs seperated and isolate to prevent oscillations
    3.) Oscillation can happen from the inverting input and non-ineverting input of op-amps, coupling between parallel signal traces
    4.) Place Capacitors that bypass supply voltages or decouple very close to the IC chip pins
    5.) Use VIAS for signal grounds
    6.) Keep power and ground track/traces running close proximity?
    7.) Need Proper terminations of unused Op amp pins or sections
    8.) Give good spacing and Clearance between tracks and pads
    9.) Put Reference designators are both on the schematic and on the PCB silkscreen to help troubleshooting
    10.) Put alot of TEST POINTs on the PCB's for each stage/section to break down into blocks to help troubleshooting
    11.) Put alot of board cut/jumpers to isolate sections & stages from the power supply, to each stage/section on the circuit to isolate them if needed to troubleshoot or seperate the power supply if blown
    12.) Put connections on the edges of the PCB's
    13.) Isolate and seperate multiple inputs and outputs VCC and Grounds
    example. if you have 7 input molex connectors and 7 output molex connector and their is a SHORT from VCC to ground it will damage every single input and output IC chips
    14.) Keep the Clock signal seperate/isolated from analog signals or amplication inputs


    What else have you guys came across that had PCB problems from layouts,design issues etc.
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
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    There have been many books written on the subject, it would be epic to try to be comprehensive about this subject on a forum!

    Favourite Books for PCB design:

    Printed Circuit Board Design Techniques for Emc Compliance : A Handbook for Designers
    EMC and the Printed Circuit Board : Design, Theory, and Layout Made Simple

    Steve
     
  3. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    steve

    are these books good and can give more information about the list i made?

    If i build a schematic on Circuit maker or electronic work bench how do i make a PCB out of the schematic drawing program?

    is it a Protel File? , Gerber file? or Netlist?

    Which one do i give to the PCB Fabrication house to print PCB's ?

    Can't the PCB fabrication house do the routing and layout for a Price?

    I just want to give them the schematic thats it

    The routing and layout is way to hard and can cause alot of problems
    but i do the schematics on these programs
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    I finally found a torch!

    [​IMG]

    :D
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Sorry Wook, this is a no flame zone.

    Note to RelicMarks, you might want to READ some of the recommendations before asking more questions. They were recommended from your 1st query. There is no substitute for research. Speaking for myself, I just jumped in there making PCBs, I did this over 30 years ago as a teenager. This too is research, I might make a mistake or two, but I'll learn from them.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    It's kind of a running joke, Bill ;)
    A couple days ago in another thread, I remarked that answering our OP's Q's
    reminded me of Herakles and the Hydra in Greek mythology - answer one question, and many more appear; cut one head off, and more appear!

    Relicmarks,
    Why would you ask Steve if he thought the books he recommended were good, when he told you when he mentioned them that they were his favorites? :rolleyes:

    If you don't want to spend money at the moment, try looking here:
    http://www.smps.us/pcb-design.html

    Can't tell you that. Circuitmaker Student doesn't have a PCB layout editor. Circuitmaker 2000 Pro had Traxmaker, but both products are discontinued; you can't get them anymore. I've been using Cadsoft's Eagle Layout Editor for schematic capture and PCB layout. Too bad I don't have the BBS Spice simulator package, or I wouldn't have to test designs using other Spice simulators first.

    You can download Cadsoft Eagle at their website. The demo version is limited to 3"x4" boards, and two layers.

    You check the PCB fab houses' FAQ.
    Check out this site for lots of info and how to avoid pitfalls:
    http://www.batchpcb.com/

    They don't design circuit boards; they make them to your specifications.

    Then hire an engineer to take the schematic and make a PCB out of it.
    Their time does not come cheaply.

    It's not that hard - only when you're new at it. Making mistakes is not always a bad thing, if you learn from your mistakes. Besides, you will wind up with lots of drink coasters for parties. :rolleyes:
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,699
    907
    @relicmarks
    Here is a good online source of design information:

    David L. Jones : PCB Design Tutorial
    http://alternatezone.com/electronics/files/PCBDesignTutorialRevA.pdf

    @SgtWookie

    Did you know a famous chemist, Louis Fieser at Harvard, invented Napalm? It is not known to this day whether the inspiration came from some overly inquisitive students or not. :D

    This is my one day to teach, so off I must go.

    John
     
  8. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Because im looking for books or turtorials that give good VS bad guide lines

    im just looking for guide lines , like my list is

    i just need good guide line list what not to do and whats good to do
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    "Because" what? To what is that answer or response? Have you looked at ay of the resources people have already provided information and or links to?

    John
     
  10. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    13.) Isolate and seperate multiple inputs and outputs VCC and Grounds
    example. if you have 7 input molex connectors and 7 output molex connector and their is a SHORT from VCC to ground it will damage every single input and output IC chips


    How can you Isolate each VCC and ground for each stage, inputs ,outputs, digital circuits, analog circuits?

    I know designers have used isolation taps on the secondary of the main transformer or use multiple power supplies to ISOLATE each VCC+ to grounds

    So if there is a short on +VCC to ground it only damages those IC chips and power supply not ALL it doesn't take them all out

    How would u guys Isolate +VCC and Ground for each stage, inputs ,outputs, digital circuits, analog circuits, without using multiple power supplys or TAPS?
    or is this the only way

    I seen a circuit where is uses one power supply but TAPS it with different zener diodes and regulators for each , inputs ,outputs, digital circuits, analog circuits

    So if you have 7 input molex connectors thats 7 +VCC and 7 grounds you have to isolate, how would you guys do this please?

    To isolate 7 +VCC from each other and isolate 7 grounds from each other how please? without using multiple power supplys or using a custom transfomer with a bunch of TAPS for different voltages?
     
  11. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Your comment is complete gibberish to me. What don't you understand about isolating Vcc and Ground?

    John
     
  12. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    is how to do it for multiple stages/sections

    Chains and chains of audio and digital stages , how to isolate each VCC and ground from each other

    if you use the SAME VCC and ground from all of them , if there is a SHORT than it will damage alot of IC chips
     
  13. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    Walter,

    People contribute on here to help you, but yet you do not awknowledge the information and it is very frustrating. When responding, it is very typical of you to use more question marks than periods. I think we are uncertain that you are taking anything in.

    I don't know what your motivations are for asking all these questions. If you are required by your employer to do these things, then perhaps they had a poor lapse in judgement by hiring an unqualified person. Or, if it is a self-motivated endeavour, then why not buy a few books and learn these things for your self?

    The key to being good in this field is the ability to source information and interpret. In order to understand what is happening, you must go back to the basics. Most of what you ask is too high level (ie. proper grounding) to be explained properly without starting from the beginning. Over the years, the most important skill I have learned is to pick up a book and teach myself the content. Another skill that I learned is to source information from the internet or library. Without these qualities, I would not be good at what I do. I suggest you seek such abilities in order to be successful. You clearly have the motivation to do this, so go for it!

    With all due respect,

    Steve
     
  14. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    sorry for all the questions im just willing to learn but need some insight and guideance also


    I just thought if i did the schematics at my house but not the routing and layouts that the PCB Fabrication house could do them

    Because alot of problems can happen from routing and layouts and i don't have the experience for that

    Thats why i didn't know which file i should give the PCB fabrication house a Protel File? , Gerber file? or Netlist? for me to bypass the process of doing the routing and layout for the schematic i drew up

    I don't want to get involved into routing or layouts , but i like to make a guidance list to help me and others to know the problems of routing and layouts

    So if you have schematic you can tell the routing/layout designer some helpful tips that you want
     
  15. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    There are individuals and companies who will do your layout and routing for a fee. But, that concept seems completely opposite the question with which you started this thread.

    So, are you asking for knowledge resources that will help you do the routing and layout, or are you asking for suggestions of places that will do it for you?

    John
     
  16. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    My workplace will do it for you, but be prepared to pay. We charge about 125K / year for an engineers time (not what I get paid unfortunately).

    Steve
     
  17. flat5

    Active Member

    Nov 13, 2008
    403
    17
    One way to isolate is to use decoupling resistors on the Vcc. Google did not help me to elaborate. Basically, feed each IC power through a series resistor and a bypass cap to ground.
     
  18. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) So, are you asking for knowledge resources that will help you do the routing and layout, or are you asking for suggestions of places that will do it for you?

    BOTH , because i want to be educated on routing and layout because of reasons like this

    Most companys i work for and still do they have so many PCB routing and layout problems , that i want have a GUIDE LINE LIST of routing and layout problems because than i can learn from them so when i make my layouts and routings to a engineer that im going to be paying him i can give him this list and say please don't do these problems or watch out for these things

    GUIDE LINE LIST of routing and layout problems this is what i need

    2.) One way to isolate is to use decoupling resistors on the Vcc. Basically, feed each IC power through a series resistor and a bypass cap to ground.

    If the capacitor gets SHORTED to ground won't this take out all the IC chips to all +VCC rails to ground?

    So i can just Tapp off "Fanning out" the B+ supply with series resistors and bypass caps to ground ?
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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    Have you read through all of the material that several of us have provided links to, or do you expect us to type it all into a neat list for you?

    If you're hiring someone else to do it, they should already know about those kinds of things.

    It's not that simple. Also, there are always compromises/tradeoffs that must be made.
    No.

    Resistors in series with the power supply will consume power. Fuses will provide a "weak link" to burn out instead of PCB traces, protecting the circuits while consuming minimal power themselves. Choose fuses to handle the maximum load that might be expected under normal operation, including surge currents when starting up/shutting down.
     
  20. sprintf

    New Member

    Nov 5, 2007
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    I think this ties into a really fundamental part of engineering. If engineering was just a matter of taking certain input specifications and running them through a set of guidelines to achieve your goal, no one would bother paying engineers what they do (and computers would probably be the engineers!). Engineering requires knowledge, experience, and critical thinking with to produce whatever your desired output.

    While you might find guidelines on a lot of topics, these are not replacements for engineers. There is no easy way around this, which is exactly why engineers can be paid so highly. If you want to acquire this knowledge you need to read the relevant texts and apply what you've learned (which may mean doing problems, designing/testing a circuit, designing/testing a PCB). Reading these forums is very helpful as well (I've learned lots from my lurking). These things can take a long time to learn and if you don't have that time, hire someone who HAS spent the time!

    I haven't made many contributions to the forums so I hope this does not appear to be too negative. I think it's a good thing to remember!
     
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