Netlist error in schematic.

Discussion in 'The Projects Forum' started by thebenman, Jan 26, 2014.

  1. thebenman

    Thread Starter New Member

    Jan 26, 2014
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    Hey,
    I got this schematic off a completed project by the students of the Cornell University.I basically wanted to replicate this project and add control using relays.However,when i compiled the schematic for Netlist errors using ExpressSCH,i encountered some Netlist errors.Since this is my first encounter with schematics and PCB design,i find it a bit hard to understand.Kindly help me in debugging the schematics.I have attached the schematic file.
     
  2. tracecom

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    Apr 16, 2010
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    The schematic was done by someone who apparently either (a) had no intention of making a PCB or, (b) didn't know how to use ExpressSCH properly. It contains components that are improperly constructed and/or improperly labeled. Do you intend to buy a PCB from ExpressPCB for this circuit?
     
  3. thebenman

    Thread Starter New Member

    Jan 26, 2014
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    Yes, my ultimate goal is to create a PCB from the schematic.This is the only schematic that i could find in the website.The link to the website is <a href="http://people.ece.cornell.edu/land/courses/ece4760/FinalProjects/s2011/bjh78_caj65/bjh78_caj65/">LINK</a>
     
  4. thebenman

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    Jan 26, 2014
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  5. tracecom

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    My question was whether or not you intend to order a PCB from ExpressPCB. If so, then you might want to invest the time into correcting the schematic you downloaded; if not, you would be better off redrawing the schematic into some software that exports Gerber files, which ExpressSCH does not.
     
  6. thebenman

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    Jan 26, 2014
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    Since i did not draw them myself i don't think that i would be able to do redraw in a different software.So i will be willing to order it from ExpressPCB itself as it sounds easier.Having said that,i do not quite understand those errors with the schematics.
    Will opening the schematics in one of those software that you mentioned help,incase it supports the file type
     
  7. tracecom

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    It has been a while since I used ExpressSCH, so I won't be much good at correcting errors. In addition, I wouldn't have much confidence in the resulting PCB due to the other unknown errors that the original designers might have included. My advice to you is to spend your time learning a better software package rather than correcting this drawing. DipTrace is what I use, but there are others: Kicad, Eagle, FreePCB, e.g.

    Maybe someone else here with recent ExpressSCH experience can help.

    Good luck.
     
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  8. thebenman

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    Jan 26, 2014
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    I do have to learn a better software package like you said,but i am in a tight deadline to finish this project.Thanks Anyway .
     
  9. ErnieM

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    Apr 24, 2011
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    I agree here with tracecom. I'm already familiar with several schematic capture/pcb creation programs & systems, ExpressPCB included. ExpressPCB only works within that companies system, though you can get them to send you the gerbers (basically by buying the boards twice).

    Using another program (my choice would be Kicad as it's free and unencumbered) would take more time but teach you skills applicable to every PCB program.

    Finally, if I was looking to duplicate their work I would start with a hand wired breadboard so I was free to make changes as desired.
     
  10. ErnieM

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    Apr 24, 2011
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    OK, we cross posted. ExpressPCB it is.

    On ExpressSCH's menu you can click File | Check schematic for netlist errors. Do that, do that a lot. Each time it pops u it gives much detail about the first error it found in the netlist. There are many component ID errors as the person who drew this used that field for the part value. Fix them all.

    Some (all?) components were made without pin numbers, as the nuimbers you see are lables not dissociated with the pin. To fix that cut and paste the component into a free area, ungroup it, fix the pins, then regroup it and move it back into place.
     
  11. thebenman

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    Jan 26, 2014
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    I wouldn't mind mind buying the board twice considering the spot i am in.Could you elucidate the process of PCB design .Does it always start with a schematic like this one here ?
     
  12. kubeek

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    Yes, drawing a board without a schematic is very prone to errors. If you have a tiny circuit like a 555 driving a fan, then it should be possible to do right without a prior schematic, but you need to be really careful.
    When you start with schematic, first of all the pcb tool then shows you which pins connect where, and this allows you for better placement of the components. Second thing is, that because you drew that schematic you usually have a pretty good idea what should be connected where, and you will likely spot some errors that came from the schematic when drawing the board.
     
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  13. thebenman

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    Jan 26, 2014
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    I have decided to learn and debug this schematic.However ,the second netlist error asked me to ungroup the component and then enter the correct pin number and then group the component back again.But i got hung up when trying to regroup the component back again.Could you suggest me how to regroup the component back again ?
     
  14. tracecom

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    I am afraid that you are going to spend a lot of time on this schematic and still not get what you want. According to the bill of materials for this project, the Cornell students used a PCB from the engineering lab for their projects. They did not have a PCB made, as is substantiated by the photos in the project description.

    For that reason, and because of the numerous netlist errors, I don't believe that all of the components in the schematic have associated footprints. If I am correct, even if you resolve all the netlist errors, you still won't be able to get a PCB made from the schematic without creating a footprint for each component included. Only then will you be able to arrannge all the footprints on the PCB layout; this layout will not be extremely difficult for someone with previous experience, but daunting if you are a beginner.

    If you are set on duplicating this project (with or without changes,) you would be far ahead to identify the project board used by the Cornell students, and use their schematic to build a similar control board.

    As one of the other members here says, "It's only my opinion, and I could be wrong."

    Once again, I sincerely wish you the best of luck.
     
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  15. thebenman

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    Jan 26, 2014
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    I had mailed to the person who had completed this project and he sent me the latest PCB and schematics.I had a doubt on whether these were all the boards that were used and where was the camera mounted.I am asking you this since i believe you had gone though the webpage.
     
  16. tracecom

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    Post the PCB file, and I will see if I can open it.
     
  17. thebenman

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    Jan 26, 2014
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    I am attaching all the three PCB files.
     
  18. tracecom

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    I am guessing that the original project was completed without any of the three custom PCBs. I further guess that the intention was to replace some/most of the flywires on the assembly in the photo with two of the three PCBs, but I see no evidence that was ever done. (As an aside, I don't much like the look of the PCB layouts, but they may work.)

    It seems to me that the main schematic is the best (most complete) reference document to use for the hardware design. And painful as it may be, I would follow the advice previously given by ErnieM. He does electronic design and PCB layout for a living.

     
  19. ErnieM

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    Apr 24, 2011
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    I say that because (in my experience) you don't wave a design worth spending the $$$ to make a PCB until you have a working breadboard.

    With this project I'm taking into account the "amateur" nature of the production (i.e., students in their first collaboration) and the OP's undoubtedly inquisitive nature to try to improve the damn thing into a practicable working design.
     
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