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PCB track layout to schematic conversion

Discussion in 'Electronic Repair' started by N Cook, Mar 30, 2007.

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  1. N Cook

    N Cook Guest

    Capturing the track layout on polyester pcb - I've just tried holding
    white card laid 45 degrees to the component side and illuminating the card
    with a bright light, masking off around the board with opaque card.
    Photographing and then greyscaling and upping the contrast, loses the small
    component shadows. Giving a very usefull track layout with a bit of manual
    touching up for big component shadows etc .
    Other photos for resistor values and overall views plus manually recording
    overlay numbers that are hidden, transistor types, capacitor values etc

    Now the fun bit, it would be nice to expose, onto rubber sheet, pcb etch
    fashion. Mark node numbers and stretch into straight lines the DC rails and
    one or more other major lines and then manually cut and bridge or whatever
    for first stage schematicing.
    Anyone know of a pc application that does this stretching of a digitised
    image under human control.
    cut-down example without any manual retouching of the photo stage
    http://home.graffiti.net/diverse:graffiti.net/pcb1.jpg
    http://home.graffiti.net/diverse:graffiti.net/pcb1.jpg
    http://home.graffiti.net/diverse:graffiti.net/pcb1.jpg
     
  2. N Cook

    N Cook Guest

    revised version
    Capturing the track layout on polyester pcb , I just tried holding white
    card laid 45 degrees to the component side and illuminating with a bright
    light, masking off around the board with opaque card.
    Photographing and then greyscaling and upping the contrast, loses the small
    component shadows. Giving a very usefull track layout with a bit of manual
    touching up for big component shadows etc .
    Other photos for resistor values and overall views plus manually recording
    overlay numbers that are hidden, transistor types, capacitor values etc

    Now the fun bit, it would be nice to expose, onto rubber sheet, pcb etch
    fashion. Mark node numbers and stretch into straight lines the DC rails and
    one or more other major lines and then manually cut and bridge or whatever.
    Anyone know of a pc application that does this stretching of a digitised
    image under human control.
    cut-down example without any manual retouching of the photo stage
    http://home.graffiti.net/diverse:graffiti.net/pcb1.jpg
    http://home.graffiti.net/diverse:graffiti.net/pcb2.jpg
    http://home.graffiti.net/diverse:graffiti.net/pcb3.jpg
     
  3. I use a flat bed scanner - with a black cloth over the top to keep out the
    light. By playing with the grey scale values you can usually separate the
    tracks from the rest. The component side can be flipped and overlaid.
    Beauty of the scanner is the size can be actual and repeatable.
     
  4. N Cook

    N Cook Guest


    I've previously tried that but I could not get separation as not enough
    contrast between laquer covered tracks and polyester.
     
  5. Right. If it's any help I use an Epson GT 9500 in 24 bbs colour. Can't
    really help with the software as it's RISC OS.
     
  6. N Cook

    N Cook Guest

    Is there a general guidance for human only layout to schematic conversion
    anywhere out there? I tend to start with DC rails but then what. I imagine
    the numbering sequence for Rs and Cs should give a broad area of where to
    plonk them in the final schematic but a thin infinitely extendable rubber
    matrix would be nice.

    The other problems with using a scanner are possible scratching the document
    glass and the solder points end up white rather than black.
     
  7. Eeyore

    Eeyore Guest

    You do have some of the most curious ideas ?

    Do you want to improve a layout ?

    Creat a netlist and import it back into a pcb package. You'll have to draw the
    schematic manually though which will give you a netlist anyway.

    Graham
     
  8. I really don't know. It's one of these jobs I find enjoyable, but then
    with me it's mainly a hobby. What I do do is keep 'building blocks' of the
    common things like say an op amp component layout.
    Generally the business side of PCBs don't contain anything which will
    scratch glass.

    I only use the pic as a guide and retrace the tracks using a vector
    drawing prog. You need to have nice crisp artwork to start off the PCB
    producing process and a photo of the board complete with lacquer can't do
    this IMHO.

    But I've not used any of the clever CAD progs that are around. It's quite
    possible some short circuit a lot of the donkey work.
     
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