Recreate a PCB with a Scanner and Inkscape

turnsig

[John] has managed to replace a broken turn signal PCB by scanning it and converting to Gerber format. [John] purchased a Triumph Spitfire with toggle switch wired up for turn signal control. The “official” replacement part worked better than the toggle switch, but it didn’t cancel after turning. He was able to get the original switch, only to find it had a hole completely burned through the phenolic board. This isn’t completely surprising, as Triumph used a Lucas Industries electrical system. As anyone who has owned a car with a Lucas “prince of darkness” electrical system will tell you, Lucas systems were not known for quality. A quick Google search brings up plenty of pages attesting to this.

Phenolic resin/paper was a common early PCB material.  The FR-4 fiberglass boards most commonly used today could be considered descendants of FR-1 and FR-2 phenolic. (The FR in this case stands for Fiber Reinforced). The standardization worked in [John's] favor, as his burned board was 31 mils thick, which is still a standard PCB thickness. Re-creating an odd sized board such as this isn’t a hard job. It would however mean spending quite a bit of time with a ruler and a caliper. Rather than spend all that time measuring and re-drawing, [John] scanned his PCB on a flatbed scanner. He used graph paper as a background to verify the image wasn’t being stretched or skewed.

[John] brought his scan into inkscape, and traced both the outline and copper areas. The outline and copper had to be exported as two separate files, so he added corner marks outside the board outline as fiducials.  He then used pstoedit to convert inkscape’s eps output files to gEDA pcb format. The two files were rejoined in gEDA. From there [John] exported a Gerber, and ran it on his home PCB milling machine.  The results look good. [John] plans to make another revision of the board from a professional PCB house with vias to hold the copper to the substrate.

Comments

  1. Dax says:

    Many times when I’ve needed a breakout board for some chip, I’ve simply googled it, took the picture of the printed board and scaled it to the right size in photoshop, then printed the board by toner transfer.

  2. XOIIO says:
  3. Adobe/Flash hater says:

    Pre-coffee comment, So forgive me if I missed relevant info.
    Looks like the original board has more
    of an “inlayed” sort of copper. i.e. a heavier gauge than a typical PCB.
    I assume the copper paths are
    for sliding contact with a wiper
    type contact.
    If so, the foil on the board
    may not hold up very well
    mechanically.
    Well smoothed surfaces of the wipers,
    an appropriate lube
    (any suggestions here?)
    and using as low of a current
    (transistorized hack ?)
    through it to drive a larger
    device are just my first thoughts.

    Did like the scanning and verifying
    idea .

    ..next 3D printer project anyone?

    • kommune78 says:

      Your comment it is,
      like a poem.
      Tense and broken
      the lines flow.
      Intricate.
      Well smoothed lyrics,
      an appropriate lube.

    • Adobe/Flash hater says:

      For what it’s worth I’ll throw out a partial background on why my missives
      are such a mess.
      Firstly “Monocular Diplopia”.

      http://www.rightdiagnosis.com/symptom/monocular-diplopia.htm

      I have a horizontal ghosting
      i.e. double vision (per eye)
      very much like the ghosting we had
      with analog broadcast TV reception
      when using those old set top
      “rabbit ears” antennas.

      Because of that I have to override the web page choices of font type and size as the original choices are often
      a size that causes the letters
      to appear as roughly half overlapped.
      It’s really difficult to try to read
      when things look that way.
      thus the decision to alter the page
      into a larger & and more legible
      style of fonts.
      and yes, it can and does often
      play hell with the page layouts.
      As may be self evident,
      data and comment boxes
      are generally the worst snags for me.
      It’s also how I came by my dislike
      of Flash.
      The stuff is just fatiguing to watch
      due to my visual glitch.

      As far as My “Shatnerism” manner
      of attempted communications?
      Well hell, that’s just my ADD for ya !

      Having said all that,
      well I do do recall posting
      that I like the light handed
      style of moderation here
      and allowing anyone even trolls
      to get in a
      good zinger comment.

      So carry on as before, good people!!

  4. lis0r says:
  5. Serge says:

    I would also be interested to read about his home cnc router setup.

    • John says:

      It’s nothing fancy: a Sherline with Linistep drivers, running EMC2. I’m converting over to a chopper-based driver right now because the linisteps are really smooth but run very hot with big steppers. The 10k rpm drivetrain add-on seriously helped in engraving copper: totally worth it.

  6. ka1axy says:

    FR = Flame Resistant (not Fiber Reinforced).

    Phenolic board is far cheaper to make than glass-epoxy, but it’s much less rugged and ages poorly, which is why it is a perfect choice for Lucas. Nice hack.

    I once repaired the electronic tach (Smith’s) in a friend’s MG. The chip was a TI part, with markings, so I called up my TI rep, who looked it up and said “it’s a custom”…even though TI made a nice tach chip, Smith’s had decided they needed a custom one. He found me one in the engineer’s des drawer & sent it to me, making my friend very happy not to have had to spend $800 or so on a new tach.

    • David says:

      Good ending to that story. I think I’d have tried to get the innards from an older electro-mechanical instrument and ditch the electronic stuff. I suppose that particular MG was built after the mid-70s? Your observation about materials that Lucas used is a good example of the problems. Often Lucas and other British components were very cleverly designed. Implementation was a different story, however. A new turn signal lever from a 60s Spitfire had an excellent feel that nothing outside of Britain could match. For a few months. Apparently us yanks weren’t expected to use them so often as to wear them out.

  7. syntroniks says:

    Flame retardant sounds much better to me. I have never heard it being explained as fiber reinforced.

  8. blodgar says:

    He could use Cu-plating to reinforce the depth of the Cu.

    • ka1axy says:

      It’s probably going to get a lot of wear, so that wouldn’t be a bad idea.
      Alternatively, (though it’s a bit late for this) he could have used 2 oz. copper PCB material

    • John says:

      I’m having the final done in 2oz copper, and I’m also getting three of them so if one dies, oh well. They’re surprisingly easy to replace compared to most automotive electronics I’ve dealt with. I think the wiper will probably wear out before the first board does, though.

  9. F says:

    Even the swedes were not immune to the Lucas disease, old Saabs had “Made In England” Lucas-Girling brake calipers with poor seals. You’d be lucky to get two winters out of a pair before the salt chewed up the seals resulting in siezed brakes and another expensive trip to the mechanic.

  10. pidge says:

    Lucas switches had three positions – off, dim and flicker. Or smolder, smoke and ignite http://www.kitcar.com/articles-kitcar/humordept/lucas-prince.html (but note that Lucas torpedoes don’t sink, they fly http://www.subgenius.com/subg-digest/v4/0175.html)

  11. Jake says:

    I had few ps and pdf files around submitted to us by customers (Were pcb fab house and we can’t really handle arbituary filetypes and accept mostly Gerber files or CAM formats) and I tried with few of them to convert them gerber. Managed to export pcb files from gsview vector export function, but gEDA imports them empty. So I guess I can’t use this method after all to convert vector formats to gerber.

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