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Protection against copying of a circuit design

Discussion in 'Electronic Design' started by [email protected], May 28, 2007.

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  1. Guest


    It might seem a bit dumb, what are the ways to protect a circuit from
    being copied by others?
    In both low quantity and industrial scale.

    Answers are appreciated.

  2. D from BC

    D from BC Guest

    Currently I'm using a Dremel tool to remove part numbers.

    D from BC
  3. On 28 May 2007 08:38:41 -0700, in

  4. AndyS

    AndyS Guest

    Andy comments:

    Practically impossible to prevent copying a circuit design UNLESS
    you are able to prove that nothing like it has ever existed in the
    public domain.

    For many years, I was on the "patent review committee" for one of
    the planet's largest electronics corporations, and we got dozens of
    patent applications every week for some new "thingy or other". Well
    over 90% were simply "inventions" submitted by engineers, in good
    faith, who were unaware that their idea had already been written
    published, or patented in some publication that they weren't aware of.
    In such a case, we wouldn't spend the time or money for the company
    trying to get a patent that couldn't be defended....

    That isn't a bad reflection on the brilliance of the engineer....
    only an
    acknowledgement that there are a LOT of brilliant engineers out there,
    somebody else did it first, and published it...

    Being said, if you really really really think you have done
    something that
    hasn't been done before, search the patent archives, and do a "google"
    the subject, and earnestly try to find out if somebody has had the
    idea and if anything exists in the "public domain" ( i.e. written down
    where it can be found) before you go to any more trouble.

    Good luck on your efforts,

    Andy in Eureka, Texas W4OAH
  5. Jim Thompson

    Jim Thompson Guest

    I've personally used an electric eraser with ink-type insert.

    ...Jim Thompson
  6. You can use black soldermask on your boards. If they attempt to dissolve it
    off, whatever they use on the enamel soldermask will generally eat the epoxy
    IC package, resistor color codes, capacitor markings, etc. as well.

    If your circuit can stand the leakage, there are a few opaque encapsulants
    (mostly in the aircraft industry) that will rip the board apart rather than
    let you see inside. Go to the FAA's website and look up Advisory Circular
    65-9. There are half a dozen different compounds listed under "sealant".

  7. Fred Bartoli

    Fred Bartoli Guest

    D from BC a écrit :
    I've seen that done (one customer).
    He was so paranoid about copying that he erased the part numbers *in depth*.
    Then absolutely nobody one could reverse the board, whatever the effort:
    on some parts the chips internal bonding has been erased in the process too.
  8. MooseFET

    MooseFET Guest

    That only adds a few seconds of delay.
  9. MooseFET

    MooseFET Guest

    That is not really true. You can patent the use of a circuit in some
    strange new way. Every one knows that the LM78XX regulators will
    oscillate. If you used this fact to clock your micro, you could
    patent that. You can also get a design patent on parts that the user
  10. Selling the product at a competitive price and providing good service
    are one good way-- it reduces the incentive.

    You can try removing part numbers and so on, but it won't slow down
    anyone competent by much. If there is locked firmware that is
    non-trivial, that might slow some opponents down a bit, although there
    are ways to break most protection schemes given a bit of money.
    Putting easter eggs in the firmware can help detect that. Don't spend
    too much time on any of this, IMHO.

    Best regards,
    Spehro Pefhany
  11. Can *you* make one oscillate without using an inductor or stupidly
    long wires?

    Best regards,
    Spehro Pefhany
  12. Rich Grise

    Rich Grise Guest

    Make them so quickly that you saturate the market before anybody gets
    around to copying them, and so cheap that it's not worth it for them to
    do so.

    Good Luck!
  13. MooseFET

    MooseFET Guest

    Yes, I can use cleverly long wires. If the goal is oscillation, a
    shorted tuned stub of twinlead about 3 feet long sounds about right.
  14. MooseFET

    MooseFET Guest

    Just use left hand screws to hold the cover on. :)

    I have had dealings with a company that coated their PCBs with the
    black stuff to prevent people from figuring out their design. The
    coating seriously degraded performance. I suspect they used the wrong

    You can also move a trace layer inside the PCB and have the ground
    layer on the outside.
  15. Sound aside, can you demonstrate it with 3' wires?

    Best regards,
    Spehro Pefhany
  16. MooseFET

    MooseFET Guest

    I'll have to try it out to make sure but that is likely to be enough.
    The LM78XX series has a bandwidth of something like 50MHz. This wide
    bandwidth is part of why they have such a low output impedance. 0.02
    Ohm output impedance means that it doesn't take much input impedance
    to get a gain over unity.
  17. me

    me Guest

    wrote in

    never produce it and leave no schematic copies in existance...
  18. mpm

    mpm Guest

    In the US, the invention would need to be "novel", "non-obvious" and
    I believe the LM78XX example would fail on all three counts.(?)

    However, your point is well taken.
    I agree with Spehro however. Be first to market, and be the best.

    That said, obviously don't make it easy.
    Not setting lock bits in a micro is like leaving your keys in the
    Even though both situations can be compromised by someone determined

  19. krw

    krw Guest

    Not if were a design patent. They're next to useless for such
    things, but that's not the issue here.
    ....and keep running.
    Just make sure you don't make it harder on your customer (or
    yourself) than the perp.
  20. Robert Baer

    Robert Baer Guest

    Absolutely; do not make it in the first place!
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