Protection against copying of a circuit design

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

D from BC

martin

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 about, 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, and 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" on the subject, and earnestly try to find out if somebody has had the same idea and if anything exists in the "public domain" ( i.e. written down ANYWHERE where it can be found) before you go to any more trouble.

Good luck on your efforts,

Andy in Eureka, Texas W4OAH

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

...Jim Thompson

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

Jim

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.

That only adds a few seconds of delay.

On May 28, 9:12 am, AndyS wrote: [....]

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 sees.

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

Can *you* make one oscillate without using an inductor or stupidly long wires?

Best regards, Spehro Pefhany

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! Rich

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.

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 stuff.

You can also move a trace layer inside the PCB and have the ground layer on the outside.

Sound aside, can you demonstrate it with 3' wires?

Best regards, Spehro Pefhany

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.

snipped-for-privacy@gmail.com wrote in news:1180366721.842003.184850 @w5g2000hsg.googlegroups.com:

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

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----= East and West-Coast Server Farms - Total Privacy via Encryption =----

In the US, the invention would need to be "novel", "non-obvious" and "useful". 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 ignition.... Even though both situations can be compromised by someone determined enough.

-mpm

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.

Absolutely; do not make it in the first place!