Worst case design

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Hi Freaks,
How should you design a board that goes into a handheld device (say something like a GPS or cell phone) for worst case? How do you estimate the EMI, noise, signal integrity issues, etc. before you deploy your design? Is there any way you can simulate an electrically "harsh" environment? Any links or tutorials on this would be helpful.
Thanks.

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Seems to me anything I make is a worst case design

The largest known prime number: 282589933-1

It's easy to stop breaking the 10th commandment! Break the 8th instead. 

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There are some very expensive simulation tools for that sort of thing.

Leon

Leon Heller G1HSM

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And there are also some very expensive test tools that convert expensive designs that has passed expensive simulations into expensie pieces of crap. Anyway, simulation tools reduces the amount and cost of expensive crap, moving the money from crap to simulation companies.

A good PCB design book may help.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Wouldn't it be cool to have a box like a household microwave oven in which you could put your design into and "fry" it to see which is your weakest link?

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The old chattering-relay and spark gap tests have some merit for generating EMI. If you have access to a place where they are using plasma cutters - that will be as harsh as you're likely to find, but they will pretty much swamp/jam any wireless communications , especially when starting a plasma arc. Many ordinary PCs will reset and/or crash in the presence of these industrial cutters

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Yes, it would be nice, but, not very useful. I've done perhaps 50 CE EMI certifications. There is a lot you learn in that process and, if learned, helps with things like board layout. Unfortunately, I cannot catalog all this stuff, because its sort of .... "uh... see that trace that goes under that fast switching FET? You are better off if you route it somewhere else."

Further, designing something for the absolute bombproof worst case, unless you are doing a military or space project, will ultimately loose you money. You simply cannot afford to put everything in for those boards that don't need it. Here is an example: for avionics, you need to design things to withstand, and worse, not malfunction, in the presence if lightning induced current pulses. Design a GPS add-on for that level of protection? No way!

My $0.02US (which is now worth about $0.015)

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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When I worked on military communication systems our equipment had to withstand a nuclear EMP. I can't remember the E and H field strengths, but they were quite colossal. The UK MoD has a special test facility where they simulate an EMP for this sort of testing.

Many years ago I installed a TRS-80 in a factory with lots of plastic injection moulding machines. The computer worked OK, but floppy disk drives were clicking continuously due to transients from the moulding machines loading the heads.

Leon

Leon Heller G1HSM

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I believe that the point of the last two posts is that you cannot afford to make things universally bomb-proof.

What is harsh for an automobile could be quite inadequate where human-model electrostatic discharge is a problem. What is harsh for a factory, such as Leon described, could be the wrong thing for an automobile. And both could be wrong for avionics. On the other hand, not many things will withstand a 5' drop on concrete like many hand-held devices do (and many don't). There simply is no universal "bomb-proof".

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Build it on a breadboard with your 100MHz clock oscillator dangling off wires. Use no decoupling capacitors, and then try to get 10ns performance from your data bus.

If it works there, your PCB will be a breeze!
.... this I know from personal experience.

Simulator shmimulator!!!

of course, you could make a nice HERF generator using a magnetron. To make it even better than the continuous wave system used in a typical microwave oven, send in nanosecond pulses from a charged coax and use the magnetron in cold cathode mode. This can crash a computer from quite a distance if done correctly and it will not give you cataracts or RF burns.

Brad

I Like to Build Stuff : http://www.AtomicZombie.com

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The UK police are experimenting with something like that for stopping cars they are chasing.

CE includes EMC requirements for immunity to external signals, unlike FCC. They are nothing like as stringent as the military ones, of course.

Leon

Leon Heller G1HSM

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Last time I asked about EMC tests for cars, they were using something like 400V/m electric field for EMC tests. I saw many systems (like PC boards, ATX computers, etc) that crash even at 2V/m.

Similar approach would became a powerful weapon, though. Imagine if it is used against a bank or at Wall Street most famous building.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Our radio systems had to withstand 3000V/m, IIRC!

Leon

Leon Heller G1HSM

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Yep I was getting at the same thing: the ever demanding automotive market. Nowadays, they want no less than military standard and they won't even pay for it.

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That's a great idea, Leon.

It's like cell phones and water. Don't know why they haven't come up with an inexpensive common-man every day cell phone which is water resistant. (I think I have seen a few but you pay a steep price for them).

I had one that went into the washer along with the clothes and now I have to pay $200 for a new one. (I think the original phone costs about $50, it is a very basic phone). I think the PCB is good but the display is conked out. In general are PCB's water proof? How about LCD displays?

I guess I am going to use a water proof cover or something to protect my cell phone till they come up with something that is water, earth, fire, wind and vacuum proof phone.