Breaking the law?

The easiest way around safety certification is to buy certified wall warts for your power source.

...Jim Thompson

You should check with the USB folks to see if there are any licensing issues with getting vendor and device IDs.

As long as you can live in the power envelope (50VA?). That's what everyone else does, though they're a PITA for customers.

....

wall wart: n. A small power-supply brick with integral male plug, designed to plug directly into a wall outlet; called a ?wart? because when installed on a power strip it tends to block up at least one more socket than it uses. These are frequently associated with modems and other small electronic devices which would become unacceptably bulky or hot if they had power supplies on board (there are other reasons as well having to do with the cost of UL certification).

Safety certification is one thing. EMI testing is another. FCC testing is a bear.

Another thought is to sell your unit as a "component". For example, as a kit or a not quite complete assembly. I see quite a lot of stuff advertised that way.

You could sell the display module and and have a link on your website to retailers of suitable power supplies. I suggest using a very common power supply value, such as 12V, so your units will work from a car battery, or a common 12V power supply. Make it easy and safe to get going.

You can have a "wiring it up" section on your website where you show pictures of a module hooked up to a power supply and a computer - and a bit of discussion.

Roger

The USB board will already have a legitimate ids, so you are covered.

Roger

The campus where I work has their own FCC open-air test site (we do self-cert), and part of my newbie orientation was to observe and assist in testing of a couple of products. The process itself is simple enough (though repetitive and a bit boring), but it's the COST - for a small-run semi-hobbyist article - that is utterly prohibitive. I think our OATS cost about $150,000 to build (not counting the actual structures that it's built on and in - that's just equipment, integration, calibration and testing).

Hello Larwin,

It doesn't have to be. Just make sure nothing can leak onto the power cable and the device itself is quiet, with a nice ground plane etc.

I found EMC cert to be pretty straightforward. Sometimes even relaxing and uplifting, for example when the site was out in the boonies with great views, wildlife, no traffic.

Regards, Joerg

It paid my mortgage for a couple of years. I had some really cool toys, a small lab of my own, off in the corner (where I decided it was quiet "enough") and all I had to do is test motherboards and processors for EMI strangeness (I found a buunch too). Ah, well, it was too good to last.

-- Keith

I'm surprised it's that little. My pre-qualification equipment was $50Kish. That was only a 6.5GHz HP EMI analyzer and a couple of antennas. Receivers were *far* more expensive and less versatile.

Hello Keith,

Why didn't it last? My impression is that EMI is becoming worse, not better. Besides the usual such as split grounds, lack of awareness and so on there are ever rising clock speeds and the proliferation of plastic enclosures. Then those nice switchers with EMI claims that are, well, a bit stretched.

The plots I receive after a blown compliance test are generally worse than those I got ten years ago. And the work to bring someone's design into compliance has become tougher.

Regards, Joerg

Hello Lewin,

That's why most companies do not own a compliance lab. You have to have good pre-compliance results and some basic gear, get the margins well below the legal limits and then head to a service provider with a 'real' EMC lab. If you pass on the first test run you can be home for $10-20k, depending on what else has to be tested.

Of course, if a company cranks out a brand new product design every couple months or so that is another matter. At the end it all boils down to how fast the lab would amortize versus the accumulating expenses for service providers.

When I am called out to a client with an EMC problem we mostly use quite basic gear and dinged-up rental antennas that had seen better times. But in all cases it passed with flying colors at the EMC site, mainly because we shot for >10dB margins on conducted and >20dB for radiated, at least for stuff above 100MHz where patterns are less predictable.

Regards, Joerg

Fabless partner sold out to other big semi company. We closed up shop, sent analyzers and antennas to the crusher , and moved on to bigger and better things.

Tougher => more demand => more $$

antennas.

I'm probably on the low side, because $150K is what we paid to refurbish it. But I think most of the crucial stuff was replaced in that refurbishing - antenna, remote antenna height/polarization servo, remote-controlled turntable for UUT, spectrum analyzer and signal generator. The only things left from the old OATS were buildings and maybe antenna cables.

assist

'real'

$10-20k,

We're a bit more complicated than just spurious emissions testing - we do a _lot_ of Part 15 devices and in a lot of cases "special" testing is required to guarantee, for example, occupied bandwidth. So we need to get down and dirty with what's being radiated; looking at the exact spectrum while the device is in different modes, checking frequency deviation for FSK devices, derating power levels for signal duty cycle, ...., ..., ...

down

At any moment there are usually about two items in the queue for the test site. I guess we probably do twenty new transmitters or transceivers per year? (just a rough guess and probably on the low side

- my team is a *very* small segment of the campus, about 5% of the total engineering manpower, and we do maybe four products a year. All our products are transceivers or receivers).

Particularly when a particular large multi-NATIONAL SEMICONDUCTOR company bought the line and then failed miserably trying to get it all working again.

One doesn't argue with Sir "Counter of Beans" under penalty of law. All capital assets must be destroyed if they're written down. Yeah, I would have made a corner in the basement for 'em, but that wasn't happening. A colleague in another site (same division) wanted my toys, but would have had to have the equivalent $$ approved by his CoBs to "buy" 'em. Since it was layoff season one didn't fight o-great-one-with-purse-strings on purpose.

Ah, Sir Counter of Beans, again. ;-)

Chances are that if it doesn't pass quickly it may never and perhaps should be scrapped. Sunk costs are sunk. Flushing good money after bad is worse than the flushing of bad money.

Hello Keith,

Yes, the famous mergers. And often you see an immense slowdown afterwards, less new stuff, longer cycles between new products and so on.

But crushing analyzers? Oh man. Why didn't you just keep them?

Well, either that or someone decides the project needs to be scrapped. Other times it just keeps dragging on.

Regards, Joerg

I read in sci.electronics.design that keith wrote (in ) about 'Breaking the law?', on Fri, 4 Feb 2005:

That's 'LORD Counter of Beans', and don't you forget it!

So don't write them down! Sell them as used equipment. Even getting 10% means MORE MONEY, which makes the noble Lord happier.