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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: EMC compliance question
Date: Sun, 13 Oct 2024 12:29:17 +1100
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On 13/10/2024 2:22 am, john larkin wrote:
> On Sat, 12 Oct 2024 11:38:30 +0200, Klaus Vestergaard Kragelund
> <klauskvik@hotmail.com> wrote:
> 
>> On 12-10-2024 01:31, legg wrote:
>>> On Thu, 10 Oct 2024 14:11:35 -0700, john larkin <jl@glen--canyon.com>
>>> wrote:
>>>
>>>> On Thu, 10 Oct 2024 13:41:07 -0700, Don Y
>>>> <blockedofcourse@foo.invalid> wrote:
>>>>
>>>>> On 10/9/2024 4:03 PM, bitrex wrote:
>>>>>> What's the deal with the "CPU board" exemption?
>>>>>>
>>>>>> "CPU board. A circuit board that contains a microprocessor, or frequency
>>>>>> determining circuitry for the microprocessor, the primary function of which is
>>>>>> to execute user-provided programming, but not including:
>>>>>> A circuit board that contains only a microprocessor intended to operate under
>>>>>> the primary control or instruction of a microprocessor external to such a
>>>>>> circuit board; or
>>>>>> A circuit board that is a dedicated controller for a storage or input/output
>>>>>> device."
>>>>>>
>>>>>> So if one sells a board that has say a PIC on it and some support logic, and
>>>>>> the 9kHz+ signals are all internal to the uP (self-clock), but it's otherwise a
>>>>>> functionally complete design other than it's not in a housing, is that an
>>>>>> exempt product?
>>>>>
>>>>> Who is your customer?  If you are selling it as a *product*,
>>>>> it is not a *compliant* product so your customer inherits
>>>>> no certifications (because there are none).
>>>>>
>>>>> If your customer integrates it into *his* product, then
>>>>> the responsibility for "product certification" falls on him
>>>>> (so, you have saved *yourself* a few pennies on the certification
>>>>> process and left him with any "problems" that your board may
>>>>> pose to *his* certification).
>>>>
>>>> A few pennies for a certified test lab to do full certs?
>>>>
>>>>>
>>>>> If you are selling to hobbyists, you *may* be able to get by
>>>>> as a noncompliant product (the first case, above) -- so long
>>>>> as none of your (few?) customers finds themselves drawing
>>>>> the ire of neighbors, etc. when your device interferes with
>>>>> their pursuit of life, liberty and happiness.
>>>>>
>>>>> But, you are still exposed as the seller of that noncompliant
>>>>> product.  How likely will your customers "have your back"
>>>>> if things get sticky?
>>>>>
>>>>> In the latter case, your customer (integrator) will *likely*
>>>>> be thankful for any steps you have taken to certify your
>>>>> "component" as he goes about looking for certification on
>>>>> *his* composite system.
>>>>>
>>>>> Why do you think so many products are sold with El Cheapo,
>>>>> off-brand wall warts instead of taking the power supply
>>>>> design *into* the overall product?
>>>>
>>>> A wart relieves one of all the AC-line safety certifications. There
>>>> are some big warts these days, including 48v ones.
>>>>
>>>> One can resell a cheap wart with the usual molded-in (usually fake)
>>>> UN/CE/CSA markings, or let the customer buy their own wart.
>>>>
>>>
>>> A wart used in an EMC certification becomes part of it. Hence
>>> mrfs listing and retailing part numbers for suitable use.
>>>
>>> Warts can be (and are) listed independently, to reduce
>>> potential testing and deployment gliches. A listed
>>> wart doesn't guarantee radiated compliance, only facilitates
>>> conducted performance on that one, main, port.
>>
>> All of the EMC tests still needs to be done even if you use a wart.
>> But LVD (safety) becomes a lot easier, if it's below 15W consumption (no
>> glow-wire test etc)
>>
>> Somebody was talking about 48V warts. Some standards only allow 24V (for
>> wet environments), and 32V for certain parts of the world
> 
> 
> 48 is super common now. All our phones are PoE powered, which is
> typically about 54 volts. Digikey sells warts up to 65.
> 
> The phones are cool. I can take one to Hawaii and plug it in and it
> works just like it does here.
> 
> I imagine that Europe has tens, maybe hundreds of millions of PoE
> devices with the Chinese version of the CE mark molded into the case.
> 
> So if European manufacturers really have to do all the CE certs and
> testing, they have one more reason that they can't compete with
> imports.

Certification costs are trivial for mass market products. China has two 
advantages over Europe - the real one is that it pays it's workers less, 
and the other is that it notionally has a even bigger internal market - 
and the rule of thumb is that manufacturing at ten times the volume lets 
you halve the price. The European internal market is about 500 million 
people, and because Europeans are better paid than Chinese it would 
probably be effectively bigger if the Chinese played fair - which they 
don't.

China does seem to go in for predatory marketing, where they subsidise a 
product for long enough to bankrupt foreign competition. Selective 
tariffs are an effective weapon against this tactic, but they do have to 
be used selectively, which Trump couldn't manage.

-- 
Bill Sloman, Sydney