Re: EMC compliance question

On 10-10-2024 23:11, john larkin 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.
 

If your product can power usage is larger than 15W, then you get close to nothing by using external SELV supply, because then a lot of the demands on safety are back in play

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.
 

>
Lastly, it's just "good engineering" -- and great experience -- to
go through the process so you know what to *avoid* in your
future designs.  (ditto for safety requirements)
>
Increasingly, I am seeing extra scrutiny on devices that CAN "talk"
to ensure they aren't talking to anyone that they can't *justify*.
"Why are you phoning home?"  "Why are you initiating HTTP requests?"
"Why are you trying to resolve some oddball domain name?"
>
[These, of course, are a lot harder to "guarantee" without (and
even *despite*!) releasing full sources.  Especially for OTS/FOSS
OSs that may have been preconfigured (for your convenience) to
support services having communications requirements that you
of which you may be ignorant!]

 Software certs on top of hardware certs?
 

>
Assume your customer is going to need/want to certify his
use of your device and give him a leg up in that process,
pre-sale.

 For a small company making a modest number of some test instrument,
full certs will multiply development cost. That may be why I don't see
a lot of small instrument companies in europe.
 The guys I was working with in Oxford laughed at me when I asked if
our atom probe system would need to be CE tested. "CE means Cant
Enforce."
 

Some just takes the risks. If you are caught it can be an expensive risk. On the other hand, I have never heard of a case where the company went bankrupt. Have heard of large fines, but nothing that killed the company