Re: EMC compliance question

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).
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?
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!]
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.