Re: EMC compliance question

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