Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Klaus Vestergaard Kragelund Newsgroups: sci.electronics.design Subject: Re: EMC compliance question Date: Fri, 11 Oct 2024 20:59:09 +0200 Organization: A noiseless patient Spider Lines: 101 Message-ID: References: <67070ba9$1$1783$882e4bbb@reader.netnews.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Fri, 11 Oct 2024 20:59:09 +0200 (CEST) Injection-Info: dont-email.me; posting-host="2e6cea8fca40ccaaa2808f365cfc2bbd"; logging-data="3968384"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18x3poh8DozzsBhwq7kbkPb0MbpruF8mxw=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:PXxfN5b+UdvVLpRRdW1H1o86BmI= Content-Language: en-US In-Reply-To: Bytes: 5551 On 10-10-2024 23:11, john larkin wrote: > On Thu, 10 Oct 2024 13:41:07 -0700, Don Y > 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