Bashing chinese AC/DC power supplies - Page 1
Forum section: electronics / projects

author: uski
author_rank: Frequent Contributor
timestamp: December 29, 2016, 02:44:29 am
content: Hi,I have some connections in China and some sellers send me some of their products for free so I can review them.Most of the time, the products are OK but regularly I come across products which should not be sold as-is.One of the problems I regularly see is lack of proper safety testing and marking. I live in Canada, and by law all AC-powered stuff must be tested by one recognized agency (ULc, ETL, ...). I think it's the same for the USA (UL).I always report my findings to the sellers and some give no f***, but others are simply being misled by their suppliers and are really trying to understand what the problem is.When talking with these suppliers, I like to give them examples of what the issues are with their designs.But the problem is that I don't have access to the standards so I can't tell them exactly what they're doing wrong (beside "I think that's not right"). So sometimes they start thinking I'm not informed properly (because their suppliers keep telling them everything is OK).So... does anyone know any freely available document that lists some of the basics of what AC powered products should have ?For instance, sometimes there are PowerPoint presentations from schools that give some excerpts from the standards.Example questions :Is a fuse required or can they use a resistor as a fuse ?What is the minimum distance between low-voltage and high-voltage traces ? And between the high-voltage traces themselves ?PS: I tried reporting some products (which are being sold on Amazon... !) to the local authorities but they don't care. It blows my mind that Amazon sells stuff that shouldn't be sold, a lot of less knowledgeable buyers are being misled into buying products they shouldn't be able to buy in the first place. Also tried putting up very negative reviews on Amazon on the affected products, but nobody at Amazon takes a look it seems. Duh.Thanks !

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: December 29, 2016, 04:21:01 am
content: Thats what we love about these products. No rules, no standards, they just work.LBJ coined the term nervious Nelly's.

author: sleemanj
author_rank: Super Contributor
timestamp: December 29, 2016, 05:11:23 am
content: This is something that irritates me, standards to which your products have to adhere are simply not usually freely available. To me that is completely crazy, standards which are effectively mandated by authorities should be freely available from said authorities, at least one canonical standard, for everybody to be able to read, and examine the products that they are selling, and indeed the products they are buying if they wish to do so, not to issue the compliance documentation, but to verify for their own eyes the compliance (or precompliance). Imagine if you couldn't read the laws of your country without paying for a copy.Anyway, as for Chinese DC power supplies (wall warts), what you should do is simply tell the vendor that you want to see the compliance certificates for the product listing what standards it has been tested against, what is the UL listing number or whatever is appropriate for your neck of the woods. Almost certainly they won't produce one, in which case, end of story unless you are the one who wants to put it through compliance. If they do, probably it will be genuine, but if you open the product up and it looks fishy, then you can consult with the compliance outfit that issued the certificate to verify it and kick it up to them to deal with people forging their name on certificates.

author: KhronX
author_rank: Frequent Contributor
timestamp: December 29, 2016, 02:07:36 pm
content: For what it's worth:http://www.silabs.com/Support%20Documents/TechnicalDocs/AN583.pdfhttp://www.ptr.eu/en/know-how/terminal-blocks/approvals-regulations/clearance-and-creepage-distances/(links on the left side)http://www.wecogroup.com/_en/themen/techdat/techdat_kriech.htmhttp://www.frontdoor.biz/HowToPCB/HowToPCB-extra/CreepageandClearance.pdfQuote from: uski on December 29, 2016, 02:44:29 am