Interview with Electronic Engineer  - Page 1
Forum section: electronics / general

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 04:44:58 pm
content: My business partner and I were interviewing an EE guy recently (claims to have 25 years experience), and in the interview, we were discussing a potential project for a new type of security camera, powered by POE (power over ethernet). The candidate indicated that such a device would require CSA / UL certification. I did not think it would, since it not mains powered, and there is no shock hazard from the low voltage / low current in the ethernet cable. My partner wasn't sure, so I thought I get some input from the folks here. Did the candidate get the answer correct? Note, we are talking about CSA / UL , not radio interference testing, which is a different issue.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 28, 2013, 04:53:17 pm
content: Depends where you're going to sell it. UL and CSA marks are universally respected, but don't have much (if any) legal standing outside the US and Canada - and even then, I believe the situation varies from one state to another. The corresponding EU directives, which require a CE mark on units sold in Europe, refer to standards which are often very similar (though not identical).Safety testing covers more than just mains electric shock, though. Products are tested to ensure they don't generate high temperatures that could burn, that they don't have dangerous unguarded moving parts, or sharp edges, or dangerous voltages generated internally that could be touched by an operator. Having no mains voltages will certainly make testing easier and cheaper, but it's still necessary.

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 05:00:57 pm
content: I agree with you regarding temperature and other safety issues, but we were more looking at the power supply issues. I should have added that none of our existing Axis cameras have CSA, UL, or CE either, nor do any of the small desktop ethernet switches and routers that use wall warts for power (the wall warts themselves have UL and CSA). The bigger switches that use mains power, and have internal power supplies, all have CSA and UL.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: October 28, 2013, 05:08:18 pm
content: Quote from: Danara on October 28, 2013, 04:44:58 pmSo did you ask a question which you are not sure about the answer.Then you shouldn't ask the question on the first place.David.

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 06:27:01 pm
content: Quote from: DavidDLC on October 28, 2013, 05:08:18 pmWe didn't actually pose that question - the candidate brought it up. I'm looking for some advice on whether or not he is correct.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 28, 2013, 06:45:59 pm
content: Well... the answer is 'yes', if that certification is a requirement in the territory into which you plan to sell the product.If you're selling into Europe, then no, you don't need UL / CSA. You need to CE mark instead.I'm not quite so sure about the USA... last time I checked, I think the rules were pretty much 'sell what you like, but prepare to be sued if someone gets hurt', in which case getting your product tested and insured by UL is a very good idea even if not a strict legal requirement.The fact that your product isn't mains powered certainly does NOT affect whether or not you need the certification, though. A bear trap isn't mains powered, but it's not "safe" either.

author: Neilm
author_rank: Super Contributor
timestamp: October 28, 2013, 06:59:44 pm
content: Quote from: Danara on October 28, 2013, 05:00:57 pmIf selling into Europe, it needs to be marked with the CE mark - the UL / CSA marks are (pretty much) irrelevant. The CE mark will also cover EMC requirements and the like. Also, I believe that UL only covers electrical safety, and you might find that the requirements for CE marking also include mechanical testd

author: Kjelt
author_rank: Super Contributor
timestamp: October 28, 2013, 07:12:29 pm
content: a quick Google:http://www.ul.com/global/eng/pages/corporate/contactus/faq/general/background/Quote

author: Smokey
author_rank: Super Contributor
timestamp: October 28, 2013, 07:13:36 pm
content: It all depends on what your customers need. I'd give the interviewee extra credit for being aware of stuff like that since it's one of those things it's easy for an engineer to ignore since it might not effect the way the product works but it certainly can effect the companies ability to actually sell the damn thing once it's done.Even if your immediate customers don't require certification, it's still a good idea to find out what the tests are and make sure you design to pass them anyway so when some customer requires it you don't have to do a redesign. This is where it gets confusing though since unless you know someone who is an expert at interpreting the certification requirements they are really hard to interpret on your own. Think reading hundreds and hundreds of pages across multiple documents and you still have to figure out what applies to your product and what doesn't. It's a mess, and unfortunately a mess you have to get right or you might not be able to sell your stuff into certain markets.

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 08:23:29 pm
content: Quote from: AndyC_772 on October 28, 2013, 06:45:59 pmWe actually aren't selling them at all - they will be used internally within the company for a specialized application. Not sure if that makes a difference or not.

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 08:29:03 pm
content: Quote from: Smokey on October 28, 2013, 07:13:36 pmI agree that it is a complicated area. There are many standards, and it is difficult to determine which tests need to be applied. Since this device will be only used internally and not sold as a product, it may be possible that the test requirement threshold would be lower, but it is hard to even get that answer from the standards documents.

author: Danara
author_rank: Newbie
timestamp: October 28, 2013, 08:34:22 pm
content: Quote from: Kjelt on October 28, 2013, 07:12:29 pmThanks. That link was very useful, and your description really helped. Since this device isn't going to be sold - it is for use internally only - I'm leaning toward not thinking that it would be worthwhile to get certified. None of the commercial versions of this product carry UL or CSA (or CE), so I'm thinking that a custom version used internally is probably not going to need it either. If we ever did decide to market it in the future, we could always revisit the decision then.

author: Kjelt
author_rank: Super Contributor
timestamp: October 28, 2013, 09:03:12 pm
content: If you are not planning to sell it I don,t see the need for a certification unless you want a third party assurance about some specification the product should meet.I think the UL is familiar with such companies as the european TUV and KemaKeur. Here in europe these companies will certify products so they "officially" meet some standards such as for instance waterproofness like the IP standard or the mains safety or EMC compliancy. These certifications help backup the claims that the product complies. These companies also have huge very expensive testgear most companies don,t have, when i visited once they were testing Lotus sport cars for EMC compliancy. For an internal product I would not bother.

author: EEVblog
author_rank: Unknown
timestamp: October 28, 2013, 09:41:28 pm
content: Quote from: Danara on October 28, 2013, 08:23:29 pmIn that case it's almost certainly no. Unless that's a way you choose to self impose your own internal standards.

author: Unknown
author_rank: Unknown
timestamp: October 28, 2013, 11:32:43 pm
content: The lack of UL (or equivalent) approval might be an issue if you ever need to file a insurance claim where said device might be a suspect.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2013, 12:06:27 am
content: Quote from: Danara on October 28, 2013, 04:44:58 pmI designed a similar device for one of my customers. Because it can be mounted outside it needed to go through surge testing to get a CE approval certificate. Even if you use the device inside another device you may need to have the whole system certified. The hardest part of getting something certified is finding a 'certification company' which thinks along your wallet and not theirs.

author: tan98010
author_rank: Contributor
timestamp: October 29, 2013, 12:22:06 am
content: http://en.wikipedia.org/wiki/UL_(safety_organization)UL 1492, Audio/Video Products and AccessoriesUL 6500, Audio/Video and Musical Instrument Apparatuses for Household, Commercial and Similar General UsesUL 60065, Audio, Video and Similar Electronic Apparatuses: Safety RequirementsUL 60950, Information Technology EquipmentUL 60950-1, Information Technology Equipment - Safety, Part 1: General RequirementsUL 60950-21, Information Technology Equipment - Safety, Part 21: Remote Power FeedingUL 60950-22, Information Technology Equipment - Safety, Part 22: Equipment to be Installed OutdoorsUL 60950-23, Information Technology Equipment - Safety, Part 23: Large Data Storage Equipment

author: dfmischler
author_rank: Frequent Contributor
timestamp: October 29, 2013, 01:56:32 am
content: Years ago I worked for a company that build factory floor automation products and we needed UL approval to meet the local municipal safety codes for a plant in El Segundo. The UL people required a few product changes before accepting the products. I have no idea of the total cost impact. I remember that there were rooms in that plant that needed 1/2 hour notice before allowing people without need to know to enter, even with security clearances and escorts.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: October 29, 2013, 02:04:10 am
content: I remember 2 occasions when POE caused fire - once, around year 2002 in a hotel's server room where someone installed wireless router that created lot of smoke but damage was only the router itself plus scared hotel stuff and mad manager. Second time also wireless router, but this time sprinkler system got deployed causing altogether around $46K of damage probably covered by insurance. I don't know anything about POE, but fire dept guy was very familiar with it and when I expressed my doubts he immediately stated that it is 30 something volts and it was not his first case investigating it.

author: nctnico
author_rank: Super Contributor
timestamp: October 29, 2013, 02:16:39 am
content: The voltage supplied by PoE is supposed to be 48V but in the telecom world the actual voltage is usually close to 60V to compensate for long wires.

author: Danara
author_rank: Newbie
timestamp: October 29, 2013, 02:09:04 pm
content: Quote from: Alexei.Polkhanov on October 29, 2013, 02:04:10 amI don't think it is the voltage that is the issue. Analog phone lines have around 50vdc, and ring at 90+ vac, which can give you a zap if you are touching the wires when the phone starts to ring, but there aren't many fires started by phone lines. I think the fire hazard is due to high current causing excessive heat build up in the cables, due to the small size of the conductors, and the insulation.I think POE is quite safe as long as you install it correctly, which mostly has to do with how the cabling is done. STP instead of UTP makes a big difference, for example. High power POE is best done with a mid-span POE injector as close to the device as possible. Also don't bundle multiple POE cables tightly together -- like you might be tempted to when entering a large rack. The problems seem to be when a cable in the center of the bundle overheats because there is nowhere for the heat to go. There is an IEEE article about this issue.http://www.ieee802.org/3/poep_study/public/sep05/walling_1_0905.pdfIEEE 802.3af PoE standard provides up to 15.4 W of DC power minimum 44 V DC and 350 mA.IEEE 802.3at PoE known as PoE+ or PoE plus, provides up to 25.5 WSome vendors supply up to 50 watts for some equipment using all 4 pairs, but this isn't allowed in the PoE+ spec.My device is only drawing 3-5 watts nominal and 7-8 watts peak, so the current draw over POE is at the lower end of the 802.3af standard.