Apparently relays need to breath - Page 1
Forum section: electronics / projects

author: Poe
author_rank: Frequent Contributor
timestamp: November 22, 2022, 03:26:22 pm
content: Just something I found interesting and kind of a public service announcement since I've never seen anyone do this.Our customer had some spectacular failures. Root-cause traced to "vent nibs" not being removed. Apparently those little bits of plastic at the top of 'washable' relays are not gate marks. They're called 'vent nibs' and should be opened after soldering.https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C9136_Venting_Sealed_Relays_AppNote&DocType=CS&DocLang=ENOnly applies to energetic circuits.

author: mikerj
author_rank: Super Contributor
timestamp: November 22, 2022, 03:36:59 pm
content: Very interesting, not something I had ever considered.

author: wraper
author_rank: Unknown
timestamp: November 22, 2022, 03:41:19 pm
content: I knew it for a long time. Often such relays also have endurance rating with a nib not removed, and it's much worse. These relays are sealed for PCB washing, not use.

author: voltsandjolts
author_rank: Unknown
timestamp: November 22, 2022, 03:50:44 pm
content: Datasheets need to call this out, in bold, on the front page...but they don't.ThisTE relay datasheetmentions it only in the order part number spec:"Wash-tight plastic case with knock off nib"But doesn't mention that leaving the nib on (sealed relay) may reduce life by 50% (as per app note above).I sense that a lot of failures have been caused by this.

author: mawyatt
author_rank: Super Contributor
timestamp: November 22, 2022, 04:40:55 pm
content: Interesting!!Any speculation as to why the premature failure when sealed, rather than not?Best,

author: voltsandjolts
author_rank: Unknown
timestamp: November 22, 2022, 04:43:20 pm
content: No need for speculation, it's in the app note linked in OP.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 22, 2022, 04:56:14 pm
content: Quote from: mawyatt on November 22, 2022, 04:40:55 pmThe appl. note from the start gives some explaination: contact arcing produces pollution and with venting some of this can escape, possible even through the rather small hole.I would expect expecially an build up of NOx to possibly cause intenal corrosion that could change a little.The appl. note also tells that is can be an advantage to keep the contracts sealed under certain conditions, especially low load and a dirty environment.

author: mawyatt
author_rank: Super Contributor
timestamp: November 22, 2022, 06:16:36 pm
content: Quote from: voltsandjolts on November 22, 2022, 04:43:20 pmThanks, didn't bother to read the app note, or as we say RTFMBest,

author: coppice
author_rank: Super Contributor
timestamp: November 22, 2022, 06:24:11 pm
content: There are a few of these "remove after assembly" issues with numerous parts. Often connectors and electromechanical parts. Often they aren't properly described in he documentation. Its like a craft skill of those in the know. Its our little secret. Don't tell the plebs, or they'll all get it right.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 22, 2022, 10:42:43 pm
content: never heard of this phenomenon "venting" the things i saw is contacts arcing, some on it can be removed with capacitors in parallel on the relay contactsIf you power motors you may have some inrush current who will gradually destroy the contacts surfacesInductives or Capacitives loadsyou dont specify by spectacular what is driven by the relay(s) you can use SSR's instead ?

author: wraper
author_rank: Unknown
timestamp: November 22, 2022, 10:51:17 pm
content: Quote from: coppice on November 22, 2022, 06:24:11 pmI've seen plenty of buzzers with sticker not removed, a positive side effect it makes them less annoying. 7-segment LED displays more often than not still have protective film on them which reduces brightness and makes them look fuzzy. If it's some Chinese brand product, you can be 95% sure protective film was not removed.

author: theleakydiode
author_rank: Regular Contributor
timestamp: November 23, 2022, 05:17:29 am
content: I had no idea, the more you know.

author: Berni
author_rank: Super Contributor
timestamp: November 23, 2022, 06:22:32 am
content: Interesting, i never heard of this before.This should definitely be explained on the front page of the datasheet.

author: coppercone2
author_rank: Super Contributor
timestamp: November 23, 2022, 12:56:21 pm
content: this makes sense to me because its a closed plasma reactor.this is the old 'don't rush your engineers because something is simple and let them read the entire datasheet'

author: Siwastaja
author_rank: Super Contributor
timestamp: November 23, 2022, 02:50:58 pm
content: Quote from: coppercone2 on November 23, 2022, 12:56:21 pmIt would be helpful though if datasheets did not completely omit critical information just for fun and games.I'm fine it being on page 15 footnote, I read datasheets completely and carefully enough, every engineer should. But it needs to be stated clearly, not like "there exists a nib", but "remove the nib after assembly and wash".