Make-Before-Break or Break-Before-Make? What if the datasheet doesn't specify? - Page 1
Forum section: electronics / projects

author: Yansi
author_rank: Super Contributor
timestamp: July 19, 2016, 08:25:21 pm
content: Hi!I am currently very very pissed by some Würth expensive rotary 8-throw switch, that is fucking shorting neighbouring contacts when the shaft is not in position.The datasheet does not specify, if the switch is MBB or BBM type one. So what is the default, if not specified? Or do they think the design engineer should thoroughly test every switch if it is MBB or BBM? Wtf?!!It very much pissed me off, as I was hunting for a software bug almost the whole day, couldn't find anything at fault... until I grabbed spare one and started to verify the switch function with a multimeter.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: July 19, 2016, 10:50:00 pm
content: Rotary switches are usually designated shorting or non-shortingIs it the Wurth WS-RTV series you are using? They are the only result I can find but are catagorised as an octal DIP switch, not a rotary switch

author: Yansi
author_rank: Super Contributor
timestamp: August 31, 2016, 04:53:00 pm
content: it's this one:https://katalog.we-online.de/em/datasheet/481RV12172100.pdfAnd BTW, the LED used in it suck a lot too! Pisspoor brightness, and also pain in the ass to work with, as they are connected anti-parallel, but each having different forward voltage and very different brightness!Disappointed with such pricey component.

author: Yansi
author_rank: Super Contributor
timestamp: August 31, 2016, 04:57:51 pm
content: WOW!!! Those fucking bastards from Wurth!! The datasheet was updated and it is now specifying, that the rotary part is shorting.Look, this is the datasheet I have worked with, downloaded few months ago:

author: Dave
author_rank: Super Contributor
timestamp: August 31, 2016, 06:21:59 pm
content: They included a vital piece of information which was previously missing in their datasheet. Which part of this makes them bastards?

author: Siwastaja
author_rank: Super Contributor
timestamp: August 31, 2016, 06:49:30 pm
content: It's indeed poor design that the antiparallel two-color LED has minimum luminous intensity values differ by factor of 6. Also, the antiparallel configuration misses the otherwise easy chance to get yellow color out of the thing. I understand that antiparallel bi-color LEDs exist for those relatively rare cases where they are wanted for whatever reason, but why choose this configuration in a specialized product like this, when it clearly decreases the usage value - it can even be the last straw, completely preventing the usage of a part that's otherwise exactly what the designer needs.Huge plus for fixing the original issue, though. It's mentioned in the revision table, so they did not try to cover their tracks.Mistakes do happen, even to highly regarded manufacturers.

author: Yansi
author_rank: Super Contributor
timestamp: August 31, 2016, 07:14:19 pm
content: Quote from: Dave on August 31, 2016, 06:21:59 pmThat they have already fixed the issue well over a year ago, but haven't updated the PDF file on their damn website, which has cost me half a day debugging a custom design with this part.

author: calexanian
author_rank: Super Contributor
timestamp: September 01, 2016, 04:50:52 am
content: Eh, looks kinda cheap and fragile. Not giving me a real feeling of confidence. I might design with a encoder over this thing.

author: RobK_NL
author_rank: Frequent Contributor
timestamp: September 01, 2016, 02:10:55 pm
content: In the few cases where I didn't find some relevant information in a datasheet, I found that asking usually helps. This is certainly true for Würth; they are always extremely helpful.

author: Dave
author_rank: Super Contributor
timestamp: September 01, 2016, 02:44:39 pm
content: Are you saying that asking is Würth the effort?

author: klunkerbus
author_rank: Unknown
timestamp: September 01, 2016, 02:45:19 pm
content: If the datasheet doesn't say, I assume it could be either, and even be inconsistent from position to positionEDIT: and if that matters, yeah it's time to ask or look for another option

author: Yansi
author_rank: Super Contributor
timestamp: September 01, 2016, 10:29:33 pm
content: I would have chosen a different part myself, but I was given this thing. It was a "direct order" to make it with this part, wasn't my choice, but my fault to predict some property of that damn thing and f*cking negligence from Wurth that they couldn't update the datasheet.Everyone seems to be a general after a war, but let me tell you, you would sing a different song if it would cost you one whole design! And also it was done quite in a hurry, no time to ask the support (if they would ever respond to such small fish).

author: dom0
author_rank: Super Contributor
timestamp: September 01, 2016, 10:36:48 pm
content: Quote from: Dave on August 31, 2016, 06:21:59 pmThe "(shorting)" drawing actually implies BBM/shorting behaviour even without the text (the mostly unbroken circumfence of the switch circle between the contacts - if it were MMB/non-shorting these wouldn't be there). This is iirc even standardized in some crufty DIN standard.Of course, writing it there in plain text is much better and should've been done in the first place.Edit: A similar convention seems to exist in the US (presumably):