Looking for a circular connector with pin connect sequencing - Page 1
Forum section: electronics / projects

author: ogoun
author_rank: Contributor
timestamp: February 10, 2022, 07:09:49 am
content: Hi,I am working on a project that will be used in a hazardous environment, and am looking for a 12 pin circular connector pair (bulkhead/flange for the device, free hanging mate for its power and comms cable).I know what I am looking for, and have used them before, but cant find a google friendly way to describe it..The male pins in the bulkhead connector (mounted on the device chassis), are of two types. One type is for power, and are usually a bit thicker than the others (I dont really care about this), and are longer than the other pins(i do care about this!).This is to ensure that when the plug is inserted into the socket the power and ground pins are electrically mated first, and the remaining signal pins mate after this. I am sure there is a name for this configuration, but best I found was "pin sequencing".This is to ensure that a spark is unlikely, since the device is energised when it sees a particular signal on one of the signal pins. Imagine something like a relay.. e.g. one of the signal pins gets earthed to energise the device's internal relay, which internally connects the power from the plug to the rest of the circuit. It is more sophisticated than this (and no relay🙂), but the concept is the same.Idea is that hotplugging the device wont be likely to cause a spark.Can anyone please point me in the right direction to finding such a circular plug config? Ideally, 12 contacts, 3 power (+24v, 0v, gnd), and 9 signal..Cheers,Pete

author: Berni
author_rank: Super Contributor
timestamp: February 10, 2022, 07:20:47 am
content: This is called make-first/break-last contacts.One example is this:https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Catalog+Section%7F82021_CPC_sections1-5%7F0807%7Fpdf%7FEnglish%7FENG_CS_82021_CPC_sections1-5_0807.pdf%7F201611-1The Tyco contact pin 212618-2 for use in the Tyco CPC and CMC series of circular connectors.By the looks of it you simply assemble the connector with the longer pins in the locations you want.

author: voltsandjolts
author_rank: Unknown
timestamp: February 10, 2022, 10:39:44 am
content: Quote from: ogoun on February 10, 2022, 07:09:49 amAre you designing a system which must beintrinsically safe?

author: Henrik_V
author_rank: Regular Contributor
timestamp: February 10, 2022, 01:06:47 pm
content: I would pick up the phone and ask LEMO (lemo.com) ...

author: ogoun
author_rank: Contributor
timestamp: February 10, 2022, 06:29:13 pm
content: Quote from: voltsandjolts on February 10, 2022, 10:39:44 amyes, that is it. Zone 1, gaseous. Using encapsulation, so IECEx mb.

author: geggi1
author_rank: Frequent Contributor
timestamp: February 10, 2022, 08:08:32 pm
content: Check the sites of stahl and Cooper Croues Hinds. They have high quality atex/iecex connectors.https://r-stahl.com/de/global/home/https://www.crouse-hinds.de/en/I have used many over the years.I have also used a brand called Icore made in thermoplastics. Thos connectors you can get in industrial type and Atex. Its many years since I used it before Iecex, but they have probably also got that certification now.Think that RS-components had them in the past.

author: ogoun
author_rank: Contributor
timestamp: February 11, 2022, 07:54:28 am
content: The problem with iecex or atex rated connectors is cost..For my encapsulated design (60079-18, Exm, Zone 1, gaseous), the standard allows a non haz rated connector, so long as the load is disconnected from the supply before mating or unmating the power pins.So, if I can find such a connector (called Mate First, Break Last, or MFBL), for its power pins, then my BOM costs will be quite a bit lower🙂Cheers,Pete

author: voltsandjolts
author_rank: Unknown
timestamp: February 11, 2022, 11:16:57 am
content: I'm not familiar with IS requirements and have question:If the connector must have these mating characteristics to prevent a spark, then the cable is carrying signals which are capable of creating a spark. So what happens if the cable is accidently cut or somehow damaged (not uncommon in an industrial environment), exposing conductors and creating risk of a spark? It doesn't sound 'intrinsically safe' now. Or is the energy limited such that a spark, from a cut cable, would not have sufficient energy to ignite the specified gas environment? If so, then why have the connector mating requirements?

author: ogoun
author_rank: Contributor
timestamp: February 12, 2022, 12:42:51 am
content: You are correct.For hazardous environment protection, IECEx or ATEX, my application is compliant with the encapsulation method (Exm, 60078-18), not the intrinsically safe method (Exi, 60078-11). Both methods solve the haz enviro problem, but in very different ways.My design uses about 60 watts, with 24 volts nominal input, so a cut cable will spark. This is where metal body connectors, armoured cable, and "pull tests" are required.Designing for intrinsically safe seems almost impossible if the design will use more than about a watt or so.. Lots of voltage, current and energy limitations.Cheers,Pete

author: voltsandjolts
author_rank: Unknown
timestamp: February 12, 2022, 07:02:02 pm
content: Sounds like sticking withcertified connectorsis the way to go.