Industrial 24V connectors

[741]

I'm working on a 'backup' industrial smoke alarm; we need to connect 4 'wires': 2x Power (24V, 0V) and 2x 1A MOS relay contacts.

Some locations might be outdoors (somewhere in a factory grounds); would a connector (and I suppose cable) rating of IP64 be appropriate for most such places?

What are suitable/typical ways to connect to "industrial 24V"? Actual cable types, plugs, receptacles. The industrial 24V scene is new to me.

I do not even know how we would attach to the existing power (DIN?)

I think we'd like a PCB-mount connector - but we are open to suggestions. Maybe a captive cable would be more robust.

Related query - what is the typical protection I need to add on the power lines? In this case, we have a very low power sensor and I think we can simply use a linear regulator.

So we would be guarding against incoming noise (ferrite beads?) and excessive voltage (maybe a resistor in series with a TVS, which should be able to shunt regulate).

[penfold]

Are you working to any specific international standard? I know theres a few for smoke detection/fire suppression, but the word "backup" is suggesting to me that its not "vital" in your case.

I would imaging IP64 should be suitable, if the cable is passing through "factory grounds" then it will need protection in either a conduit or some armoured cable. The M12 connector system available from many brands is great for industrial applications, its compact and robust and there's pretty much any permutation of connector mount from free-wires, pcb mount and in-line cable mount... and its reasonably cheap especially if you're only using 4 wires.

If you're "combining" existing wiring with your own connectors, there's a few options from potted/moulded junctions to in-line cable mounded connectors with which you can attach to existing wiring or assembled connectors.

Noise considerations is a must, a typical power line EMC filter will have some common mode filtering and differential mode filtering along with protection against transients... the EMC tests (and pass criteria/acceptable failure modes) to which your device will be subject to should be detailed under any top level IEC standard for smoke detector systems... I would highly recommend researching those specifics prior to taking random advice on here and committing to a design.

[themadhippy]

 purple ceeforms are the normal 24V IP rated industrial connector,but ive only seen them with 2 or 3 pins,plus there on the large size.The other option maybe the bulgin buccaneer

[ajb]

M12 connectors are probably a reasonable choice for external connections, they're quite common for sensors.  Just be aware that there are a bunch of different key types, so you have to match the mating gender, shell gender, pin count, and key type to get connectors that will mate.  Some keys are sorta-standardized for certain applications, but I think the only application where that's really strict is for the connectors designed for ethernet.  TE makes some field-installable M12 plugs with screw terminals that are surprisingly cheap and great for making test harnesses.

For connections that will be inside of a control cabinet or other enclosure, spring- or screw-terminals are ubiquitous in industry. 

Everything else depends a lot on the intended application, which will inform how robust it needs to be, but you should probably plan for reverse polarity protection on the power inputs and overcurrent/short circuit protection on the MOS outputs at a minimum.