Need waterproof connectors that are not assemble-able without being waterproof - Page 1
Forum section: electronics / general

author: ocset
author_rank: Super Contributor
timestamp: May 12, 2018, 09:46:24 pm
content: Hello,We have multiple LED lamps that will be in a bare room. They are all supplied by 48VDC. There are multiple connectors to each lamp. We need all of these to be waterproof, as the room regularly gets sprayed with a deluge of cleaning water. If any connector is not watertight then the 48VDC bus will get shorted and it will take us ages to find the “guilty” connector that’s leaking. Is there any form of waterproof connector that can be reliably assembled and be definitely waterproof?These ones just don’t look up to it…https://www.toolstation.com/shop/p27346

author: ChristopherN
author_rank: Unknown
timestamp: May 13, 2018, 12:38:13 pm
content: I've used cable joiners like the ones you linked on a ship once, they worked good but were a pain to install in tight spaces.I don't remember the part number, but I've just seen an ad on Digikey for similar ones that look better:https://www.digikey.com/products/en?keywords=ficx&pageSize=

author: ocset
author_rank: Super Contributor
timestamp: May 13, 2018, 12:45:25 pm
content: Thanks, We are also thinking of cheaply "jacking" it, and using any old non waterproof connector, and shoving a small thin plastic "tube" over it when connected. and then having kind of jubilee clips pull tight at each cable entry end of the connector, so as to pull the plastic so it seals around the cable and connector, giving an element of waterproof-ness

author: jeremy
author_rank: Super Contributor
timestamp: May 13, 2018, 12:49:59 pm
content: How many amps? I like the M8/M12/M16 connectors for something that is IP67 or IP68.

author: ocset
author_rank: Super Contributor
timestamp: May 13, 2018, 12:57:04 pm
content: less than 0.5A in each connectorBeing super-cheap, we are even thinking of a bit of choc block, wire into each screw clamp so they are connected, tie a knot in the wires as they go into the choc block for strain relief, then a small plastic bag around this, then elastic band or jubilee-clip round this for water proofing it tight to the wires.

author: ChristopherN
author_rank: Unknown
timestamp: May 13, 2018, 01:19:32 pm
content: Have you looked at super cheap heat shrink / solder / glue connectors?https://www.ebay.de/itm/10X-Waterproof-Solder-Sleeve-Heat-Shrink-Butt-Wire-Splice-Connector-16-14AWGBG/183218888232?hash=item2aa8b25e28:g:PBMAAOSwPbla3ZwkI have not used those.

author: janekm
author_rank: Unknown
timestamp: May 13, 2018, 01:43:59 pm
content: Have a look at connectors designed for automative use, like TE/AMP Superseal range:http://uk.farnell.com/amp-te-connectivity/282087-1/socket-housing-3way/dp/150423They're fairly cheap for this quality of connector and widely available.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: May 13, 2018, 01:59:35 pm
content: Various automotive sealed connectors are available that would work and are inexpensive. For example, the Molex MXP120 series:https://www.mouser.com/ProductDetail/Molex/34900-2120?qs=sGAEpiMZZMs7eK6h2EBtKr%252bv4R4ArMXcnh9E5%2f6%2fMQI%3dAlternatives include connectors for solar PV, search Digi-key here:https://www.digikey.com/products/en/connectors-interconnects/photovoltaic-solar-panel-connectors/326Edit: Beaten to the punch by janekm.

author: ocset
author_rank: Super Contributor
timestamp: May 13, 2018, 02:08:20 pm
content: ThanksI wonder just how conductive cleaning water is going to be?I mean, the most conductive type of water is sea water, and that has a Rho of 0.2.Therefore, a rectangle of sea water of length 1cm and area 1mm^2 would have a resistance of 2kOhms.So its not even very conductive…..i don’t see short circuiting being a great problem. I wonder why there are so many waterproof connectors?

author: SeanB
author_rank: Super Contributor
timestamp: May 13, 2018, 04:38:40 pm
content: More that copper corrodes really fast in contact with sea water, and this corrosion travels up the wire causing damage far up the cable with time and applied voltage. The waterproofing is there to keep corrosion at bay.

author: dmills
author_rank: Super Contributor
timestamp: May 15, 2018, 05:17:26 pm
content: Keeping water out is **Really, really** hard, seriously the stuff is referred to as the "universal solvent" for a reason.Just to give you a flavour of the failure modes...Ok you have a cable coming in thru a waterproof gland, fine, but if the outer jacket of the cable gets damaged you will, sooner or later get water inside the box because it sneaks down between the jacket and the cores.Single wire? Same thing happens, but it sneaks down between the conductors and the jacket.PVC cable insulation.... Waterproof right? Well, not reliably so much as it turns out, we had a nightmare with this in a subsea application (Vendor had changed the composition without telling us).Electrolysis is the big threat when you have wet electrics, not short circuit, it is amazing to see how quickly a power connector left power on in sea water will rot.Personally I like overmoulded connections with PUR in that kind of environment, and even then you have to prepare the cable PUR jacket so it wets out properly with the compound.From the sound of it, this is food prep area? The water may well contain bleach or other anti microbial compounds, treat it as salt water.Regards, Dan.

author: Nerull
author_rank: Frequent Contributor
timestamp: May 15, 2018, 09:20:02 pm
content: Quote from: dmills on May 15, 2018, 05:17:26 pmAt work we were using thermocouples to measure the temperature of a water stream through a hose. Initially they didn't want to buy a probe type and just used the beaded wire type, sealed into the hose with RTV. The thermocouple wire then ran upward to a fluke 52 thermometer sitting several inches above the level of the hose.One day one of the thermometers stopped working, and we discovered that water had traveled up through the insulation on the thermocouple wire, through the connector, and dripped right into the meter.

author: dmills
author_rank: Super Contributor
timestamp: May 15, 2018, 10:38:24 pm
content: Quote from: Nerull on May 15, 2018, 09:20:02 pmSounds about right!Now try it 2,000 meters below the surface, the stuff manages to do amazing things under that kind of pressure....Regards, Dan.

author: ocset
author_rank: Super Contributor
timestamp: May 16, 2018, 04:55:17 am
content: Thanks,It now sounds to me that this contact-less lighting system is going to be really useful.......https://greengage.global/clip-on-led-lighting-for-poultry-and-swine-farming/..there are no metal contacts, the lights just get clipped to a cable...the clip is made of ferrite.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 16, 2018, 05:51:10 am
content: Quote from: treez on May 13, 2018, 02:08:20 pmThe problem isn't only the initial conductivity. The issue is that even a very slight leakage current through the water causes some electrolysis, dissolving exposed metal to the liquid in question. Now, the liquid gets more conductive due to this, leakage increases, and we have a runaway loop.So, while you could get away for quite some time with high-quality distilled water and very carefully cleaned surfaces (so that little conductive contaminants get into the water), even that fails eventually (weeks, maybe months?) since conductive contaminants cannot be fully removed, and once the process starts, it will accelerate exponentially. With clean tap water, it happens in just hours or days.Now, if the water changes very rapidly (i.e., the water is not trapped), that slows down the process because the metal ions are washed away, and fresh, less conductive water is applied all the time. Bad news: it'll still happen too soon.So yes, you'll need waterproof connectors.

author: dmills
author_rank: Super Contributor
timestamp: May 16, 2018, 10:17:02 am
content: I have seen those ferrite transformer clip based things being played with for ATEX work, trouble is the wiring radiates, so the twisting is kind of important to minimise the RF leakage, and the explosives guys take a really dim view of random wires pumping RF power into their detonator wiring.....It has a place, but it is not going to win any efficiency awards, and it has issues that are sometimes not immediately obvious.Regards, Dan.

author: bob225
author_rank: Frequent Contributor
timestamp: May 16, 2018, 10:26:44 am
content: Only way to get a ultra water tight joint its to pot it, I take all the fittings are ip ratedGel filled crimps are another option

author: ocset
author_rank: Super Contributor
timestamp: May 16, 2018, 11:24:54 am
content: QuoteThanks, i must admit we have a lot of people wanting to know what these might be?

author: dmills
author_rank: Super Contributor
timestamp: May 16, 2018, 01:04:59 pm
content: Long RF pair that is hopefully twisted, with effectively inductors at random intervals, this does not play particularly nice with transmission line theory and the load impedance seen by the driver is going to be fairly random (More so if devices can be added in an adhoc manner).Then you have the issues with coupling into other nearby wiring (As I say, this risk makes mining explosives types real twitchy), and the potential for a lot of volts across the line if you happen to be a 1/4 wavelength away from the end of the loop. If run in steel conduit you may add a lot of losses as well as changing the line impedance.As I say, it has it's place, but it wants the installation to be designed by folks who get transmission line behaviour.73 Dan.

author: Rerouter
author_rank: Super Contributor
timestamp: May 17, 2018, 08:08:36 am
content: The way I go about it with connections underneath city buses is use small diameter plugs, slip over a 10cm length of 4:1 glue lined heat shrink, plug it together, test it, then slip the heatshrink over and apply even heat until you see the glue leak out both ends around the entire circumference.To break the connection, just slice along the connector seam through the heatshrink with the power off, you can generally get about 3 re-seals out of this method before you need to remove the old heatshrink.I would not trust it to be left underwater, but it defiantly cops high pressure hoses, rain backspatter and puddles without grief after at least 3 years since I started doing it.