Author Topic: waterproof wire connector  (Read 6108 times)

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Offline AdminTopic starter

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waterproof wire connector
« on: December 29, 2006, 02:33:21 PM »
I am looking for miniature waterproof cable connectors for my open hull robot fish (water is allowed inside i.e. not a closed hull).

The problem I have is most waterproof connectors are designed for submarines . . . or at least for UUV's the size of a small car - meaning they are huge (1+ inches in diameter, and 2 inches in length).

I need something that isnt more than an inch in length maximum (male and female connectors combined), and no more than half an inch in thickness. At the moment I just need it for two wires (~22 gauge), carrying 2amps current each. I would be interested in waterproof connectors that are even smaller, with 3+ positions at much less current for another application, but havnt looked into that yet.

The ONLY manufacturer I have found for something I want is EDAC, offering these waterproof connectors:
http://www.edac.net/downloads/EDAC%20WATERPROOF_CATALOGUE.pdf

the 566 series is perfect, but alas, digikey is sold out . . .

anyone know of other companies offering either the EDAC connectors or some other connector?

Offline Militoy

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Re: waterproof wire connector
« Reply #1 on: December 30, 2006, 10:07:25 AM »
You might try Conxall connectors - also available on Digi-Key. They're rated for IP67 service, and can be run submersed for long periods - especially if coated with silicone vacuum grease, or even RTV. Their smallest models are the Micro-Con-X line, with the Mini-Con-X and Multi-Con-X models having the same properties, only larger, higher current, and more contacts.

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Re: waterproof wire connector
« Reply #2 on: January 03, 2007, 09:02:39 AM »
they are a bit too long, and still a bit too wide, but small enough to at least fit in my robot . . .

since they are cheap ill order each type of the micro size and see what works best.

thanks!

Offline Militoy

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Re: waterproof wire connector
« Reply #3 on: January 03, 2007, 09:09:16 AM »
I forgot to mention that they have an ultra-miniature line (smaller than the Micro-Con-X), made for sensors, encoders, etc. You might want to look those over, before settling on the Micro-Con's.

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Re: waterproof wire connector
« Reply #4 on: January 03, 2007, 01:22:05 PM »
so I went through the datasheets and it appears that the nano-mizer product fromConxall is what i want . . .

http://www.conxall.com/New_Products/npb551.pdf

so i tried emailing the company . . .
http://www.conxall.com/E-Mail/e-mail.html
three of the email addresses return a "Delivery to the following recipient failed permanently" error . . .
the service address doesnt return an error, so maybe they will reply back, but I doubt it . . .  :-[

ok so enough with the ranting, I need some help . . . this is the email I sent:
Quote
I am looking for the smallest waterproof mating connectors on offer.
Emphasis on smallest diameter and shortest length (after mating male
and female ends).

Two prong is preferred, but 3 prong is acceptable. It will be for DC
of no more than 8.5V, and no more than 2.2A current.

Sorting through your product sheets, it appears the nano-mizer product
is what I want. However, I am unclear on what mating attachments fit.

Can you please advise on which products (both the male and female
ends) would work best for me?


I am fusing the ends of a battery to one end, and want a quick battery disconnect that is water proof. The other end goes to my power supply circuit:

battery wires -> sheilded wire -> waterproof connector male end -> waterproof connector female end -> sheilded wire -> circuit board

the connector will be submersed, while the other parts will not.

looking at the datasheet, I think the part labled 'STRAIGHT FEMALE SINGLE ENDED
SNAP LOCK WITH LOCKING RING' will connect with 'STRAIGHT MALE SINGLE ENDED
SNAP LOCK.' is this correct? the threaded kind is out of the question, because total wire length will be only a little over a foot - making overtwisting an issue.

aquatic robots = hard to design  :P

Offline Militoy

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Re: waterproof wire connector
« Reply #5 on: January 03, 2007, 02:34:21 PM »
I would try a shot at answering your question myself - but I make up my own cables, and I've never used their molded cable assemblies; so my answer would be just a "Best Guess". I don't recollect what state you're in, but Conxall's website has a rep/distributor section with phone #'s and web addresses for a lot of Switchcraft Reps in various states. I would skip the distributors - they usually just sell by part number. The factory phone # will usually put you in touch with a tech rep, but with some large companies this can be hit-and-miss. The reps listed work on commissions from sales generated in their territories - so they're usually very knowledgable and very willing to help out customers.

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Re: waterproof wire connector
« Reply #6 on: February 02, 2007, 01:30:48 PM »
decided to just make my own waterproof connectors . . . ill write a tutorial on it some day . . .

so my next question, where can i find waterproof on/off switches (4A, 7V nominal)?

something like these would be perfect in size/dimensions:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2071
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2656

except when I called them up, they said the water proof rating isnt good enough for submersibles :(
(i also asked about their connectors, which also arent submersible)

couldnt find anything on digikey either . . .

Offline JonHylands

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Re: waterproof wire connector
« Reply #7 on: February 02, 2007, 01:54:18 PM »
Admin,

I typically use a magnetic reed switch that is hooked to a MOSFET to turn my AUV on.

Digikey part #: CH402-ND

That gets mounted inside the hull, and I use a removable magnet "key" to activate it.

- Jon

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Re: waterproof wire connector
« Reply #8 on: February 02, 2007, 03:09:26 PM »
Genius! (I actually thought of this myself, but hastily ruled it out before fully investigating . . .)

Is there any reason not to just use the reed switch alone without the MOSFET? Im not doing any highspeed switching, and want something more efficient since I wont be able to aircool the FET, so I'd rather avoid using it if possible . . .

browsing around i found this magnetic reed switch:
http://www.hamlin.com/images/upload/ByCatalogue/pdf/MRPR-3.pdf
(digikey #HE547-ND)

It says its rated for 50W. My absolute worse case scenario requires 44W (8V, 5.5A), but expected average will be ~30W (7.2V, 4.2A). The reed datasheet says 3A max carry but Im not sure what voltage that is based on . . . think one will just work, or can I perhaps get away with two in parallel?

Got a pic of your switch setup?

Offline JonHylands

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Re: waterproof wire connector
« Reply #9 on: February 02, 2007, 03:48:12 PM »
Admin,

I didn't, but I do now...

http://www.bioloid.info/switch/Inside.jpg
http://www.bioloid.info/switch/Outside-1.jpg
http://www.bioloid.info/switch/Outside-2.jpg

The white Delrin piece has a lip, so it is larger outside than inside (thus, the pressure won't push it inside). The aluminum tube has a rare earth magnet inside.

I used to have two of the switches, because I had two separate batteries, but now I just use one.

I just run a MOSFET because its simple, and I don't need to worry about current.

- Jon
« Last Edit: February 02, 2007, 03:49:49 PM by JonHylands »

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Re: waterproof wire connector
« Reply #10 on: February 02, 2007, 04:02:21 PM »
thanks!

Quote
I just run a MOSFET because its simple, and I don't need to worry about current.
but you still gotta worry about current in your FET . . . ive fried so many FET's in my day . . .

i just wanted to make sure i wasnt doing something fundamentally dumb, like passing 4A through it to only have the glass explode everywhere or something . . .

Offline JonHylands

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Re: waterproof wire connector
« Reply #11 on: February 02, 2007, 04:22:26 PM »
The thing is, you're coming close to the carrying capacity of the switch. With a land-based vehicle, its no biggie - you get a current surge, it blows the fuse, you walk over and pick it up.

For an underwater vehicle, it isn't always that simple.

You can get TO-220 MOSFETs that can take 50 amps no problem, like this one:

FQP50N06-ND

for around $1, it offers one less thing to go wrong...

- Jon

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Re: waterproof wire connector
« Reply #12 on: February 06, 2007, 01:50:40 PM »
you wouldnt know anything about spec'ing magnets for reeds, would you? ???

the reed I want to use has a sensitivity of '22-38 A/T' . . . so at lets say .3" away, how many pounds pulling force of a disk magnet do I need?

JonHylands, how many pounds can your magnet pull, and how far away is it from your reed switch?

my other option is just to buy a bunch of different magnet types and try each one . . .

Offline JonHylands

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Re: waterproof wire connector
« Reply #13 on: February 06, 2007, 02:28:14 PM »
I'm using a rare earth magnet that is about 3/16" diameter, and 1/8" long (cylindrical). It has to get within about 1/2" of the end of the switch before it engages. I've got about 1/4" of Delrin between the magnet and the switch when it is fully seated.

The nice thing about those magnets: You can stack them, and it increases the field effect. If you use a piece of aluminum tubing, you can just slide in a couple more magnets behind the first one to get a stronger effect.

Make sure you seal the ends of the tube if you use one - the magnets rust after exposure to even fresh water.

- Jon

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Re: waterproof wire connector
« Reply #14 on: March 01, 2007, 09:10:35 AM »
It works! :D (the reed switch method)

For others who ever need to do this, here are the parts I used:
Digikey # HE505-ND for the high power reed switch

and McMaster # 58605K75 for 'Pressure-Formed Neodymium Disc Magnet 1/4" Dia, 1/4" Thick, 3.5 Pull lbs, Nickel Plated'

I got the nickel plated type because it offers corrosion resistance against water.

Putting two of the magnets in series, I can activate my reed switch an entire inch away! Its all powered up and works, with only like 1 ohm of contact resistance.

Not sure how many amps I can put through it before failure, but at ~7V it shouldnt be a problem . . .

Offline JonHylands

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Re: waterproof wire connector
« Reply #15 on: March 01, 2007, 09:21:44 AM »
I had nickel-plated magnets as well. After a while, they weren't nickel plated anymore. You need to seal them against moisture. It might take a year or so, but the plating flakes off, and then its just a mess.

- Jon

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Re: waterproof wire connector
« Reply #16 on: May 15, 2007, 09:26:46 AM »
So Im having unexpected problems with the reed switch . . .

It normally works, but if I run my robot for awhile, the reed switch no longer turns off when removing the magnet. No magnet, yet robot is still working!

If I unplug the battery, the robot shuts down. If I quickly plug it back in with 5 seconds, it will turn back on without the magnet. If I wait 10+ seconds before plugging it back in it will require the magnet to turn back on . . .

Whats goin on?!

notes:
I have about ~2amps at 7.8V going through it, and the datasheet says it can handle much more.

Offline dunk

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Re: waterproof wire connector
« Reply #17 on: May 15, 2007, 10:07:22 AM »
is there any other sources of magnetic field near by?
this project was driven by servos right? i wouldn't imagine they would generate enough magnetic field to hold the reed switch open...
try testing the running equipment with a compas.

dunk.

Offline JonHylands

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Re: waterproof wire connector
« Reply #18 on: May 15, 2007, 10:12:29 AM »
I would suspect you're running too much current through it. For things like switches and such, you can't look at wattage - the current is absolute for some reason, regardless of the voltage.

Try the MOSFET...

- Jon

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Re: waterproof wire connector
« Reply #19 on: May 15, 2007, 10:39:27 AM »
Quote
is there any other sources of magnetic field near by?
this project was driven by servos right? i wouldn't imagine they would generate enough magnetic field to hold the reed switch open...
yea its a non-obvious problem i think . . . perhaps it has something to do with overheating or magnetic fields caused by high current or something . . .

Quote
Try the MOSFET...
i should have listened to you the first time :-[
doh! ok time to do some rewiring . . .

 


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