# Quick disconnect for cables ?



## Pete Thornton (Jan 2, 2008)

I have a situation where I want to hastily remove a servo from a loco, and I want to be able to just pop the cable apart without worrying about the connectors.

My 'smart watch' has a magnetic connector on the charger cable that holds it against the watch side so the pins make contact - exactly what I need - except I need a 3-pin connector.











Anyone ever seen anything like that and know a source ?


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## Greg Elmassian (Jan 3, 2008)

I have a bluetooth headset that has a 4 pin magnetic connector.

But Pete, while I'm sure you could find such an animal, it would cost you a lot.

What price will you pay for this connector?

Greg


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## Pete Thornton (Jan 2, 2008)

> What price will you pay for this connector?


Well, the whole loco cost upwards of $700, so if I can't get the servo wired it will all be in vain.

Maybe I can buy the headset and steal the cable! Who made it?

Edit: on looking around in more depth, I found several possibilities, including this:
http://www.aliexpress.com/item/Hot-...est=201526_1,201527_1_71_72_73_74_75,201409_1

Not to mention these guys 
http://cfconn.manufacturer.globalso...om/3000000217371/36109/Magnetic-connector.htm
who have this little beauty:


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## riderdan (Jan 2, 2014)

Have you thought about making your own? I'm in the middle of an experiment using tiny (think pencil lead) rare earth magnets to simulate brake hoses between cars. As part of the experiment, I've attached wires to the magnets inside the "hoses" so that they can be used to conduct electricity between cars for lights. If you use conducting glue, you can easily attach wires to magnets--so I think it wouldn't be hard to make what you want. Since you control the magnet polarity, you could also make it "impossible" to incorrectly connect.

Just a thought.


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## Greg Elmassian (Jan 3, 2008)

The one that is the charging adapter looks good, 18 bucks and you still need to connect to the micro usb, but should handle about an amp.

The Aliexpress ones are great of course, but minimum orders of several thousands each will probably put it out of your price range.

I like the idea.

Greg


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## BigRedOne (Dec 13, 2012)

I would not trust a magnet for a servo connection. (Though my R/C background is in aviation.)

Would servo extension leads work for you? They come in a variety of sizes starting around 6".


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## Pete Thornton (Jan 2, 2008)

BigRedOne said:


> I would not trust a magnet for a servo connection. (Though my R/C background is in aviation.)
> 
> Would servo extension leads work for you? They come in a variety of sizes starting around 6".


Running a steam engine with a dodgy servo connection is a bit less traumatic than flying a plane. And no - servo extensions don't solve the problem of fast disconnect.

The magnet idea is quite a good one though. I'll have to think about that.

Greg - I thought the charging adaptor looked like a good option - as you say, I'd have to figure out the USB connector or just solder directly to the exposed pins.


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## East Broad Top (Dec 29, 2007)

Pete, what are you trying to accomplish with these connectors where a servo extension would take too long or be too difficult to disconnect? Is it in an area where finger access is troublesome to put them together?

Later,

K


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## Greg Elmassian (Jan 3, 2008)

Pete, maybe you could find a micro-usb extension that had a female already wired. I looked about for one, you might find it, or maybe buy a micro usb socket.

Regards, Greg


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## Pete Thornton (Jan 2, 2008)

East Broad Top said:


> Pete, what are you trying to accomplish with these connectors where a servo extension would take too long or be too difficult to disconnect? Is it in an area where finger access is troublesome to put them together?
> 
> Later,
> 
> K


Kevin,
This is for the Dordlebug (a k a A-Dora-ble Doodlebug.) You saw it at your Dad's place. I have to get the steamer unit [Dora] out of the plastic shell a.s.a.p. when it stops.

As the front truck is pivoting, I can't mount the servo in the car - it has to be able to swivel with the truck. When I lift the body off, I'd like the servo cable to the rcvr to disconnect easily, without needing two hands. Hence I'm not happy with the servo extender idea.

My Pebble smartwatch has a magnetic charger cable, which gave me the idea. I suspect we'll find something. Then maybe an app for my smart watch to drive the loco's WiFi rcvr so I can leave the phone in my pocket?


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## placitassteam (Jan 2, 2008)

Pete, On my passenger cars I made my own connector using discarded wheel pick-ups to power the lights. The flat springs in the roof simply make contact with fixed contacts in the body when I install the roof. When the roof comes off the connection is broken.


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## CliffyJ (Apr 29, 2009)

Pete, if you have the opportunity that Winn describes, you could also hack an older-style largish relay for its contacts.


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## Phippsburg Eric (Jan 10, 2008)

could you have a brass or spring bronze finger arrangement which could make electrical contact? Thinking of something the scale of the skates on an LGB Loco. While the servo lead is small, the contacts could be large enough to deal with any slop in locating the car body. Drop the body on for contact, pick it up to work engine... Don't even mess with the wire.


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## riderdan (Jan 2, 2014)

Phippsburg Eric said:


> could you have a brass or spring bronze finger arrangement which could make electrical contact? Thinking of something the scale of the skates on an LGB Loco. While the servo lead is small, the contacts could be large enough to deal with any slop in locating the car body. Drop the body on for contact, pick it up to work engine... Don't even mess with the wire.


This is also how the LGB powered tenders work. The motor block has a pair of brass tabs on top. The body of the tender has two posts, each with a screw in the top of it. The wires for the tender lights are held down by the screws (like a screw terminal) and when the tender is assembled the posts hold the screw heads in contact with the brass tabs on the motor block.


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## Pete Thornton (Jan 2, 2008)

Phippsburg Eric said:


> could you have a brass or spring bronze finger arrangement which could make electrical contact? Thinking of something the scale of the skates on an LGB Loco. While the servo lead is small, the contacts could be large enough to deal with any slop in locating the car body. Drop the body on for contact, pick it up to work engine... Don't even mess with the wire.


I knew I could count on you guys for good ideas. I hadn't thought of that one.
Problem is that the steam truck is allowed to move a lot to deal with curves and track issues. However, I just fixed a brass sheet on the top pivot as the heat was getting to my wood. Maybe I can use the side that isn't touching the truck to pass the signals.


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## dbodnar (Jan 2, 2008)

*Magnetic Connectors - one way to do it*

Pete - is this what you had in mind:

https://www.youtube.com/watch?v=5MMhxv2vNRQ&feature=youtu.be

Details on my web page here:

http://trainelectronics.com/Magnetic_Connectors/


dave


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## Pete Thornton (Jan 2, 2008)

dbodnar said:


> Pete - is this what you had in mind:
> 
> https://www.youtube.com/watch?v=5MMhxv2vNRQ&feature=youtu.be
> 
> ...


Dave,
That is exactly the functionality I was looking for (though the wiper idea proposed by Eric might be better!) 
Only one question occurs to me - with 3 magnets, you must have some flex in the holder so that all three can make contact? A stiff glue medium will make one not quite contact the other?


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## Pete Thornton (Jan 2, 2008)

> could you have a brass or spring bronze finger arrangement which could make electrical contact?


I'm sure I took some spring-loaded plunger-type pickups off something recently. I certainly have lots of Accucraft coach wipers!

I did find "pogo pin" connectors - which have springs in them.
http://www.aliexpress.com/item-img/...g-needle-probe-Free-Shipping/32238456611.html


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## Pete Thornton (Jan 2, 2008)

Whoo Hoo . . Thanks Eric for the idea. I had the bits in the drawer, so I spent a couple of hours making the connection. Here's the underside of the 'pivot plate' with the two extra contacts for the truck. The frame is the ground.











And this is the truck, with a pair of shortened Accucraft coach wipers mounted on plywood (it doesn't melt quite so quickly.) The outer end rests on the gas tank valve shaft, and I'll have to move the gas handle so I can reach it - but as I don't usually adjust it when the body is on, it may be OK.











And finally a full-blown test, using my new WiFi receiver. No problemo!


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## CliffyJ (Apr 29, 2009)

Atta boy, Pete!


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## placitassteam (Jan 2, 2008)

Glad to help with ideas. Looks like between several of us we got the job done. Hope it works well for you.


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