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question about a male jack

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#1 donnie3

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Posted 25 January 2013 - 10:33 AM

the male jack that plugs into a goto mount must be positive. im making a connector for a battery i purchased for my mount. i was told not to get a negative jack because it will fry the electrical components. how do you tell if the center of the jack is positive or negative. thanks, donnie

#2 Midnight Dan

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Posted 25 January 2013 - 10:43 AM

To be absolutely sure, you need to check it with a voltmeter.
-Dan

#3 donnie3

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Posted 25 January 2013 - 11:19 AM

midnight dan, im not real savvy when it comes to electronics. not sure how to use a voltmeter, i dont even have one. would the people at radio shack know the difference. surely there is a way to tell just by visually looking at the jack. the makers of the product putting something on the jacks to indicate - or +.thanks, donnie

#4 csrlice12

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Posted 25 January 2013 - 11:41 AM

If you're making the connector using the jack, which is + or - depends on how you wire it, not the jack........

#5 tubehead999

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Posted 25 January 2013 - 12:07 PM

Drop by the Shack and buy one of these....read the instructions!
http://www.radioshac...oductId=4214667

I would say Harbor Freight, where they sell for five bucks...but the closest one to you is 50 miles away...

#6 tag1260

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Posted 25 January 2013 - 12:40 PM

If you're making the connector using the jack, which is + or - depends on how you wire it, not the jack........


YES!! I fly RC and when it comes to charging jacks, you need to make sure of what you are charging because one manufacturer makes their jacks reverse of what is NORMALLY standard. Normally the outside is negative with the inside positive. You can also check the equipment near the socket for a diagram. Most have one.

#7 csrlice12

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Posted 25 January 2013 - 01:41 PM

You could always take the cable and resplice the wires to the opposite polarity.....voila, done!

#8 Midnight Dan

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Posted 25 January 2013 - 01:54 PM

Hi Donnie:

First, some terminology. A jack is the socket on a device that receives a connector. The connector on the end of a cable is usually referred to as a plug. So, you insert a plug into a jack.

In your case, since you're creating the cable yourself, you can wire it any way you want ... tip positive or tip negative. You don't really need a voltmeter unless you want to check your work afterwards. So, for a "tip positive" plug, just make sure you connect the + terminal of the battery to the tip of the plug you're using on the scope end.

-Dan

#9 CJK

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Posted 25 January 2013 - 01:56 PM

the male jack that plugs into a goto mount must be positive. im making a connector for a battery i purchased for my mount. i was told not to get a negative jack because it will fry the electrical components. how do you tell if the center of the jack is positive or negative. thanks, donnie


What mount do you have?

If you are doing any sort of DC wiring, you really ought to get a multimeter. It doesn't have to be fancy, the one linked to above is fine. They are extremely easy to use: here is an excellent tutorial.

-- Chris

#10 Eddgie

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Posted 25 January 2013 - 02:50 PM

Most (but not all) of the plug type sockets are arranged with a positive center pin if they are mounted in a metal holder of any kind.

The reason is simplicity itself. If the outer part of the plug were wired to 12 volts, then the thing it is mounted on will he hot with 12 volts.

The other reson is becase if you did the shell of the connector on the cable, if you let the tip touch anything, it would once again get 12 volts.

Now 12 volts DC is not likely to hurt anything but here is a case where it will.

Suppose you plug a cable with a cigerette lighter type plug on one end into your car, and the outside of the tip was wired hot, if the tip touched the car, you could get a whicked arc.

And this is the way you can test a cable if you don't know how it is wired. Hook one of the wires to the negative pole of a battery and touch the outside of the pin to the hot side. If you get a spark, or you feel the point of contact getting hot, you know which wire is which. Of course is you don't get a spark or don't feel it heating up, the wire you picked is wired to the center pin.


A car battery as mentioned will throw a whicked arc.

I have never personallly encountered a piece of telescope equipment that used 12 vdc tha had the outer part of the tip hot. Every Meade or Celestron mount I have ever owned had the center pin hot and not the outside.

The only time I have ever seen a consumer product where the outside of the plug was positive was on a plastic cased portable CD player.

Sadly though, if you do have the one in a hundred devices that has negative center pin, you can indeed damage the item by using a tip with the wrong polarity.

But as a very reliable rule of thumb, if the socket is mounted into metal, the outside will be at ground potential because they are genearlly using the metal as ground for the electronics.

Again, I have only ever seen one product that had the outer part of the tip wired for 12v. But have never seen a jack mounted in metal that did not use 12v center.

#11 csrlice12

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Posted 25 January 2013 - 03:37 PM

The old Sony Walkmen's I believe had the polarity reversed; but yea, all the 12Volt Astro equipment power converters I've seen have the center pin as positive.

#12 Patrik Iver

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Posted 27 January 2013 - 01:20 PM

Atleast the Vixen SkySensor 2000 goto-controller feed cable is negative tip and positive "shell/sleeve".

#13 hottr6

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Posted 27 January 2013 - 04:37 PM

A male jack is a redundant expression.

Oh, you are talking about electronics. I thought I was in the livestock breeders forum.

#14 Eddgie

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Posted 27 January 2013 - 05:41 PM

Was it in a metal housing, or plastic?

If it was a metal housing, the housing would then have a 12 volt charge, and that is why I said that when the socket is mounted in a metal housing, the tip is almost always postitive.

For plastic, one would have to test it to be sure.

In every case I have ever encountered that the socket was mounted to metal, the tip has been positive.

But the OP did not say what his was mounted in.

#15 Patrik Iver

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Posted 28 January 2013 - 11:47 AM

The Vixen connector is not chassis-mounted.
The handbox has a multi-pin connector into which you plug the main cable set, which then splits into three cable ends; altitude servo-motor with encoder, declination servo-motor with encoder, and the power feed.
The power feed is a female plug (negative center pin), which can be connected to any suitable 12 V DC supply. The standard power supply is a vinyl pouch which holds 8 D-cells, but I don't think anyone would use that in the long term. So the result is that a battery cable is required, and that cable will have a male plug with positive sleeve, which could easily short out on any earthed metal surface, if for example fed from a car lighter socket.

I have no idea how the non-goto Vixen drive controllers are fed, but I'm inclined to guess that they either use the same polarity, or then a physically completely incompatible plug, to avoid frying anything through reversed polarity in case someone happens to own more various Vixen-mounts.

#16 tomcody

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Posted 28 January 2013 - 01:09 PM

Definitely buy a DMM (digital volt meter) and learn to use it. You can get a decent one for $20 - $30. I like some of the brands sold by Lowes and Home Despot in the electric section. To use it set it for voltage, DC direct current,
( as opposed to AC alternating current as come from the wall outlet). Set any range for slightly above what you expect to measure, ( i.e. a 20V range for a 12V battery).
Then the important part,practice on a 1.5V battery AA, AAA, D etc. touch the leads to each end of the battery, the red lead on the positive end of the battery. The meter should read 1.5V then switch the leads to the opposite ends of the battery, and the meter should read -1.5V.
Checking for a center Hot (or positive plug) is that easy. Learn to use the meter and you will prevent damage from mis-wired plugs. ( and they can come this way from the factory!)
Rex

#17 donnie3

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Posted 29 January 2013 - 08:18 PM

sarry about the terminology i used, im not real savvy on electronics.i got it put together and its working just fine, by the way! all the breeding went just find too, ha, ha, thanks for all the info, donnie

#18 PaulEK

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Posted 30 January 2013 - 01:56 PM

I have a Vixen Super Polaris and use a DD-1 controller. I found out the hard way that Vixen has polarity reversed from the typical outside negative/inside positive. I fried a controller because I didn't think anyone did things this way.

After buying a new controller, I made a dedicated 8-D-cell pack by simply cutting the cord on one, and then crossing and re-attaching the wires. I did this with a cord for my deep-cell battery, too. Since I use batteries for lots of other astro-gear, I then very clearly marked my packs and cords with labels that read 'For SP Only!' and 'NEVER for SP!'

#19 PaulEK

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Posted 30 January 2013 - 02:05 PM

Oh, this lesson has also made me careful to always check the polarity of adapters, cords, and the things that use them. I have a voltmeter (as described above, they are really very easy to use), but I also find that most items have the polarity marked with a little schematic, like the one I've included here (showing the typical polarity).

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