Positive or negitive for 12v 2 pin plug plug

Submitted: Sunday, Feb 17, 2008 at 23:42

Member - LOS BUSH

Which terminal is the Negitive for the 2 pin 12v plug that looks similar to the 3 pin x 240v plug on an extenion cord.Is it the one that is vertical and is in a similar position as an extenion cord or the horizontal terminal that looks similar to a _ or negitive sign.Is there a standard or some general convention
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AnswerID: 288083   Submitted: Monday, Feb 18, 2008 at 00:20

disco driver replied:

Hi,
AFAIK there is no set system although most I know use the horizontal pin or socket as the positive(+) and therefore the vertical as the negative(-).

It depends on who wires it into the vehicle system.

When I wire them on my vehicles I usually wire back direct to the battery terminals and fit suitable fuses (and switches if required) to the positive cables.

Others may do it differently.

Disco.
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Reply 1 of 16
FollowupID: 553350   Submitted: Monday, Feb 18, 2008 at 08:26

Mainey (wa) posted:

Yes, there IS a set system, and Disco as you say the top or horizontal is the 'positive' and the lower or vertical is the 'negative'

Mainey . . .
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FollowupID: 553580   Submitted: Tuesday, Feb 19, 2008 at 13:27

Nomadic Navara posted:

It's all very well to talk about vertical and horizontal pins, but which way do you mount the plug?

The old DCA standard was to mount the 2 pins in a horizontal line and the one that looks like a negative symbol is the -ve.

The old OTC standard was was to mount the two pins in a vertical line and again the one that looks like a negative symbol is the -ve.

That is how I would expect them to be wired - according to the way you mount them.

PeterD
PeterD
Retired radio and electronics technician
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AnswerID: 288085   Submitted: Monday, Feb 18, 2008 at 00:31

Derek from Affordable Batteries & Radiators replied:

Vertical is (-) when I use them.
ABR - SIDEWINDER
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Reply 2 of 16
FollowupID: 553337   Submitted: Monday, Feb 18, 2008 at 00:45

Member - LOS BUSH posted:

Disco ,Derek Thankyou for your reply - Los


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AnswerID: 288097   Submitted: Monday, Feb 18, 2008 at 07:26

Outnabout David (SA) replied:

Think you will need to check further for yourself.
I had a camper trailer that came wired with + vertical and - was horizontal
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Reply 3 of 16
AnswerID: 288099   Submitted: Monday, Feb 18, 2008 at 07:54

Dave from P7OFFROAD Accredited Driver Training replied:

The 'convention' is for positive to be on top! Negative under it!

Assuming that you recognise it as a T plug and place it that way!


Good choice BTW!
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Reply 4 of 16
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AnswerID: 288103   Submitted: Monday, Feb 18, 2008 at 08:50

Member - bungarra (WA) replied:

as others have posted...the "top" is positive

a simple way of remembering is the following example I tell people who ask me

when viewing the plug as a "T"

The Horizontal is positive, the HOT end H = H
The vertical is naturally negative as in a 240v 3 pin plug

as others have said..... always fuse your lines, or at least every accesory, as under Murphys law someone, somewhere will get it wrong and you cannot guarantee that your device or leads may get used or swapped one day by some innocent soul !
Life is a journey, it is not how we fall down, it is how we get up.
VKS 1341
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Reply 5 of 16
AnswerID: 288105   Submitted: Monday, Feb 18, 2008 at 09:04

Tony MD replied:

There is no standard. Always check polarity first.
Wicen Victoria
use the top horizontal pin as negative. The link also states that it is believed that Wicen NSW uses the top horizontal pin as positive; this as I first learnt as an apprentice electrician 30 odd years ago!
WICEN is the Wireless Institute Civil Emergency Network.
Cheers, Tony
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Reply 6 of 16
FollowupID: 553360   Submitted: Monday, Feb 18, 2008 at 09:22

Mainey (wa) posted:

How things change
I back Derek's and others posts that the top is the (+) terminal connection in a *12v power* system.

Mainey . . .
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AnswerID: 288117   Submitted: Monday, Feb 18, 2008 at 10:13

Member - Kiwi Kia replied:

In my electrical circles it has been convention to use the horizontal as negative. Easy to remember as horizontal ----- looks the same as negative --.

As has already been mentioned this is convention only.
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Reply 7 of 16
FollowupID: 553367   Submitted: Monday, Feb 18, 2008 at 10:18

Member - Kiwi Kia posted:

I should also have said that I am refering to the plugs that are similar in size and shape (other then pins) to the 230 V plugs as this is what the original question refered to. On the small line conectors as found on motor vehicle wiring looms its the other way around.
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AnswerID: 288125   Submitted: Monday, Feb 18, 2008 at 11:27

Member - Mike DID replied:

Where there are two ways of doing something, there will be two "standards" e.g. which side of the road to drive on - unless there is a body to publish a firm standard.

That never happened for the T plug.

Fortunately the other moderrn DC connectors don't have that problem -
- Cigarette Lighter - centre always positive
- Merrit Socket - centre always positive
- Grey 50 and 175 amp Anderson SB - polarity s marked on the connector.
- Red/Black 30 amp Anderson Powerpole - red is positive.

The T connector is falling out of favour, not just because of the problem of reverse polarity damage, so you would be better off changing to one of the more modern standard connectors.
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Reply 8 of 16
AnswerID: 288126   Submitted: Monday, Feb 18, 2008 at 11:28

Gone Bush (WA) replied:

Don't confuse poor old LOS.

Tell him it's vertical for negative and it's referred to as a T (tee) plug.

All he has to do then is turn all his plugs up the right way and re-wire them.

cheers LOS.
I'm glad I ain't too scared to be lazy
- Augustus McCrae
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Reply 9 of 16
FollowupID: 553385   Submitted: Monday, Feb 18, 2008 at 11:55

Member - LOS BUSH posted:

Listen Bush,enough of the "poor old Los" stuff. I thought you could not resist the temptation to place a post.You told me I was the only one on earth that had a horizontal Negative.It is obvious that many are unsure and do what suits them as there is no standard, only a flimsy convention Why would I turn the plugs around I am happy the way they are. Los
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FollowupID: 553454   Submitted: Monday, Feb 18, 2008 at 18:39

Gone Bush (WA) posted:

LOS it seems like half of Australia wires these plugs like you do and half like I do.

I learn something every day. Sorry to sound like a smartypants it sure wasn't meant that way. I'll have to use "lol" a lot more (lol = lots of laughs).

When it's time to re-wire your Effie we'll talk about Arrid/Merit plugs and sockets. They are very good.

cheers

I'm glad I ain't too scared to be lazy
- Augustus McCrae
Lifetime Member: My Profile  My Blog  Send Message
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FollowupID: 553467   Submitted: Monday, Feb 18, 2008 at 20:15

Member - LOS BUSH posted:

Thank you Bushy We seem tohave more in common than our surname
see you 'round Los Bush
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AnswerID: 288131   Submitted: Monday, Feb 18, 2008 at 12:03

Member - Mike DID replied:

There other reason that there are two "standards" for wiring these plugs, is because there are two ways of wiring them, and for EACH, it's obvious that it's the logical way to wire it -

T - the vertical is earthed, because it looks like the Earth on an Australian Mains socket.

Inverted T - the horizontal is earthed, because it looks like the earth and like a Minus sign.
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Reply 10 of 16
FollowupID: 553390   Submitted: Monday, Feb 18, 2008 at 12:40

Member - LOS BUSH posted:

G'day Mike, Thanks to you and others for their interest, LOS
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AnswerID: 288147   Submitted: Monday, Feb 18, 2008 at 15:00

res.q.guy replied:

We (family and friends) have always wired the horrizontal (or top part of the T) as neg and the vertical as Pos.
Neil
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Reply 11 of 16
AnswerID: 288176   Submitted: Monday, Feb 18, 2008 at 18:11

Dunaruna replied:

I agree with the majority, I alway use the vertical as the negative.

Just to clear up something though, there is no official Australian standard for this type of plug.
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Reply 12 of 16
FollowupID: 553491   Submitted: Monday, Feb 18, 2008 at 21:18

Member - Kiwi Kia posted:

Dunaruna, Just to keep the argument (discussion) going :-)) What makes you think you are in the majority ?

I would also point out that the 'T' plug used to be common in electrical equipment to indicate 110 V ac and not 230 V ac !
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FollowupID: 553502   Submitted: Monday, Feb 18, 2008 at 21:45

V8 Troopie posted:

You may confuse it with the plug that has two parallel flat pins as used in the American system.

The 'T' plug is a designated LOW VOLTAGE plug and low voltage only goes up to 50V.

Me thinks its illegal to use these 'T' plugs for 110VAC and I have never seen them used for that.

If you need to distinguish 110V from 240V it may be best to use the plug with a round earth pin and two flat, angled pins for active and neutral.
Klaus
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FollowupID: 553504   Submitted: Monday, Feb 18, 2008 at 21:54

Dunaruna posted:

Kiwi, 11 people posted an opinion as to which slot should be negative. 4 said the horizontal, 7 said the vertical. That's a majority, I was agreeing with the majority.
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FollowupID: 553513   Submitted: Monday, Feb 18, 2008 at 22:14

Member - Kiwi Kia posted:

V8 Troopie, Sorry, I should have said American 110 V and no, I am not confusing it with the flat parallel pin plugs.
Those 'T' plugs were very common on 110 V transformers about 30 years ago.

Also, you are a bit behind the times. 230 V IS low voltage (anything below 400 V). Part of the change is to do with allowing non-registered people to work on 110 V (fork lifts etc). 110 V is also commonly used on European machinery and is derived from 110 volt centre tapped transformers giving a swing voltage of 55 volts each side. The worst voltage you can get to earth is then only 55 V. Great for safety & control circuits.
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FollowupID: 553585   Submitted: Tuesday, Feb 19, 2008 at 13:56

Mike Harding posted:

>The 'T' plug is a designated LOW VOLTAGE plug and low voltage >only goes up to 50V.

I suspect you're thinking of "Extra low voltage" which is below 50V AC or 120V DC.

Low voltage is above ELV and below 1000V AC or 1500V DC.

A quick look suggests Clipsal rates these plugs/sockets at 32V (they don't say AC or DC but I suspect it's DC).

Mike Harding
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AnswerID: 288249   Submitted: Tuesday, Feb 19, 2008 at 00:22

Muzzgit [WA] replied:

My T plugs were wired up by an auto leccy and the top is positive
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Reply 13 of 16
FollowupID: 553586   Submitted: Tuesday, Feb 19, 2008 at 13:58

Member - Mike DID posted:

Which just goes to show there isn't even an agreed convention as to whether the top or the bottom will be positive !


"Tony MD replied:
There is no standard. Always check polarity first. Wicen Victoria use the top horizontal pin as negative "


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AnswerID: 288257   Submitted: Tuesday, Feb 19, 2008 at 08:20

obee replied:

I would have to choose the the same as the honda gennie or I could end up blowing fuses or worse.

Owen
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Reply 14 of 16
FollowupID: 553661   Submitted: Tuesday, Feb 19, 2008 at 20:19

Member - Mike DID posted:

On the Kipor Generator it's mounted as an Inverted-T (I over -) with the lower Minus as Negative.
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AnswerID: 288296   Submitted: Tuesday, Feb 19, 2008 at 13:41

Member - Mike DID replied:

Keep in mind also that there are TWO SIZES of T-plugs.

The ones that have been used in Australia for decades have a 15mm gap between the pins.

The ones that provide the battery charging output (unfortunately mis-labelled as DC Out) have a 6mm gap between the pins.
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Reply 15 of 16
FollowupID: 553582   Submitted: Tuesday, Feb 19, 2008 at 13:48

Member - Mike DID posted:

3rd sentence should read -

The ones that provide the battery charging output (unfortunately mis-labelled as DC Out) from portable generators have a 6mm gap between the pins.
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AnswerID: 288298   Submitted: Tuesday, Feb 19, 2008 at 14:04

Shaker replied:

Has anybody put a multi-meter on a generator 12v output socket, surely that would give more than a clue!
Anyone who lives within their means ..... suffers from a lack of imagination!
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Reply 16 of 16