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TOPIC: Correct polarity of foreign lights

Correct polarity of foreign lights 3 years 10 months ago #21511

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A question I had a while ago but found out the hard way (Resulting in a blown charger).

However I've just been asked by someone else too so thought it was worthy of a post.

When using a UK adaptor, if the wire comes out of the bottom of the charger, it needs to go to the left. Most foreign stuff is protected against reverse polarity, but it would seem a lot are not.


2014-01-0908.31.05.jpg
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Last Edit: 3 years 10 months ago by Sweetie.
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Correct polarity of foreign lights 3 years 10 months ago #21519

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The direction of the charger should have no bearing as the outlet delivers AC...
AC changes polarity according to frequency, in the UK that is 50 Htz and therefore the polarity alternates 50 times a second. It is only the DC side that would matter and it will put out the correct polarity DC regardless which way around the AC side is connected...
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Correct polarity of foreign lights 3 years 10 months ago #21520

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All I know is I bought 2 lights exactly the same, the 1st charger worked for 5-10 seconds then fizzed a bit, then the LED went out, I tried the 2nd charger the other way around (as per the pic above) And it's worked fine.

Possibly just a duff charger then? :(
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Correct polarity of foreign lights 3 years 10 months ago #21521

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Possibly a duff charger. There is no polarity on AC, that is why it is called Live and Neutral rather than Positive and Negative.

There is only a difference between Live and Neutral because one side of the circuit (Neutral) is tied to Earth so it won't bite you as you are at Earth potential.

If the charger needed an Earth connection to function (Functional Earth) then there 'might' potentially be an issue as the potential between 'Live and Earth' and 'Neutral and Earth' might not be what the circuit expected (or was designed for). however, Functional Earth's are extremely rare in electrical appliances and only in use in some Telecoms equipment. If the charger is reversible then there won't be an Earth connection (as the third pin would stop the charger from being reversible) so as far as it is concerned the AC is just alternating between the two conductors and won't make any difference...
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Correct polarity of foreign lights 3 years 10 months ago #21522

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Sweetie wrote:
All I know is I bought 2 lights exactly the same, the 1st charger worked for 5-10 seconds then fizzed a bit, then the LED went out, I tried the 2nd charger the other way around (as per the pic above) And it's worked fine.

Possibly just a duff charger then? :(


I had one like that ... except that, as well as fizzing, it began "burning" and emitting smoke. There would have been a fire had I not been there to witness it :unsure: :unsure: :unsure:

(and it was recent)

(and it was bought in the UK)

(and it was probably made in China)
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Correct polarity of foreign lights 3 years 10 months ago #21525

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duff electrolytic capacitor normall if theres a nice load of white smoke.

Yes no such thing as negative/positive polarity problems with ac. Alternating Current (AC) swapping from flowing in each direction 50 times a second (ish) in the Uk.

It ha's to be ac for a transformer to function with will drop the voltage in proportion to the number of windings, the out put of the transformer is still ac but at a lower voltage. It'll then be rectified (usually using 4 diodes is a bridge so now it becomes a 'lumpy' voltage (think of of a sine Wave, the negative troughs have been flipped upside down so everythings now above the line - but still lumpy!) So its now all flowing in the same direction so negative and positive voltage becomes relevant after the rectifier. It'll then normally have a decent sized capacitor which is kind of like a buffer which will smooth out the lumps and bumps and give something a bit more like a steady DC voltage. It'll then normally have some kind of voltage regulator or current control depending what its being used for (i.e. precisely controlled voltage source or current limited battery charger etc).
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Correct polarity of foreign lights 3 years 10 months ago #21527

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I had a load of Chinese plugs with some cctv cameras, most of them didn't work. The problem was crap soldering, i opened them up and soldered the wires back on the pins and they've been no trouble since
oh, what fresh hell is this?
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Correct polarity of foreign lights 3 years 10 months ago #21528

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That piece of shit us-uk adaptor is not fused. Please change it before bad shit happens.
You want me to go down *there*? On a bloody *rope*?
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Correct polarity of foreign lights 3 years 10 months ago #21535

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The shit soldering is the fuse ;-)
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