Just when you thought it was safe to go in the water...

[Tukanu]

I get it: When there is a red and a black, the red is hot. When there is a black and a white, the black is hot....except for AC where the white is hot.
Are you with me so far??

I'll admit that everything I know about electrical systems I learned by sticking my tongue in a light socket! Just when I thought I was getting a handle on this electrical thing, along comes a Chinese reading light with two red wires.

reading light.PNG (316.46 KiB) Viewed 2910 times

I'm going to take a wild guess here: When you have two red wires, the first one that goes to the switch is HOT......right??????

[tony.latham]

If it were me, I’d guess with a multimeter.



Tony


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[Tukanu]

I have a meter, but what would be the process? Of course there were no instructions with the light!

[tony.latham]

I’d test for continuity on those two wires with the switch in both positions.

If it’s a DC LED you might play with a nine volt battery and work it out that way.

What’s with the other pigtail?

Tony

[GuitarPhotog]

If it's an LED, you won't hurt it by briefly connecting it backwards. Just try it, with the + to the switched lead first.

<Chas>

[Tukanu]

light2.JPG (28.16 KiB) Viewed 2859 times

The picture makes it look like there are three wires, but there are actually only two...both red!

I touched it to a 9volt and it lights up both ways + and -

[edgeau]

I touched it to a 9volt and it lights up both ways + and -

Well it must be an old fashioned bulb not an LED. It does not matter which way the power flows in a bulb but an LED will only work one way. What is the other connector with the black shrink wrap on it?

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[Tukanu]

It is supposedly a 12v LED reading light from Amazon. Inside the shrink wrap is a small circuit board.

[edgeau]

That circuit board must be doing some smart stuff to give the LED the right polarity regardless of which way you hook it up.

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[Tukanu]

Here are the spec's from Amazon:

Capture.PNG (22.95 KiB) Viewed 2772 times

[Tom&Shelly]

That circuit board must be doing some smart stuff to give the LED the right polarity regardless of which way you hook it up.

Sent from my Pixel 3 using Tapatalk

A full wave rectifier so it will work with 12 vac? Even though it isn't spec'd that way?

Tom

[Tom&Shelly]

I get it: When there is a red and a black, the red is hot. When there is a black and a white, the black is hot....except for AC where the white is hot.
Are you with me so far??

Not the subject of this folder, but for safety's sake--on 120 volt AC house circuits in North America, black is hot and white is neutral.

Tom

[bdosborn]

Interestingly, 12v hot for RVs is black and the ground is white. I've always thought that was a poor choice of colors but they didn't ask me when they picked it.

Bruce

[GTS225]

I get it: When there is a red and a black, the red is hot. When there is a black and a white, the black is hot....except for AC where the white is hot.
Are you with me so far??

For the record; In AC the white is not considered a "hot" wire. It is considered a "grounded conductor". The term refers to a method of "tying down" the AC voltage such that it doesn't exceed the 115 (nominal) to 125 VAC. Without the "grounded conductor", the AC voltage could fluctuate to something quite a bit higher, and damage your equipment. Do not confuse the term with ground wire. The ground wire is not normally a current carrying conductor, while the grounded conductor is a current carrying conductor. It's just that wire colors, set by the Nat'l Electrical Code, are white or natural grey for a current carrying grounded conductor, and green or bare copper for a ground wire. The rest of the colors can be used for your "hot" conductors, with the exception of yellow, that indicates that power is coming from a separate source into that particular enclosure.

Clear as mud, right?

Roger

[H.A.]

Interestingly, 12v hot for RVs is black and the ground is white. I've always thought that was a poor choice of colors but they didn't ask me when they picked it.

NEC calls for grounded conductors to be white. Does not matter if its AC or DC systems.
Said that. I think recently, abundantly marked exceptions are allowed. Probably due to abundance of DC solar.
Most RVs have a shorepower component. Thus, white grounded conductors. White is also standardised in most transportation equipment.