Are LED lights polarity sensitive?

[centerline]

I bought and installed a set of seachoice LED Nav lights for the bow and they dont come on.... i did not check which wire was ground and which was positive as I thought I knew and hooked them up accordingly, but now that they dont come on, im questioning if I hooked them up backwards and if the polarity would make any difference with an LED light....
does anyone know if the polarity makes a difference?

 

[MrUnix]

Yes - it's a diode.. polarity makes a difference.

Cheers,
Brad

 

[Squidd]

Yes, I put in 5 leds in boat's saloon...Direct replacement screw in...

Three came on but two did not...I had to rewire the light fixture as the +/- feed wires already were correct colors..

 

[tkanzler]

Diodes are essentially electronic check valves, passing current in one direction only (in their simplest form). LEDs emit light while passing current, but they're still diodes. Polarity matters.

In fact, folks often use a single pair of wires to run an anchor light or masthead (steaming) light by wiring the LEDs opposite each other in polarity, then switching the polarity of the wiring. One way gives you masthead, the other gives you the anchor light. Or red and white cabin lights, again by reversing the polarity of the supply wiring.

 

[Jackdaw]

One on their thing to keep on mind... Althought individual LEDs are diodes, many of the new drop-in replacment bulb parts have on-board regulation that correct for inverted polarity.

 

[Don12364]

And:-

The LEDs may have additional on board control circuitry. This will be polarity sensitive too.
In fact there is no assurance that just once connected in reverse polarity for just 1 millisecond will not have permanently destroyed the devices.

NEVER just connect something to a source of power without making absolutely certain that you know which wire of the supply is + and which is -.

Also NEVER just connect up unless you know which wire of the device needs to be + and which -.

From here onwards just about everything electrical/electronic for boats is going to be polarity sensitive or run from AC.
You have been warned.


Don't think in terms of 'hot' and ground', think + and - because, although convention says - would be ground, there is gusrantee that this will be the case.

 

[walt]

As mentioned, almost any LED light you can buy now is really more of a small switching power supply that drives LED’s with its output.

So the two wires you are hooking up really go to a switching power supply - not directly to LED's.

Unless the manufactures says you can, I would not hook up any switching power supply (in this case an LED light assembly) to the wrong polarity. Often they have some tolerance to being hooked up backwards by design as it keeps the warranty return lower but I personally wouldn’t do it..

In fact, folks often use a single pair of wires to run an anchor light or masthead (steaming) light by wiring the LEDs opposite each other in polarity, then switching the polarity of the wiring. One way gives you masthead, the other gives you the anchor light. Or red and white cabin lights, again by reversing the polarity of the supply wiring.

If you do this with modern LED lights, you would be really hooking up switching power supplies (which may or may not be tolerant to being hooked up backwards). This is a lot different that just hooking up simple diodes. You could still do this trick with incandescent light bulbs, you just needed to add an external diode to the simple circuit. In the case of a modern switching circuit LED, you should either check to make sure the manufacture says you can hook it up backwards (to near 15 volts) or just add an external diode like you had to do with the incandescent light bulb.

 

[rgranger]

Don't forget to check the simple stuff first. Are your battery leads clean? Are the fuses in your switch panel still in working order?

 

[centerline]

Don't forget to check the simple stuff first. Are your battery leads clean? Are the fuses in your switch panel still in working order?

yea.... the incandescent lights worked about 15 minutes before the change over.... ill get the polarity switched sometime today.

Thanks everyone for all the help....

 

[kenn]

In fact, folks often use a single pair of wires to run an anchor light or masthead (steaming) light by wiring the LEDs opposite each other in polarity, then switching the polarity of the wiring. One way gives you masthead, the other gives you the anchor light. Or red and white cabin lights, again by reversing the polarity of the supply wiring.

... that's clever! Never thought about that.

 

[tkanzler]

... that's clever! Never thought about that.

But in light of what others have warned about above, do go into it with open eyes. Except for incandescents with diodes to do the same thing. Or LEDs, but with diodes to protect them.

Personally, I'd be more inclined to just replace or add another cable to get what I need. I probably shouldn't have even brought it up.