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MG Midget and Sprite Technical - LEDs - leccy question

are LEDs +ve and -ve sensitive? I just soldered in a new number plate lamp on the trailer and it doesn't work, even though the test lamp (old bulb and wire) works when clipped to the same wires!
David Smith

David...the "D" stands for diode..which is a semiconductor device which allows current to flow in one direction only..so my guess is that they ARE "handed"...
David Cox

yes - expensive ones have electronics to make them insensitive, but cheap ones dont
timmyk

At least you shouldn't damage them by connecting in reverse as the reverse breakdown voltage will be far higher than the forward voltage.
David Billington

Yes, they only conduct in one direction.
Bill Bretherton

They should also have some kind of marking for the plus end, a bump or high spot, a + or some such. And depending on the size of the LED, these may be very small.
Martin

Ditto the above. I replaced the interior lamps in my Fiesta with LEDs, and found that they are indeed polarized. And yes, there should be a little bump or something to identify the positive.

-:G:-
Gryf Ketcherside

I don't know about LED bulbs, but 'traditional' LEDs had a flat on the cathode end (-ve).
Dave O'Neill 2

Thanks guys. These were number plate lamp units with prewired tails, just a red & black. Think it's the trailer that has the non-standard wire colour code. Swapped 'em round, re-soldered and heatshrink, all working fine now.
David Smith

Possibly not David, ISTR some rather expensive 12v florescent tube lights I fitted to the boat many years ago and black tails were in fact positive in the far eastern wiring when I actually checked the diagram (having blown one of the new units !)

R.
richard b

This thread was discussed between 31/01/2018 and 01/02/2018

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