LED Operating Current

Typical LEDs operate on about 3 VDC, and can be dimmed by carefully regulating the current, or via pulse-width modulation.

Since they are diodes, I suppose they would glow when the current is flowing in the proper direction. They'd probably flicker at whatever the AC frequency is.

what are you trying to do? an LED is a diode, DC stuff

As the acronym states, an LED is a diode. A diode will only readily conduct in one direction. The reverse breakdown voltage of every LED I know of is less than the peak voltage of most "wall wort" AC supplies. None can handle the reverse or forward voltage of any power distribution level.

I'm pretty sure that they can survive a PIV of at least 5V. From experience, a back to front LED in a TTL circuit doesn't die...it still works fine when it's turned around and put back in the right way.

It will work fine at say 3 to 5 VAC.

Having a go would be a pretty cheap experiment.

A possible fix, is to place two LEDs, "back to back", assuming of course that there is some form of current limiting in circuit and that maximum PIVs of the LEDs are not ignored.

One LED will light on one half cycle, the other on the reverse half cycle.

It is possible that a series High PIV (normal) diode should be included in each half to make the circuit even more reliable with regard to noise and spikes......though I have never personally actually tried either method......theory only.

A further possible method is to add a tiny full wave rectifier in the circuit (they cost very little nowadays). SMD ones strong enough for a LED, are probably smaller than a second LED!!! Some capacitance may be needed to "get rid of the lumpy DC!" I have not tried this either.

Even though a mains LED with current/voltage control should work if carefully designed, unless a transformer or similar is also in circuit, it may be still be at mains voltage with regard to earth. DANGEROUS!!

Therefore using normal LED mounting hardware may prove very dangerous to any user, as it is usually designed to insulate from less than 5 volts.....not 120VAC or even 230VAC......Use mains rated hardware for say mains lamps, modified to take a LED in some manner....

I would also suggest that using an isolating, voltage reducing transformer for LED illumination, should be recommended......

Put them back to back in series and NOTHING will flow. Parallel them, and you will get a lovely 2 LED light which will be really pretty. I tried this before I posted actually! (used two 10 to 1 transformers to bring it down to a reasonable voltage. The final voltage was NOT 1.5 volts but rather more than twice that. I think that was because of the high impedance (? resistance?) of the diodes.)

Back to back in series and NOTHING will flow was my initial reaction, but AG didn't say in series. He didn't say in parallel either, probably thinking we could work it out for ourselves .

Great! Thanks for the testing too. It was partly only an idea that I played around with in my head sometime ago....

I don't care what anyone says...it's always cool to independently come up with an idea that already exists.

For all we know, you might have been the first.

Thanks, but looking at the good link you posted, its obviously been sometime they have been working on it.....I am just a "Johnny come lately!"......sadly!

Well, I can't blame them for keeping it under wraps.

LEDs are going to be the way to go. It took the massive waste of time and money on CFL bulbs, to really kick it into gear.

I saw a pack of CFLs the other day, for about 50 cents apiece. Problem is, they are absolute garbage.

I've got enough incandescents to last until LEDs are up, running and affordable.

I have bought mains LED replacement lamps from Eachbuyer, that seem to be fantastic price and performance wise, though they have only been installed for about 3 months.....so its early days still.....

They took a few weeks to arrive, which implies that what I ordered was not available in the German warehouse. You take the luck of the draw on that.....

Look here:-

http://www.eachbuyer.com/?gclid=CLjUm7mn9rwCFQcTwwodUQwAHA

The offers with say 4, 6 or 8 lamps at a time, really chop the price down......

Yeah. The prices are slowly coming down here too.

Ultimately, I want to go with dimmable can lighting throughout the house, like we talked about here.

cr4.globalspec.com/thread/72760

I'm going to wait a little longer to take the plunge. I don't even have a flatscreen TV yet.

Till my large & heavy CRT TV is defective, I won't buy one either, although for football & F1 racing......it would be great....

Though I do have a Video projector as well - "Just in case!" But seldom used, except when teaching....

Me too. I've never known anything different, so the picture is just fine.

I'd say that AC driven LEDs, (beyond stings of Christmas lights), will be around soon.

http://www.ledsmagazine.com/articles/2006/05/running-leds-from-an-ac-supply.html

not without a driver, you wont, they will still be diodes

It goes beyond my pay grade, but it looks like it depends on who you talk to.

http://www.allledlighting.com/author.asp?section_id=543&doc_id=560225

I can't tell what these people are doing.

http://www.mouser.com/new/seoulsemiconductor/seoulacrich2/

This looks like a qualifier:

http://www.faqs.org/patents/app/20120091906

sort of, they're still splitting an AC wave to get DC, I meant not a true AC diode, but good searching on your part

I'm always interested in cheap, efficient, anything...as long as it works.

How it works, is secondary, but still interesting.

I'm surprised that they haven't been able to create light by using graphene.

Edit: I spoke too soon.

http://www.understandingnano.com/graphene-light.html

Is this just hype, and still running on DC?

http://www.zdnet.com/blog/gadgetreviews/philips-debuts-worlds-first-ac-powered-white-light-oled-module/17847

don't worry you'll be seeing plenty of graphene based products

Good link, many thanks. My guesswork ideas were nearer fact than even I thought....

yes, no, yes, no, smoke, flash, no...

We use to hook up a tri color LED so

RED = dc+

Green = dc-

Orange = Ac (both fired)

Thats a very useful idea for a simple double indication with either AC or DC! Thanks.

????? Who were you addressing? What are you ranting about?????

On an international Blog, some may not understand what the hell you are talking about......