Is it possible to dim LED christmas lights?

That depends on how they are wired.

If a transformer is used, then you could use an adjustable transformer (Variac) to reduce the voltage to the transformer.

If a transformer is not used, you could use a standard light dimmer - check the combined wattage of your lights to get the proper capacity dimmer.

Note that standard light dimmers will NOT work with transformer powered lights (or not for very long...

John

You could cycle each set for lower power and a twinkle effect.

I know they are 4V per bulb. If I take out one bulb, then all of them go out so I assume they are in series and not in parallel. I can't see any transformer.

LED's are binary devices - either ON or OFF. They cannot be dimmed in the usual sense. Their average output can be changed by the duty cycle. If they are switched on & off fast enough, the eye will not see them flickering, but will see a lower average output. I.e., dimmer.

A 60 Hz cycle would be flicker-free and there is a convenient 60 Hz signal source 8-). There may or may not be a commercially available black box to do this. It would be trivial for an electronics hobbiest, but my guess is that you are not one.

HTH, Bob

Hobby, hobbier, hobbiest. ITYM hobbyist, but you may well be right, he doesn't seem to be the hobbiest of them all!

Cheers, Pete.

quote 'LED's are binary devices - either ON or OFF'

This is rubbish.

The light output from a light emitting diode is a function of the current passing through it. Most devices will show a wide variation of brightness from say 1 to 20 mA.

Another Bob

I'm not one to usually nitpick on that sort of thing, but the error over "hobbyist" has always jumped out at me.

I suppose if I could figure out why it's a common error, I might be more understanding. But I can't figure out why the mistake is made, so it somehow seems worse.

Michael

Bob Minchin wrote: ...

OK, so how would the OP go about dimming his LEDs? Bob

I don't know why, either. It just came out. If I HAD thought about it, I would have used "hobbyist", probably. Maybe "hobbiest" is used (incorrectly) so much that it has imprinted itself on me. Or maybe I was just blindly converting the sound.

Sorry. It won't happen again. I am annoyed by that sort of thing, too. But let's not turn this thread into "spelling errors that annoy me".

Bob

"DeanB" schreef in bericht news: snipped-for-privacy@l39g2000cwd.googlegroups.com...

Hmm... Nine hundred LEDs in series with 4V/LED will require 3.6kV. Unlikely.

How do you now they are LEDs anyway? If they are directly connected to the mains - so no transformer or other black box in between - I assume them to be incandescent bulbs.

petrus bitbyter

Shouldn't have sent the correction, sorry. Thing is, it didn't annoy me, I just thought it was amusing and I was in a silly mood. Note to self: Do NOT post while drunk... Do NOT post while drunk...

Cheers, Pete.

Calculate the power consumed by your lights and, being careful not to exceed the rating of the device, get one of these.

For what it's worth, I bought some LED Christmas lights (they certainly don't get warm) two years ago, and there's no transformer. I assume they use some sort of series and parallel combination. Though I've not wanted to sacrifice the string to figure out what's going on.

I suspect it's not a single string of 900 lights, but a number of separate strings, coupled from one to the other in the same way that traditional incandescent Christmas tree lights went, a plug at one end and an outlet at the other to plug in the next string. That way you don't have to bring each string down to the outlet, but each individual string is seeing 120VAC.

Michael

No no no. I was replying to Michael Black, who was annoyed. Your post was clever and amusing itself and not offending (oh,no is that the right word?). I would try drinking while posting, but I think that my posts would become more error-filled rather than more clever.

Bob

So you may have thirty LEDs in a string and thirty strings in parallel. Which seems to make sense but how to explain that when you remove one bulb all of them go out? Besides, when they are real LEDs, there should be some rectifiing mechanism as a LED - one LED - cannot handle AC.

*If* they are real LEDs *and* there are no coils *and* no transformers *and* no electronics but rectifiers *then* you may use an ordinary dimmer. But as long as you are not sure about the components and the circuit it's gambling with 900 small lights at risk.

petrus bitbyter

They are 60 bulbs on an individual string. I guess in the wire there are 2 pairs of wires, giving 110 V over a set of 30 bulbs, or just under 4V each in series, which is why they all go out (actually only half of the string goes out).

I will try a dimmer (I have one like that) and give and update tonight. Oooh, the tension is killing you all, I know! I'll be sure to post before midnight, then you will be able to get some sleep without being concerned:)

Hell, I've sent messages when drinking - no big deal. "My" problem came when I sent a message and was so damned tired, even the toothpicks were snapping under pressure to hold my eyes open. I was replying to one person - kept dozing off and when "trying" to wake up - in my dreamy state - thought I was writing to a girl friend and well - sent some stuff (words) to someone - they "shouldn't" have seen. That was downright embarassing. I bet they got one hell of a good laugh!

No, I'm not annoyed.

It is just something that I can remember being misspelled thirty years ago when I first came across the term, and I do wonder why it so often is spelled the wrong way.

Michael

current

brightness

From other replies there are 900 LEDs. These must be connected in some form of series/parallel network either connected to rectified mains or a lower voltage transformer &rectifier arrangement - probably the latter if in UK to meet safety regulations. Dunno about the other side of the pond with your low voltage mains supplies. Either way putting longer chains in series will drop the current nicely by

1/2 1/3,1/4 etc. Bob In UK