Are Christmas Lights in Series or Parallel?

[cpwright]

Unfortunately, the bypass wire doesn't actually always burn out to make the rest of the lights work. There is a device called a LightKeeper pro that sends a larger "zap" through the string to encourage the needed bypass wire to burn out. Its saved me a bunch of time figuring out which bulb was bad in a string of lights.

[fbe]

Or you can also DIY with a lighter : https://www.youtube.com/watch?v=7foDiXX-CcE

[vortico]

tl;dr Christmas light bulbs each have a bypass wire which is initially insulated to avoid shorting the filament. If the filament burns out, the new high electric potential burns off the insulation, thus re-completing the circuit for the rest of the bulbs.

[shreyas056]

Actually this is what I hate about such articles, they extrapolate two sentence explanation into huge corpus.

[Rapzid]

I understand the article is about series vs parallel but I'm sort of... Taken aback by the premise setup in the beginning that:

A.) Its hard to find the burnt out bulb(hint its almost always the one with the broken filiment)

B.) You should just throw the strand away

Maybe I'm just too old at 30(?) or I grew up underprivileged because I recall untangling lights and replacing burnt out bulbs well, as far back as I can recall. 7 or so? And throwing the strand away is just wasteful.

I understand there is an article to write but on one hand we have some guy writing about creating a sou-vide oven and on the other someone suggesting burnt out light bulbs are too hard to find. :|

[icebraining]

I agree with you, and I also replaced burnt bulbs as a kid, but nowadays I'm seeing more and more Christmas lights using molded plastic instead of sockets (also, usually with LEDs instead of bulbs), so replacing them is much harder than it used to be.

[_mulder_]

I completely agree.

"in the event of a string of lights going out on your tree, replacing the strand is usually the best option. It’s pretty difficult to find that one bulb that’s causing the problem"

That one sentence sums up most of what is wrong with Christmas, and society, today. I find the "just throw it away if it's broken" attitude really difficult to accept. I would hope everyone reading HN has the self-awareness to consider where their possessions come from and what happens to them when they're thrown away.

[prof_hobart]

It's not always easy to see the broken filament, or at least didn't used to be (I've not really examined many in detail recently).

As a kid in the 80s, I used to work in my dad's hardware shop and people regularly used to bring in lights that didn't work. We had a little test area set up where we would put each bulb in turn to find out which one(s) wouldn't light.

[userbinator]

A truly appropriate article for a site whose name is "wired".

LED sets are usually wired in series too, since they're current-driven devices.

[tmuir]

Although most LED matrices have parallel columns of series LEDs, since they are usually multiplexed at high speed to create the persistence of vision effect.

[mbell]

The answer to this, at least for longer strings, is usually 'both'. You'll usually find several sets of series wired runs connected in parallel and sometimes mid run branches.

[Animats]

The price ratio between comparable LED and incandescent holiday light strings is now between 2 and 2.5 to 1. Incandescent holiday lights probably have about two to three years of life left as a product.

[bradfa]

The white LED strings look very nice and I definitely agree that white incandescent strings have a very short market life left. But the colored LED strings which are sold at Home Depot and similar merchants in the USA have very different colors than the incandescent strings.

I personally find the colored LED strings to have very unpleasing colors compared to incandescents. I've tried a few different "brands" (in quotes as the brand is mostly meaningless afaict) of LED strings and all were not to my liking.

[funion]

Oh interesting, I'd noticed that at some point between my childhood and now, burned out bulbs stopped taking out the entire rest of the light string. I wonder if the bypass wire is a new(ish) development, or if we just had cheap Christmas lights when I was younger.

[virmundi]

You had cheap Christmas lights. We had both. We had the actual bubble lights. Those were more expensive at the time. A bulb could burn out in one of the bubblers and the remaining bubblers would work.

[raldi]

So why aren't the bulbs hooked up in parallel?

[whoopdedo]

Draws too much current. Older strands used to be parallel and were a frequent cause of fires.

LEDs use less power but don't work well in parallel.

[bliker]

Apart from other reasons mentioned. LEDs don’t work well in parallel. Even if you have just 2 of them, one will be bit brighter (drawing more current) than the other.

[chillacy]

Probably to save wire, if you hooked em up in parallel you'd need to send a wire to every bulb from the outlet.

With 10 bulbs at 1 inch spacing, you're wiring 1 + 2 + 3 + ... + 9 + 10 = 55 inches of wire instead of 10

Follows a roughly N^2 law

[francis88]

Curious to know what would happen if 2 or more bulbs broke at the same time?

[guidedlight]

In Engineering, there is no such thing as "at the same time" unless it's a feature of the design.

[swah]

I thought those christmas lights had bee replaced by led strips.

[mindslight]

Piercing blue, icy white, and unfocusing violet aren't so inviting on a cold winter's night.

Black body 4 life.

[_almosnow]

Even LEDs need electricity, and electricity can be delivered to them serially or in parallel too.