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single wire LEDs - why don't they exist? Answered

Because such a thing would totally solve my LED jewelry problems. I'd love to able to just solder an LED onto a necklace chain without needing to slice the chain. So why can't I? Curious.



Hi, I read thru most of this thread and I think you're not seeing how an led does it's thing.

An led is like a one way valve. electrical current doesn't just go in and change into light, like gas might go into an automobile...it goes by and excites the insides, which in turn give off light, more like the way a water wheel works...the water is the same when it goes in as it is when it leaves...the only difference is its potential energy is lower on the way out after it has done some work. It needs two terminals to work because one is used as the inlet and the other as the outlet...light is just a byproduct of the flow thru the led.

I understand that. Where I got confused is why after the current goes through the LED that it needs to go back to the battery. Like if the battery is a glacier in your analogy that melts into the water which goes through the wheel. Why does the water need to then go all the way down the river and eventually back to the glacier and be refrozen and melted again? Why not just pipe it around and right back into the wheel? I guess my main mistake in describing what I mean was to call it a "single wire" LED. There's still the outgoing wire in my hypothetical, but it's build onto the LED itself, returning the current back to the in side (rather than that wire going back to the battery). Next time I ask a question, I should just draw a picture. I'm terrible at describing things.

Okay, I did draw a picture. It would seem I'm equally bad at drawing as describing. But anyway, this is my hypothetical LED.


lol, not as bad as many I've seen...

hmm...you're still missing something...people think of electrons like a fluid...that is, it makes a useful visualization tool, but what many fail to understand is that with electrons, you can't just strip them off the metal...they are conserved...so if they flow thru something, from somewhere, there needs to be a path to replace the ones that were lost (in this case, from the battery)

SO in your picture, the poor sot who has to trudge all the electrons back to the battery (near the "B" in battery) from the led is missing.

understood? they can't just go back along the same path., or they'd interfere with the ones going down the wire to the led.

they can't just go back along the same path., or they'd interfere with the ones going down the wire to the led.

That's why my imaginary LED has two in wires. Although okay, I'm seeing the flaw in that. So remove the two ins on the LED and put a resister there with two ins on it instead!

Or would we need to add a second battery into the mix as well, making it out-wire/battery2/wire/second-in on the resister? But I think I'm going to just give up on my hypothetical, because by the time I add enough parts to make it work, it'll likely be a bulky mess that's much more annoying than needing a second wire.

And I think I'm getting it now, thanks. So in my earlier picture (the one of the battery/LED/second battery set up), that's working because there's still the poor sot doing the trudging, so the electrons still have somewhere to go. Although it's a bad idea because they have no way to leave that second battery.

Somebody told me to just use a capacitor, and then I wouldn't need to connect back to the battery. So, can anybody tell me how a capacitor works? Any chance there's a guide with pictures?


8 years ago

You can connect LEDs together in series (although it's not the preferred approach):

+ --O---O---O---O--- -

But the more LEDs, the greater the voltage required. After just a few LEDs there would be a shock hazard...

You need a complete circuit - current must flow through the LED to make it work.

Yeah, but it only goes one way, doesn't it? So I guess I was more wondering why you need a second wire going back to the other side of your battery as opposed to like a wire built onto the LED itself that goes back into the LED on the other side. And wow, I just did a terrible job of describing what the heck I mean. Ya know, a loopy thingy. LOL! *facepalm*

I think what you mean is why aren't they configured like resistors, with the legs existing on the same line, rather than being parallel to each other, right?

why aren't they configured like resistors, with the legs existing on the same line, rather than being parallel to each other

But actually, that is a good question. Why?

Actually, no, and I'm not sure how to describe what I mean either. It's kind of a hypothetical design of a new LED that doesn't exist, and I'm wondering why it wouldn't work. I'm an LED newbie. I'm confused about the current and completing the circuit. I'm assuming the current only goes through the LED in one direction, so please correct me if I'm wrong about that. Let me try to describe my hypothetical LED again. Let's say we have a regular surface mount LED. We attach a wire to one side of a battery and connect it to one side of the LED. Now in the real world, we need to take another wire and connect it to the other side of the LED and to the other side of the battery. This completes the circuit, we've basically made a loop. But what if we don't connect the second wire to the battery, and instead we loop it from side two of the LED back to side one? I know you can't do this with a regular LED. My non-existent theory LED we'll assume is designed for this purpose, having two connections on the first side and one on the second. Does that make any sense at all? I want to what would happen with the current and the completion of the circuit in this situation. And completely not what I just described (because that doesn't actually exist), but I'm attaching a picture of my lit LED where the wires never connect back to a common point. So this would indicate that it's not a one-way circuit loop, wouldn't it? I'm totally confused.


You could if you used your chain as one side of the circuit. But then, you'd need another wire for the other side (unless you used a LOT of LEDs and just soldered the legs together ;-)