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A look at the internal construction of a common type of low voltage LED filament that is often used to give the effect of a long coiled filament in decorative lamps.
The 300mm (12") filaments have an illuminated section of about 285mm (11") with 200 LEDs in parallel along the length, running at around 3V. This makes them very easy to power with batteries or a USB power supply, using a couple of 10 ohm resistors in series.
In a dim room they can be run at extremely low current to get a strong visible line of colour. Literally just a few milliamps.
Here's a link to the Aliexpress seller, but be careful to check the price before ordering, and if they start to price gouge then look elsewhere.
The 300mm versions currently cost about £7 for five including shipping.
There are other sellers with more expensive listings. I'm not sure if the filaments they are selling are a higher spec or if it's the same ones.
If using these in a way that will allow lots of flexing, then I'd recommend reinforcing the ends with a short piece of 2.5mm heatshrink for strain relief. If using in a costume then make sure they can be removed and replaced easily.
A link to the video that inspired me to try some of the filaments out:-
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Flexible led filaments, i thought i'd get some and strip one of them apart and take a look. It turns out they're quite hard to strip apart, i was hoping i was going to be able to peel some of the silicon off to reveal the circuit board, but, as it happens, uh any attempt to actually scrape it very gently. The knife ended up just cutting the circuit board and then, when i cut bits and uh off, i put them in various solvents to hoping that i could dissolve the silicone and reveal the circuit board. No luck, but that's okay, because what i actually did in the end was i illuminated a controlled intensity and i stuck a magnifying glass glass over it and duded it down and then created a graphical representation which i will come to in a moment.

It's a very interesting construction, so the reason i got these is because another youtuber who makes models had made a model of a neon sign and they'd use this. So it's a scale model, but it had this very sharp outline of this stuff and the stuff operates at three volts per section. So basic at four sections here and at the moment it's at 12 volts and it's passing 200 milliamps. The 200 milliamps equates to just one milliamp per led in here, because there are 200 leds in each section of this.

I worked out that in the 285 millimeters that is lit up that's about 11 inch. There are 200 leds, so roughly 7 per 10 millimeter. The circuit board inside appears to be 1.5 millimeter wide and then it's coated in the phosphor. Now it's worth mentioning the seller.

I got these from on. Aliexpress is selling what appear to be slight rejects, and it's not an issue for people like us that are just experimenting with them. But if you look along it and you're not really going to see it because uh, you certainly wouldn't see in the distance, but i can see right now. There are occasionally dark bits along it and it's not because the leds are out.

It looks as though the leds have flipped up sideways and are actually projecting light out the side instead and that's viable for the way they're soldered on. So let me bring in a doodle and show you the construction of this. I shall also zoom down slightly zooming down, so the circuit board is a very thin flexible circuit board, very delicate and it has a pad on each end and then a series of uh pairs of pads with what appear to be flip chips. Flip chips are leds that basically have little solder pads on them the bare chip itself, so it's almost like a surface mount led, but there is no package.

It is just the bare led it's the way a lot of stuff has gone and what it means is that they can apply probably a continuous process. They can apply a solder paste onto these little pads. They can use a machine that, and goodness knows how it does it, because they're tiny that picks and places the leds on and then it will take them into a reflow oven. It will heat the soil drop and it will flow on and soda them.

That's where i think some of these little leds are sitting across like that to think as the sodas they're flipping up in their end, like that, because the light distinctly shines out the side for some of them and the arrangement they've got you've got the positive end And the negative end, they have the large pad thermal isolation going over to the first led and then they've got a bus going up one side that connects to the positive all the leds and then the other side is a bus that goes down all the negatives And that means that, theoretically, this led here has the same sort of circuit resistance as the led in the middle, because the tracks the same length but in reality, and i'm not sure why this is the green - is visibly brighter at one end. Uh at both ends. Actually, but duller in the middle, as is the blue, i'm not sure why the current isn't shearing. Equally, i wonder if that's part of the degradation, the middle with the flowing process, i'm not really sure but uh.

This arrangement means that these leds are these whole filaments. Just operate at three volts because all the leds are effectively in parallel. Let me bring in a notepad and doodle. Oh there's, another pen.

I should use that one. So the construction is this: they have the circuit board with the little tiny chips mounted on it, and then they coat it with a phosphor loaded gel and the other side is coated with slightly less phosphor coated gel it's more translucent the other side and any light That gets bounced off the top also goes through the circuit board and comes through the bottom to terminate onto the strip at the end, has a crimp put on it, a little crimp that just basically goes under it like this and folds around, and bites into that Copper pad at the end and that's the connection. Then they seem to secure and place the little blob of silicone and then put that sort of the phospholoaded silicone on it. It's very neat the crimp itself when it comes off the end, has a little tag.

That comes off like that. The positive one has a hole through it. Just in case you get some of these there's a one of the tags is no hole. It's a negative one of the tags as a whole.

It's positive just for reference, that's how to identify them. The colors uh you've got the sort of warm white. It's goldeny white you've got the green, the blue and the pink. This is red, but red doesn't work that well, it's nowhere near as bright as the other colors, but that's because the red doesn't really want too much blue and blue is the main stimulating led that stimulates the phosphorus.

So they have to use quite a thick layer of phosphor to get the red, but actually hide the blue from say otherwise, you'd end up with a pinky color. So this one is a fairly dark red. I should show you it shouldn't. I i should one moment please and back again: uh here is the red and again it's got a real hot spot at the end, but dim in the middle.

I'm not sure why that is, but you can also see the irregularity of the leds in this stuff. It's really pretty visible. I shall zoom down a bit, so you can marvel at the irregularity hi. It was cheap.

I knew what i was getting, i'm just glad that all the leds are lit, but it's notable that the ones uh that, where there's a gap, it's you twist it slightly and uh. It seems like they're just pointing light out the side very strange. I'm not sure why that is if they've just flipped up or it's something else and the red, though not as bright as others. It's worth mentioning that uh, you run these at three volts and uh, i would say one milliamp per led is ample, i'm not sure what they're rated, but certainly that would equate to three volts 300 milliamp 200 milliamp.

That would be 0.6 watts. I suppose you could run them higher they're, not really going to be too pushed, i'm not sure they're rated, but i think they're more designed as a visual effect. You'll often find these in the lights spiraled round, with big long gangly filaments and little supports, and quite nice, that they're low voltage, though it opens up possibilities of using them in sort of like costume effects and they're very resilient. I did manage to damage one though i put in a connector and then i really absolutely flailed it off the table to see if i could break it, and what i did manage to do is break one of the solar connections and also fracture the circuit board.

With the flexing where it went onto one of the connectors, so if you reckon there's going to be a lot of movement, put a bit of heat shrink sleeving over the end, just to actually reinforce it. I've actually put heat shrink sleeving, where i've soldered these end. To end, and because i've got four of them, the four times three, it runs at 12 volts but uh. I would go by limiting the current i'd, adjust it to whatever it limits the current to a safe level.

For these, so i shall provide a link to where i got these, but be aware that they are kind of reject factory, rejects they're, just for playing with, and also be aware that sometimes, when i provide links to aliexpress sellers, the price goes through the roof. It sometimes happens. It happened with this. I made a video about this little uh portable soldier yarn, one two, three four, five right: that's it and the seller just hiked the price up, uh more than double so i removed the link and i told them why i'd removed the link um.

They just sent a wee question mark back to me. No, i don't know if they understood what i was saying. I was saying, stop being dicks. However, it's also worth mentioning that there are other tempting things available from this seller, like colorful, solid, led filaments.

These are the higher voltage ones, but these ones arrived intact and these ones all arrive, broken and they're. They were shipped in ten little bags just in amongst other stuff and you're thinking. Oh, maybe they've broken the shipping, but i've had experience with buying the filaments from china. I get the feeling that they quite often just throw the broken ones into the packaging as well, so i'm not sure if they were broken in shipping or if they were broken before shipping.

However, they weren't packaged correctly just be aware of that. If you consider buying the the solid filaments, but that is it so what you see is kind of think of for this. Well, it's just a visually nice thing. You could make yourself a necklace out of it, i suppose, with a little uh battery pack, because it doesn't take much current, even at just 10 milliamps, it glows quite brightly, it's pretty good um, but really it's just whatever you want to do that.

Fundamentally, it produces a nice sharp line of light, but that is it that's how they make it uh the construction inside i'll check back later and see if the stuff that i put in the solvent has dissolved in any way, sometimes the silicons kind of puff up. When you put them in acetone and things like that, but so far no luck, but if that i do have luck i'll, maybe make a note down below in the description or whatever. But anyway, that's it. The gangly very flexible, led filaments.

17 thoughts on “How long led filaments are made”
  1. Avataaar/Circle Created with python_avatars Assassinlexx says:

    What would happen if you raise the voltage on the red.?
    Could you weave the strings to get a new style atomic light 🤔

  2. Avataaar/Circle Created with python_avatars Oscobblepot cobblepot says:

    Less than three minutes in and I’m already bloody lost. Mmm glowy spaghetti

  3. Avataaar/Circle Created with python_avatars Hola! Russ Cole says:

    At what temperature does the solder paste melt at? Asking ad I've never used it before, and looking for an easier way to solder together some very small brass tube as part of a model project

  4. Avataaar/Circle Created with python_avatars STONEDay says:

    High was just thinking about this stuff. Not impressed with the yellow look of the green string. Is it just washed out on camera? Oh..the light is not even either. Boo.

    Nice it's on eBay! (I only use PayPal online). Let me buy it now before the price jumps.

  5. Avataaar/Circle Created with python_avatars Ed Reynolds says:

    The difference in brightness has to do with the color spectrum. Red will always look dimmer then any other color for instance while still having the same voltage or wattage.

  6. Avataaar/Circle Created with python_avatars Rushil Kisoon says:

    I was curious as to why they had such short lengths… then I realised it’s meant for those “filament” type light bulbs.

  7. Avataaar/Circle Created with python_avatars PedroDaGr8 says:

    I just found what project I'm going to use toteach my godson and his sister how to solder. Who knows what we will end up making but these flexible LED strips are what we will use to do so. They both are hardcore about learning how to solder so it should go well. I might propose some ideas but I want them to help design their own creation. The learning how to plan to achieve their goal is the important part. Thank you Clive from the bottom of my heart for posting these.

  8. Avataaar/Circle Created with python_avatars pyromaniac303 says:

    Bought some of these now, great find! I was looking for something like this for a while now for my water fountain illumination project – ruled EL wire out due to the high voltage.

  9. Avataaar/Circle Created with python_avatars sulpheralchemist says:

    I've been playing with these for a while after seeing the tested video too. I've found that a pair of them in series run really well from a usb without need to current limit (as they are under volted). Makes them really easy and good for simple costume work.

  10. Avataaar/Circle Created with python_avatars BRUXXUS says:

    This is what I dreamed EL Wire could be. If they could make these as long and durable as EL Wire while keeping the benefit of LEDs, it'd be amazing!

  11. Avataaar/Circle Created with python_avatars DC Allan says:

    Nice effects tested's neon looks OK. this type of strip could have so many uses I might get a few and play.

  12. Avataaar/Circle Created with python_avatars Moe M. says:

    I think the ends are brighter as you have higher voltage drop there, because all the current is concentrated in one of the two busbars.

  13. Avataaar/Circle Created with python_avatars Gadgetboy says:

    The pick and place machines use tiny little tubes that pull a vacuum and the part sticks to it. Then it goes to a certain X/Y coordinate, pushes it into the paste, then releases the vacuum.

    On occasion, the vacuum might not release fast enough, or the part might stick to the tube, or whatever, and the part won't stick flush. We called it tombstoning when they'd successfully solder flipped up. It was then that I learned that high frequency RF circuits are sensitive to their inductors flipping up – they'll "work" but at a slightly different frequency.

  14. Avataaar/Circle Created with python_avatars Texas1FlyBoy says:

    Thanks! I got my order in for a few to play with. About $9.20 USD (includes shipping and tax) for 5 pieces of 300mm to USA.

  15. Avataaar/Circle Created with python_avatars Brian says:

    That's pretty rad. Mind sharing the video of the model neon you saw Clive?

  16. Avataaar/Circle Created with python_avatars evilution says:

    They call it tombstoning when SMDs flip up when the solder paste is flowed. That's liquid surface tension working against you.

  17. Avataaar/Circle Created with python_avatars Lake Nipissing says:

    Wow!! It looks like colored wires that light up!

    These look like they would be a lot of fun to experiment with!

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