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Thread: LED filament blade?

  1. #1

    Default LED filament blade?

    Ebay is full of LED filaments nowadays.
    Has anybody tried building a blade out of them? It should be possible to get about 25 of those in a blade, which means about 3000 lumens.
    Unfortunately they require 50-60 volts, so it will definitely need some boost converters, and could possibly get a bit hot since the battery and voltage booster will have to put out 25 watts of power. Still, a good booster can be ~90 efficient, so we'd only put out 2.5W of heat in the booster.

    I was thinking of designing a 12" by ~1/2" circuit board for holding the led filaments, then put as many as those as I need together. The power draw on the 60 volt side is only 0.35A, so it doesn't need any bulky cables. (Power draw on the battery would be around 5A though, assuming a 7.3-volt battery pack.)

    I've ordered some LED filaments, and I found a boost converter that might be powerful enough (if it doesn't overheat) I'll post pictures and stuff here as I go.
    If anybody has recommendations efficient boster ICs/circuit designs, that would be cool. I can build my own circuit boards, but I'm not terribly experienced at it.

    In the meantime I'll be reading up on how to construct the rest of the blade and diffuser.

    /Profezzorn (1st post)

  2. #2

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    Sounds like you'll have an interesting time powering those filaments. It's definitely not going to be compatible with the regular lightsaber tech.

    Good luck, and keep us informed of your results, good or bad.
    We all have to start somewhere. The journey is all the more impressive by our humble beginnings.

    http://led.linear1.org/1led.wiz for the lazy man's resistor calculator!
    http://forums.thecustomsabershop.com...e-to-Ohm-s-Law for getting resistor values the right way!

  3. #3

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    I think I just figured out the easiest way to get the required power: A stack of 20 CR2032 coin cells. With a power draw of ~0.35A, the coin cells won't last that long, perhaps half an hour or so, but apparently you can buy these in packs of a hundred for $30 bucks.

    If there is enough space, I could double the stack of batteries, double the voltage to 120 and connect two filaments in serial. This would reduce power losses and double the battery life. The stack of batteries would be 128mm tall, and I don't have my hilt yet, so I'm not sure how much space I'm going to have.

    The coin cells probably drop some voltage under load, so it's possible that I'll need more than 20/40, . I'll have to experiment and see.

  4. #4

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    LED Filaments are essentially a series of smd type LEDs on a flexible circuit board with a translucent elastomeric. OK so technically they are a series of blue with a few red SMD LEDs and the elatomeric is coated with Phosphor coating. Though some china companies are simply using white leds and translucent yellow plastic dip type material, you can usually see ech individual dot of lite on this type. With some patients and experimentation you could fabricate a string blade using current string blade wiring methods. Just build each of the series wired segments for approximately 7.4v. That way you can use a readily available power supply. You could make your own board using copper clad and etching, or simply have one printed by any of several places offering custom boards. Then wire each of the segments in parallel, heat shrink the whole assembly and now diffuse and insert it into a blade like a standard string blade.

    Either way keep in mind heat is the enemy of any LED, and all high intensity LEDs need to have some way to dissipate the heat. I know there is a white paper on the construction and evolution of the filaments I'll dig it up for you. It might be an opportunity for some of the new thermally conductive polymers that are on the market...I bet there is someone working on that as we speak

    Edit: here is the link http://www.ledinside.com/knowledge/2...filament_bulbs
    Last edited by FenixFire; 04-19-2016 at 12:24 PM. Reason: Added link to White Paper

  5. #5

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    If you are looking at the extremely cheep, low end $.90 ones on eBay the flexible board is simple the thin metal strips you see exposed on the ends.

    Here is the link to the actual manufactures spec sheet. http://www.runlite.cn/userfiles/5cje...1413258994.pdf Also, keep in mind that filaments like these are designed to be installed in pressurized bulbs filled with a cooling gas. The opposite of the traditional incandescent that are in vacuum bulbs. I cant remember it is is this or one of the Philips products that list the recommended gas and pressure composition.
    Last edited by FenixFire; 04-19-2016 at 12:09 PM.

  6. #6

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    I'm not sure how you would wire things up to run at 7.4 volts without getting custom LED filaments where some of the LEDs are wired in parallel. If such a thing exists, I have not yet found it. However, I don't see a problem with either using a boost converter or a stack of coin cells and then controlling the high-voltage circuit with a FET. The FET can be wired directly to the sound board (with an appropriate resistor) to let the sound board control sparks and on/off. If I go with a boost converter, they usually have an "enable" pin, which would eliminate the need for a FET. I found a tool called wbench which can automate the boost converter design, but it is currently giving me designs that include non-existing inductors.

    I've already ordered some led filaments to start testing with, I'll be interested to see how hot they get. If they get too hot I'll have to put a fan in the hilt and create an air hole in the tip of the blade.
    Another option would be to replace the traditional foam diffuser with some sort of epoxy or silicone, which could carry the heat away better. That would make the blade pretty heavy though.

  7. #7

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    You would be creating your own pseudo filament, essentially using smd LEDs instead of standard dome or top hat LEDs.

    The problem you will run into with using the OEM filaments you mention is heat. High intensity LEDs are not like the normal 20mA kind. They all require some form of heatsink either copper, aluminum, THERMA-TECH™ polymer, or various coolant gasses. In the case of the Filaments they were developed as a way to aesthetically replicate the classic Edison bulbs, thus utilizing the principles of the inverse of the vacuum they use a pressurized cooling gas within the glass or acrylic bulbs they are installed into. You can run them for a short period out of the cooling chamber as shown in various youtube videos, though they will not last if exposed to long run times.

    Though I have not seen or tested how long they would last outside of the chamber. After all the rebels and crees are being pushed beyond what they were designed per one of the Cree engineers I know, though he credits it to the fact that the heatsink and LED holder are effectively transferring heat to the entire hilt. Since the filaments will be in the PolyCarb blade assembly and any direct metal contact would short it out, this is not possible with the filaments.

    As for the Fan solution:
    High-intensity LEDs heat up instantly and do not allow time for a fan to cool them before the magic smoke is released. Fans can assist in cooling the heatsinks, but the LEDs have to be cooled through contact. Ideally with either a copper, Aluminum, or THERMA-TECH™. Look at the heatsinks used on the single CREE LEDs in the shop. The filaments are basically 10 of those leds at a 1608 smd size, with no heatsink attached.

    BTW:
    Silicone and Epoxy(clear 2 part not JB Weld) are thermal insulators not thermal conductors. They would actually hold the heat to the LEDs not dissipate it. Thats why they make silicone oven mitts.
    Last edited by FenixFire; 04-19-2016 at 03:18 PM.

  8. #8

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    > High-intensity LEDs heat up instantly and do not allow time for a fan to cool them before the magic smoke is released. Fans can assist in cooling the heatsinks, but the LEDs have to be cooled through contact. Ideally with either a copper, Aluminum, or THERMA-TECH™ heatsink.

    All true, but as you say, the filament don't immediately die when you run them in air. However, in an enclosed space, the air heats up and will eventually kill the LEDs (or melt the surrounding plastic). Even a fairly modest flow of air can prevent this from happening.

    Also, I just realized I have some 4- and 7-watt led filament bulbs at home, I should check out how hot they get.

  9. #9

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    An led will never get hot enough to melt the plastic around it, before it pops.

  10. #10

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    Good luck with your trials, here is a link to an article that will help explain some of the heat issues. http://www.electronics-cooling.com/2...n-led-cooling/ It's not the one I was looking for but it should help out. Even Crees and rebels will work for a few minutes without a heatsink...but then it's too late.

    For the bulbs you mention ther is the thermal conductive gas and the internal assembly transf0er the heat to the therma-thech plastic. You'll need to calculate the surface area and the surface temperature above ambient to calculate the required thermal loading.
    Last edited by FenixFire; 04-19-2016 at 03:55 PM.

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