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Thread: Series Vs Parallel? Brightness/functionality? Oh and batteries.

  1. #1
    Youngling Zahc Zi Phan's Avatar
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    Default Series Vs Parallel? Brightness/functionality? Oh and batteries.

    Hey all. Sorry if I dig up old posts, I've been digging on here for a few hours now and I am not really finding what I am looking for...

    I am curious about wiring LED's series and parallel. I am not sure exactly what this means. The last time I built a saber, single die rebels were the big thing. So yeah. A bit inexperienced. Not asking to be spoon fed, but I would love some insight.

    I plan to build a pretty nice saber using TRI-CREE XP-E2, CF 7.5 or PC 3.5, with crystal chamber, and Cex or Pex depending on what I decide. I am pretty mechanically inclined so not worried about the fine details. What I am curious about is the differences in wiring and the level of brightness the blade will have. I would like this thing to really pump out the lumens. I initially wanted to use a Cex and mix, but I heard somewhere simply running two dice of one color makes for a way brighter experience.

    I have a few questions.

    1. My understanding is that parallel means two dice are wired together and therefore acting as one. I also understand when using GGW or BBW, wiring two of the same color together and using white for FOC makes for a very bright saber, with no color mixing. Correct? So am I to understand that if my board drives a main LED up to 2A, when wired parallel and driven at 2A, each die will get 1A and be safe (not in danger of frying)? Resistors required?

    2. My understanding of series is that each die is wired and controlled separately, allowing for more finely tuned operation and drive current to each dice, such as for color mixing. Correct? Thats where my understanding fades. I'm not sure how or why I would wire these in series other than to mix colors?

    3. Scenario. I have a color mixing saber and currently have die X and die Y going strong to make Z color. Is there a significant difference in brightness between a color mixing saber and a dedicated color saber using TRI-cree? I know to achieve certain colors, only one die will be running at a time, I am just curious what the difference would be. The only thing I have to gauge brightness against is my saber with single die red rebel running @ 700ma. It's kinda bright... Ish.

    4. looking for a battery solution. I plan on using a 7.4v PCB protected pack. The largest one in the shop is 2600mah (2x18650). I know that means that it can run 2.6A for one hour. I've been looking around for larger capacity packs, but they're all huge. Even the 2600mah would be pushing it for size in my hilt with everything I want to cram in, but if it had a significantly larger capacity, I think I could justify it. My question is about building packs since I know you can't link to elsewhere where you could find a larger pack. If I take two 3.4v 3400mah cells and make a PCB protected pack, would it therefore be 6800mah or still 3400mah? Is it a pretty dangerous ordeal to make a pack? I know a fraction of an amp can kill, so I am just curious.

    5. For poos and giggles, how would a tri-cree compare to a single rebel in terms of brightness? Pretty substantial?


    Thanks in advance for any answers/insight. I'm trying to get back into this so bear with me. Wont be a Padawan for long. I learn quick thankfully.

  2. #2

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    You have the definitions for in parallel and in series a little mixed up.
    1. A parallel circuit will halve the amperage but stay at the same voltage, 7.4V in your case, acting as two separate, parallel circuits.
    2. A circuit in series will halve the voltage but run at the same current, operating as a single circuit.
    In order to mix and control the individual dice, you would need to wire in parallel. For a PEX flash on clash, you wire the two colour dice in series and the flash in parallel.
    3. With the drivers you listed, there would be little difference between a mixed colour and a dedicated colour since they can easily drive both dice near their maximum.
    4. As for making battery packs, you can make a 6800mA pack at 3.7V with the cells wired in parallel or a 3400mA pack at 7.4V with the cells wired in series.
    5. When comparing a tri-cree to a single rebel, the difference will be pretty substantial.

    I think this is right but I'd let some of the more experienced builders give their input first.

  3. #3

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    1. You're about half right on the series/parallel setup. In parallel, the two dice are wired separately. You can resistor each die individually. Current is split evenly among the dice, but voltage remains the same. So a GG wired parallel would only need the voltage of a single G, and giving them 2A would yield 1A to each die. Parallel wiring is used for color mixing.

    2. In series, you wire the dice together, positive to negative, effectively making a single LED (electrically speaking). You will add the voltages together, but the current requirements are equal to that of a single LED. For the GG example above, you'd need double the voltage, but only 1A of current. Series wiring gives a longer runtime, but you lose the ability to get specific color shades.

    3. The Cree LEDs are pretty much superior for every single color. There might be a few exceptions, I'm not sure. If you're comparing a single die Cree to a single die Rebel, the Cree nearly always wins. If you're comparing two dice (Cree or Rebel) to a single die, the double always wins, in terms of brightness.

    4. Yes, you can build your own packs. There is a pretty good tutorial here on the forums for just that. If you use two 3.7v 3400mAh cells in series, you'll end up with a 7.4v 3400mAh pack. If you use them in parallel, you'll have a 3.7v 6800mAh pack.

    5. Very substantial.
    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!

  4. #4
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    Beaten to a degree but I'm typing slow...

    You're understanding is incorrect... it's actually almost reversed.

    In parallel you need double the amperage, but the same voltage. In series you need double the voltage, but the same amperage. If for example you're running a BBW LED... you can theoretically run the blues either way and see no difference! It's up to other factors such as your batteries. If you have a 7.4V li-ion battery pack you're not at an ideal voltage for a series setup.(1V above the LEDs for blues, Reds it would be more dandy sometimes). The downside of parallel is the large power drain. If you're a heavy user it'll be like your cell phone battery eventually it won't work nearly as long. You might even trigger the protection PCB with a high draw (3A if you have 2 LEDs at 1A and then the clash at 1A).

    I personally am of the opinion that for two die and clash setups like BBW you should always run in series. My reason is this: I'm working on a BBW saber right now. The forward voltage of one Blue is 3.1V and the other 3.6V... these are Rebels I got off the same reel when I put them on a star PCB! If I run them in parallel the lower voltage LED is going to get run HARD and the higher one less so. There's a diminishing return for brightness and the amperage you're running through it so that one LED running hard isn't going to make up for the lesser LED. Series is the better bet for a consistent brightness.

    Color mixing is different. You NEED to be in parallel to do it. Each LED is addressed seperately which is the definition of parallel. Series is "daisy chaining". To use a metaphor: parallel is two hoses from the same spigot. You need to have more water running through (amperage) at the spigot but one hose might flow better. In series it's one spigot still but two hoses end to end.

    #3 depends highly. If it's a natural LED color you'd otherwise get with a single LED I think you'd be getting too complicated. If you want the ability to change you go RGB and mix. If you simply want the brightest you should go with the multiples.

    #4 Depends on how you wire them. Again it's series vs. parallel. If you have two 3.7V cells that are 3400mAh you can either make a 3.7V 6800mAh pak or a 7.4V 3400mAh pack. I don't think it's hard to make your own pack if you have a good soldering iron.
    RED LEADER Standing by!

  5. #5

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    It is very apparent that we were all writing our replies at the same time. Fortunately, we all said the same thing so you can be sure about the information.

  6. #6
    Youngling Zahc Zi Phan's Avatar
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    You guys are really awesome. I appreciate the help and that makes much more sense now. Thats why I love this forum, such kind individuals willing to give their two cents and help out a fellow enthusiast. It means a lot to have my questions answered and not be chewed out.

    So the consensus is, after watching a video by Erv himself, I'm going crystal focus and getting a tri-cree RGB. I can't justify not going for color mixing, especially when I can't make up my mind and decide what color I want. Might as well do the logical thing and have them all. It will also be simpler for me, because the CF 7.5 has very detailed instructions about how to wire up the star and crystal chamber, so I don't have to decide which way I am going to wire everything up. Winning.

    Man tonight has been great, I just got news from Cakira earlier that my switch setup idea is going to work great (MHS claw mount drilled and tapped to hold 2x 12mm vandals). Then this. It's all coming together and it's all because everyone here is so very helpful.

    Thanks again guys.

  7. #7

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    Parallel is the only way to go for color mixing. It will shorten battery run-time, but 2600MaH is fine. If you ever do a single color blade, ex. Blue-Blue-White(for FoC), and your battery has more voltage than the sum of the two blue dies, run the blues in serial.

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