Wondering About LEDs...Answers Not So Clear

[Weaver]

Let me start by saying I am a complete novice as regards electronics in general, let alone saberbuilding. I want to start small, as the tutorials suggest, and the best way I thought to do that was to begin with wiring an LED and power source. The trouble I encounter is that the mishmash of numbers and equations I see is both frustrating and confusing; especially since the only answer I truly want is which BuckPuck or resistor to attach to any given LED.

I knew that beginning with the RGBW that I immediately wanted as soon as I saw it was probably a bad idea, given that it is inherrently more complex than wiring a simple, single-color LED, so I have set that goal aside for later. The initial stages of my trek into the land of lightsaber building must begin with the ins and outs of voltage, current, resistor values, etc. Simply put, I want to know what will and will not fry the diodes I've purchased.

Let us say that I've settled on the LED Engin 10W Green. I read the data sheet and was not totally confused (although close to it) by the jargon it held. What mattered most to me was the "Absolute Maximum Ratings" list near the end. On that list it is hinted that the LED cannot receive more than 1,000mA of current, but it is not directly stated (at least, not in language I'm familiar with). If my estimations and research are correct, selecting a 1,000mA resistor (or BuckPuck) will regulate the output of current to 1,000mA with a minimum input voltage of 5v and a maximum of 32v.

If this is correct, then it stands to reason that I could wire up, say...two lithium ion batteries (7.4v?) to the 1,000mA BuckPuck and power the LED with exactly what it needs without frying it. If this is not correct, I need to start over from the beginning and reread everything I've read in the past two weeks.

Assuming the prior solution is correct, I would like to attempt to convert a storebought flashlight (2D Maglite) into a lithium ion LED Engin 10W White. That is the goal of my first attempt to learn this skill. Everything I've read says it should work, but I'm cautious about taking the plunge.

I know the knee-jerk reaction of veteran electronics geniuses is "Do your research", but I have done. I still have questions and concerns. I don't want to do this incorrectly.

[Skottsaber]

Things to note about reading datasheets, with electronics specifically:

"Absolute maximum ratings" are of the product only. No big copper heatsink like we have in sabers. They are still only recommendations, the company that makes the LED with an x-thousand hour working life guarantee isn't going to tell you to overdrive their product.

Your electronics solution would definitely work, and quite efficiently too. However, if you want to take full advantage of a 10W I would recommend the adjustable LED driver in the store, which can go up to 1500mA for the extra boost, while performance of the LED won't suffer (for a few years' worth of the time it's lit up).

[Weaver]

Skottsaber, thanks for the quick reply. Unfortunately it seems as though both TCSS and Ultrasabers are both wiped out of most of "the good stuff" right now. I blame the holiday.

I suppose I should take this time to review other builds and strategies, just so I know what I'm doing (or so that I think I do). Since we're talking about electrons, am I to understand that the Petit Crouton (snicker) basically functions as a voltage regulator on its own? As I understand it, (just reading from the product description, admittedly) the PC will take up to 9v/2A input without baking. This should mean that the Li-Ion setup I mentioned earlier would in no way endanger the safety of the board.

If I did wire up the board, based on what it says in the manual, I should be able to directly program its output from 0mA-1A+, thus eliminating the need for the main LED resistor. The shimmer is self-explanatory, being able to fluctuate the power from the current maximum output to whichever minimum is selected (must be enough to power the LED, of course), as well as set the duration of each cycle (how quickly the shimmer occurs, etc). The accent LEDs, however, will require resistors. I think this is because they are wired separately from the main LED drive.

Just to put it to rest, once and for all, does Flash on Clash require a totally different LED color, or can I just wire up the second pair of dice to the FoC circuit? It seems to me that the additional influx of light, as well as the different flicker pattern, would show up nicely even as the same color. I wouldn't want to push it by wiring only one of the four diodes as FoC; it might not be bright enough to be seen.

Sound, if I'm reading this right, is drawn directly from the battery and should not need to be calculated into the power requirements for the LED. Will the speaker need current regulation, or do I just pick the right speaker rating and hope for the best? I also see that the Flash on Clash needs to be wired separately from the main LED set (sucks, was hoping for a second "flicker effect", so that I could push all four "dice" for the blade), also configurable through the board setup.

Long story short, from what I see, don't overpower the board and don't set the parameters too high for the LED drive. Is it really that easy?

EDIT: Hrm...I'm also seeing that the Power Extender is needed for FoC. It basically says I'll need a resistor, since the power comes directly from the battery pack. I suppose I can test the voltage with a multimeter, then pick the right resistor.

I want to try adding features over time, such as a recharge port/kill key, a power level indicator, RICE port, etc, etc. I'm sure those can come later, after the main "guts" are assembled. If I don't fry anything, that is.

[Silver Serpent]

To answer a few of your questions:

The PC was designed to run on a pair of Li-Ions. 7.4v is the sweet spot and it'll work perfectly there.

Yes, the PC regulates voltage for the main LED. No resistor is needed for that. Amperage is controlled from a config file.

FoC doesn't require a different color, though you must be running an LED with individually addressable dice. GGGG, RGBA, etc. You can have a GGGG and it'll flash a brighter green.

Speakers aren't too picky. There are now two of them in the store that work perfectly well.

You seem to have a good grasp on most of the information. I'm sure you'll have this wired up in short order.

[Weaver]

You're kind, Silver Serpent. To be honest this looks like a daunting task, and there's quite a bit of money involved. I've never exactly been rich, so waste is not an option. You do it right or you do it twice, and I can't afford the latter. That's why I ask so many questions.

I was thinking about that MagLite conversion for a first project, but now it seems like I should just wait until I can snag all the right parts one at a time. With the holiday rush and all, it seems like what I need/want isn't available right now. When things start restocking I want to start collecting parts for a Luke ROTJ clone. It was easy enough to mimic in the MHS builder and I know exactly what I want it to do.

Thanks again for the information. I just have to screw up the courage to order the parts and begin my experiments.

Just as a side note: I was looking at the really snazzy Li-Ions (Trustfire 18650s). They total 7.4v if I have my math right. Will they work with this setup?

[Merana33]

Electronics can be tricky to understand, especially for the beginner. God only knows how much trouble I had.

Most soundboards (aftermarket ones anyway, I'm not sure about the MR/FX ones) have some sort of voltage regulator built in, and can take a wide(ish) range of input voltage. Typically this is 3-12v, but you'll want to check your boards documentation to be sure. Too low and it wont do anything, too high and you'll let the magic smoke escape. (ie:fry your board)
LED's on the other hand typically have a specific and pretty narrow voltage range that they will work at. Usually this is in the 3-5v range, but I've seen higher. Again, the documentation on your LED will have this information, along with a lot of other highly technical stuff that you will likely never need.

The big things that you want to look for in your LED documentation are the 'forward voltage' (V_f), the 'forward current' (I_f), and the 'peak forward current' (I_fp).
Since I'm also using the LEDengin RGBW for my own saber build, I just happen to have that datasheet handy. You'll find the voltage information on the top of page 5, and the current information on page 6.

One thing to keep in mind with these multi-die LED's is that you're really not dealing with a single LED. You're dealing with a bundle of 4 separate LED's that are all crammed into that single chip. Each LED die may have slightly different characteristics, so you'll want to keep an eye out for that. For example the Red die needs between 2.24-3.2v while the Green die needs 3.68-5.12v. Big difference there!
Now you -can- over-drive an LED but be careful. Pushing past the Max ratings will make it brighter, but push it just a smidge too far and it'll get real bright very briefly before it overheats and burns out (this is why we use those massive heat sinks).

With Batteries this gets slightly more complex because the terminology is similar sounding, but isn't the same. Batteries have a specific output voltage that's pretty much set in stone (when dealing with a single battery or a cohesive battery pack) such as 1.5v, 3.2v, 7.4v, etc. Where things get fiddly is the mAh rating. The 'h' in that abbreviation stands for 'hours'. So a 1000mAh battery can (provided the internal chemical reaction can manage it) output 100mA for 10 hours, or 500mA for 2 hours, or 1000mA for 1 hour, or even 2000mA for 1/2 hour. As you get to the end of that time frame the voltage starts to drop, how fast depends on the chemistry involved. Alkalines tend to fade slower, while rechargeables (especially li-Ions) tend to fade very quickly right at the end. Think of a battery like a car's gas tank and you'll have the right idea.


Having a soundboard in the mix takes a lot of the 'icky math'^tm out of the electronics wiring, but it's good to know how to figure out the resistor you'll need for a setup. You can either do this the old fashioned way and calculate it out using Ohms law, or you can use an online calculator like this one: http://led.linear1.org/led.wiz
Remember that the values you're putting into the calculator are for what you're feeding your LED from your source (either your board or if you aren't using one, your batteries.)

[Weaver]

Ok, now I'm confused. The LED Engin 10W GGGG says maximum forward voltage of 19v @ 700mA, but "binned with all dies in series". Does that really mean 4.75v if each die is separately powered, or 9.5v if linked in pairs? Then we have to address the issue that the LED claims 1,000mA maximum forward current, which is what I wanted to run. If I have my math right, that means the whole LED would need 13.3v @ 1000mA and each die would need 3.325v @ 1000mA

So...if I'm putting 7.4v in, and the LED needs only 3.325v per die, is there a chance I could blow the LED by linking up a single die, even though the board is set within the mA tolerance for the LED as a whole? Or does the board regulate the voltage automatically and the current by whatever parameters are set in the config file? Another member seemed certain that 7.4v in was the "right" power level.

If we assume that the above statment is true, then wiring an LED Engin RGBW with three selector switches (R, G, B) and FoC (W) would basically require that the power source be limited to the lowest maximum voltage of the four dice. Unless, of course, I'm wrong about the board and it does regulate voltage. I wouldn't know, because I'm new.

I'm not even touching a soldering iron until I know exactly what I'm doing. This phase is purely R&D.

[Sunrider]

You need to do more reading. These questions have been answered soooo many times.

[Weaver]

The assumtion made is that I've given no effort to find these answers. I would not ask the question if it were that easy. Still, I will look again.

EDIT: Best answer I can find is that volts disappear from the equation when using the PC-U (http://forums.thecustomsabershop.com...d%29-Read-this), and that only the mA current value is needed. Thus, the board does the work for me and I don't need to worry about the individual voltage requirements of the LED dice (within reason).

It would just be nice to have it confirmed, rather than rolling the dice on more than $150 worth of electronic components.

[Sunrider]

Yes. Like it says in the manual, you set the current (ma) in the config file. All Constant Current or Buck drivers Provide this function and are much more efficient than a resistor.