Direct Driving LED's

[JediKnightBJ]

What configuration can I direct drive the following LED's?

Red Luxeon 1-
Green Luxeon 1-
Blue Luxeon 1-
Cyan Luxeon 1-
White Luxeon 1-

I have searched, but I can't find any posts about the Luxeon 1's.

Sorry if this is already out there, I can't find it.

[Lord Maul]

I'm driving a starO with 2AAAs and no resistor. Technically that is overdriving it a bit, but it's a small amount.

Any 3V battery will drive it fine, or you can wire to 1.5V batteries in series (what I have)

[JediKnightBJ]

Thank you Lord Maul. How would direct driving it compare to using a micropuck to regulate current?

[Novastar]

To "direct drive" an LED (and let's consider if you did it WITHOUT a resistor... which btw is dangerous if you don't know what you're doing):

1. Identify the LED's "forward voltage" (using the manufacturer's specs is good for this).

2. Put together a battery solution that is IDENTICAL or just below the LED's fwd voltage.

3. Make certain your cells don't have some insane amp draw allowed out of them... or better yet, they are AA Alkaline, AAA Alkaline... or Li-Ion with a PCB (which will limit current draw, among other protective things).

An example:

Luxeon III Red-Orange (2.95 fwd v)
Alkaline AA wired for the voltage (1.5 x 2 = 3.0v)

Luxeon III Green (3.85 or 3.9 fwd v)
Li-Ion 18650 (as example) 3.6v cell

In the latter case, even though the Li-Ion cell's rated voltage is somewhat below the Luxeon's suggested fwd v, it should still light up nicely and do just fine.

As to your question about pucks/bucks (so, DRIVERS) vs. *ANY* kind of direct drive solution... they are 99.8% of the time better in several ways:

* CONTROLS the current intelligently
* Saves/extends battery life
* Reduces chances for "killing" your LED
* Usually going to producing less heat (if the current is being pulsed or "flickered")

That's about all I can say, although sure there are more details that someone with a THRONG more experience could tell you.

[JediKnightBJ]

Let me see if I understand this by giving an example. I am looking at Lux 1's. Most of the forward voltages are 3.42v. I could viable run them, however a bit dimmer, at 3.0v direct driven with 2xAA batteries.

Ok, on the driver end of it. I'm using a micropuck to drive my royal blue Lux Star 1W. The forward voltage is 3.42v and I'm running it with 4xAAA batteries. When I test the voltage after going through the LED its comes out at 6.0v-varies a bit,but average of 6.0v. Is the micropuck protecting the LED from the voltage?

Sorry, i'm just trying to make sure I understand this.

[Lord Maul]

The micropuck will protect your LED, no worries.

[JediKnightBJ]

Last question I promise, no i don't promise.

If I use NiMH cells. 1.2v each. If i use three, that would produce 3.6v. The max forward voltage on most of the Lux 1's I use is 3.99. Would that be safe enough to direct drive those?

I am direct driving a Lux 1 red in my curved PVC hilt, and its beautiful. Its my first red saber.

[Eandori]

Honestly, if you don't have a solid understanding of electronics basics, the non-linear V/I curve of a diode, and the finer points of batteries under-a-load I would reccomend NOT direct driving your setup.

Chances are that you will either under-drive your LED's (dim saber), over-drive your LED's (dead saber), and probably end up buying LOTS of replacement luxeons because you'll fry a lot of them while experimenting and setting things up.

To the experienced Saber Smiths out there...
Seriously guys, we should reccomend AGAINST newbies doing this. If they don't know enough and needed to ask the question, then they most likely have many gaps in understanding and will end up frustrated and waiting for new Luxeons to arrive in the mail.

You can't half-ass something like this. If you are going to tell people how to direct drive, you REALLY SHOULD explain the whole thing or you are leading people off the end of a short peir.

[Jay-gon Jinn]

If you have a micropuck, use it. It will drive the led better than a resistor, and also better than direct drive, as it is a boost puck, which will allow you to run an led at less than the forward voltage....i.e. your green Lux I requires 3.42 vf, but the micropuck will allow you to run the led with just 3v. It will also maintain the led's brightness until the batteries get really low. You can read more about them here:
http://www.leddynamics.com/LuxDrive/datasheets/2009A-MicroPuck.pdf

[Eandori]

I totally agree with JaygonJinn. Micropucks do voltage up-conversion (for small voltage ranges at least) so it would work for you. In general, a current driver board or circuit will be FAR better then direct drive or a resistor.

This has been covered in other threads in detail why it's better. Don't do direct drive.

[Novastar]

I just wired up a Lux V with 7.2v Li-Ion, and a resistor setup that is 0.75 ohm, 7.5 watt capable.

After FINALLY learning how to meter the current last night (with a little extra help from Do-Clo, thanks!), I can see that on this setup, the circuit is running around 1260ma at full charge.

As the minutes go by, somewhere around 10 minutes in, we're closer to 1000ma. Much later, I see 900ma, and finally (probably somewhere near a "middle" charge) around 750ma. I haven't tested it further after that--I don't care... it works GREAT! :)

In my opinion, this particular and very specific setup worked VERY well for me. Granted, for however anyone wants to label "direct drive", whether using a resistor or not... you will have to come to your own conclusions.

I might even try wiring a simple spring/vibration sensor (N/O) that BYPASSES the resistor when the spring is triggered (now closed). At this point, the current would briefly be over-driven, and we'd get a little flicker. Sounds good to me!

Regarding safety, with my battery setup and the PCB, everything is pretty safe thus far. In the 2+ years I've used Li-Ions--and I've now wired up about 20+ sabers of differing kinds, mostly powered by Li-Ion... I never once had a disaster with these 18650 cells--with the exception of that bizarre 11.1v pack (which were not 18650s anyhow) that was originally in the green H-blade (which one day set itself ablaze). It wasn't my pack to begin with, and I have no idea how it was wired up. It certainly got hot in the H-blade though... bloody hot!

I can understand people recommending drivers, but... I honestly don't see the point if the saber doesn't have sound, or... the driver doesn't really offer anything of import that makes it cost-effective to use over the "el-cheapo" resistor way.

Finally, I have found that direct-driving Luxeon LEDs with both Li-Ion cells and even Alkalines to be "safe", but only if you know what you're doing, and WHY. In general, "direct driving" with no resistor will reduce the already ridiculously long life of your high-powered LED, make it brighter initially... but also generate a lot of heat. I would never recommend this with Ni-Mh cells, as they have an INSANE ability to draw amps (as I learned from Eandori's experience)... and I personally think they are not the safest solution for sabers if some disastrous short circuit occurs, or they are allowed to deliver amps with no "control" over them!

NEVER direct drive an LED if you know that the amp draw of your battery setup is just ridiculous, and NEVER try sending (for example) 7.2v into an LED which has a forward voltage of 3 or 4 volts.

Maybe I've just been "lucky". Or maybe I've just chosen the right cells for the sabers I have... I'm not 100% sure... but pretty darn sure! :)

[Eandori]

I can understand people recommending drivers, but... I honestly don't see the point if the saber doesn't have sound, or... the driver doesn't really offer anything of import that makes it cost-effective to use over the "el-cheapo" resistor way.

1. A current driver will not fry your LED if you use the wrong battery.
2. A current driver will keep your LED at MAX brightness for nearly the entire runtime. Not overdriven (10 min), properly driven (10 min), then underdriven worse and worse for 110min.
3. A resistor is not a current driver. A resistor is a passive device, a current driver is an active device.

Although (just like you said) your 7.2v Lithium Ion setup worked with direct drive, if you had a charger hooked up and for some reason your (disconnection) circuit failed and you turned on the saber while charging you might fry your LED. Because you could get current from the LED, plus current from the charger and that might pop the LED.

NiMH can output more current then Lithium Ion so they are more dangerous with a short in that way. But NiMH does not explode when cells are shorted. Lithium Ion and Lithium Polymer do. THAT IS WHY THERE IS A CURRENT LIMITING CIRCUIT ON THEM.

If a saber maker is knowledgable enough with this stuff, they don't need our advice on how to set up their sabers. If they didn't know this stuff coming in here, I would rather not be the guy telling people to direct drive when I don't know what their understanding is.