Direct Driving LED's

[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.