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Phantom465
06-29-2007, 04:08 PM
This is my first time building a LED saber, so please forgive the n00b questions :oops:

I just assembled a green lux V (http://www.thecustomsabershop.com/pc-778-23-luxeon-v-star-green.aspx) with a 9v battery and 3.3 ohm 5w resistor (http://www.thecustomsabershop.com/pc-821-36-33ohm-5w-resistor.aspx) as called for in this chart (http://www.thecustomsabershop.com/t-resistors.aspx). I put the blade into the blade holder and turned it on to see how it looked. I did not have the hilt put back together yet, so all of the wiring was exposed. I only had it on for 30 seconds, but I noticed the resistor was very warm. Not hot enough to actually burn me, but hot enough to make me wonder.
I checked my wiring for shorts or mistakes, but I don't see any problems. But this raised a few questions for me:

Is it normal for the resistor to get this hot in a short period of time?
Should I worry about having it turned on for an extended period of time?


(yes, I have heard that a 9v won't last as long as 6AA batteries, but this takes up less room in the hilt)

thank you!

LAN-ED-TUL
06-30-2007, 07:06 PM
as said before in another thread, yes it will be warm.

reason is its taking the excess voltage and cutting down the amount goig to the led. so what does the resistor do? as it cuts the voltage down, it will generate heat. heat is normal for a resistor.

depending on your leds forward voltage, and if used a soundboards volatge, and lets assume the board uses a higher amount of voltage, lets say, just for arguements sake, the 9 volts. the led wont take that high a volts. so resistoring it down to its forward voltage, will generate quite a bit of heat for taking the voltage from 9 volts down to lets say, 3 volts. thats 6 volts its taking off before the led.

the other lead runs to board, and as assuming, or hypothesizing above, a 9volt board.

im not the expert, like others here, but you might want to rethink your batt source. like maybe li-ions or something that will get the same amount but be smaller sized.

after glancing at the chart, i see the led is just above 6.5 volts forward voltage. so that resistor is tryin to cut a lil more than 2 volts off the 9 volt, so yeah, its gonna be warm dude.

Novastar
07-01-2007, 10:14 AM
A luxeon V takes about 6.85 fwd v. Powering it with a 7.2 Li-Ion setup is ideal (when using a resistor-only setup).

As Lan said, the 9v need to be "shunted" into about 7ish. The resistor is "wasting" about 2v into heat. As I mentioned on a thread regarding Lux III, V, K2, etc. -- you want to choose a battery setup that is VERY close to the fwd v of your LED... when using a resistor-only setup.

If you use almost any kind of driver board (Corbin's, Ultra's, Erv's, a puck thing, etc.) it won't really become an issue unless it's exorbitant.

Lord Maul
07-03-2007, 09:27 PM
just a FYI on using a 9-Volt battery with a 5 watter: the led will start to dim after probably under 1/2 an hour :wink:

Hasid Lafre
07-03-2007, 09:32 PM
(yes, I have heard that a 9v won't last as long as 6AA batteries, but this takes up less room in the hilt) :roll: