NB and resistors questions

[Forgetful Jedi Knight]

They don't likely make .3 Ohm .5W resistors, which is why I recommended the .5Ohm, .5W, which I do know is made. You can also use a 1 Ohm, .5W resistor.

[Kagetora]

They don't likely make .3 Ohm .5W resistors, which is why I recommended the .5Ohm, .5W, which I do know is made. You can also use a 1 Ohm, .5W resistor.

Right...I'd have to put resistors in parallel to get to .3 ohms, most likely.

Would running it with the .5 ohm resistor dim it significantly in your experience? My faulty math give me 1A with a .3 ohm resistor (.3/.3), but only 600mA with a .5 ohm resistor (.3/.5).

Also, on a COMPLETELY unrelated note, I was wondering if either of you had a suggestion for which charger to grab from the store for the Li-Ion battery. I was just going to grab the 3.7V Li-Ion Smart Charger with 2.1mm plug for $10, since its going to be dedicated to the saber anyway (didn't figure I needed all the modularity of the other chargers).

[Forgetful Jedi Knight]

Right...I'd have to put resistors in parallel to get to .3 ohms, most likely.

Would running it with the .5 ohm resistor dim it significantly in your experience? My faulty math give me 1A with a .3 ohm resistor (.3/.3), but only 600mA with a .5 ohm resistor (.3/.5).

Also, on a COMPLETELY unrelated note, I was wondering if either of you had a suggestion for which charger to grab from the store for the Li-Ion battery. I was just going to grab the 3.7V Li-Ion Smart Charger with 2.1mm plug for $10, since its going to be dedicated to the saber anyway (didn't figure I needed all the modularity of the other chargers).

No, It won't dim the LED much if at all, and it'll get 1A.

The 3.7V smart charger should be fine for you.

[Kagetora]

Sweet. Thanks again, both of you, for all the help.

[JDuffPhoto]

Can I jump on this discussion? I'm having some trouble figuring out which resistor to go with on my build. I had a PC1.6 in my saber until last night. Didn't like the way it fit into the ribbed section of my hilt, so I am going with the NB board instead. I have a Lux Rebel Amber, drawing 3.2V at 700mA. I'm using a 18500 3.7V power source. Doing the math, the best I can come up with is this

(3.7-3.2) / .7 = 0.714 ohm

Calculating the wattage:
(3.7-3.2) x .7 = .35Watt

I'm looking over the general wiring diagram on the NB manual and it shows a 3-5 Watt resistor in line with the LED. I'm going basic with this build - I'm not even lighting up the LED ring on my switch, so the main LED is it. Can someone look over my math and tell me where I'm going wrong here? Any recommendation on a resistor?

Thanks
Jon

[Forgetful Jedi Knight]

Your math looks pretty fine. You would need a .75 Ohm 1/2W, but since those are hard (but not impossible) to find, I would just go with a 1 Ohm, 1W resistor.

[JDuffPhoto]

Thanks FJK - I found some resistors online and have parts in transit. I'll post an update on my other thread when I have some more pictures and this time I'll include the chassis and wiring.