Please help! Quick question about my wiring/resistor set up with Tri cree BBW

[zannahishott]

I am in the process of wiring up my LED to achieve a light blue color. I am having great difficulty getting this right. I have read a dozen threads and watched/read almost every tutorial I can find on LED wiring and resistors. I have even sat down with pen and paper and done the math. I am really trying to express how not lazy I have been right now.

Main issues:

- Blade color needs a little more blue
- can't figure out right resistor placement to make that happen.

I am using a tri cree BBW, two 3.7V 2000mAh AA batteries, no soundboard, momentary switch. At my disposal I have a .47 ohm 5 watt resistor, two 1 ohm 10 watt resistors, and 2 dyna ohm resistors.

From my research, I am thinking that I need a resistor going to each separate LED, but without a board how do I wire that? Do I split the positive wire up? Should they be in parallel or in series?

Do I go power supply, switch, dyna ohm, blue LED, dyna ohm, white LED, back to negative?

I would really appreciate all the help I can get.

[Zahc Zi Phan]

I'm not a master with multi die LEDs yet, nor do I have experience building static sabers (everything I have has a soundboard) but I can tell you if you are using the 20ma Dynaohm resistor from the store, that is designed for an LED that has FIFTY TIMES less current than your LED star brother. The star should run at 1000ma, 20ma is for small LEDs like the ones in the AV switches.

[Thalan the Exiled]

If you want a light blue you probably want to run the blues at full and play with the resistor value on the white tto get the color you want. The white being the brightest of the three will probably over power the blue if you ran it full. Noa for the blues yoy could run them either with a resistor on each or parallel/series. Use http://ledcalc.com/#calc to figure out the resistor value for which ever way you decide. I personally put a resistor on each. I split the positive wire into 3 and resistored each diode and ran a single negitive, bridging between the pada for each diode. This will allow you to adjust the resistor value on each till you get what you arw looking for. Hope this helped.

[zannahishott]

Thank you both for the responses!

So Thalan, what you are saying is that is completely okay to split the positive into three, put a resistor on each to get the color I want, then run negatives to each negative pad on the diode and then have one negative come down from the LED? That sounds like it would work!

[Grimlock84]

Remember running LEDs in parallel splits amperage but keeps voltage the same and running them in series splits voltage but keeps amperage the same. If you run them in parallel 2 blue LEDs will draw 2000 mA. If you run them in series and have your batteries set up to run at 7.4v then run them in series you'll get a longer runtime since 2 blue LEDs will draw 1000mA.

[zannahishott]

Thank you Grimlock84.

So if I run the blue in series, ignore the white, I can put a 1 ohm 10 watt resistor on the positive before the LED and then everything will be good as far as V and mA are concerned. I like your idea because I may add a soundcard later and use the white as FOC. But you think that set up will work?

[Grimlock84]

You should be able to run the .47 ohm 5 watt resistor if you run the 2 blue LEDs in series and provide them with 7.4v . The 1 ohm 10 watt will work but your over resisting the circuit and your LEDs won't be as bright.

I would use FJK down and dirty ohms law guide and calculate the correct value and then just get the proper resistor.

The link:
http://forums.thecustomsabershop.com/showthread.php?17109-Tutorial-FJK-s-quot-Down-and-Dirty-quot-guide-to-Ohm-s-Law