new build question

[amoroso]

Hi all - my first build, so apologies for the noob questions...

I'm starting off simple, a saber for my 12yo daughter. She's asked for a red LED, so here's what I have purchased from Tim so far:

1 4AAA Battery Holder with JST connector
1 Luxeon Rebel Star (Red)
1 Star thermal tape pad
1 Collimator Lens 5 deg viewing angle
1 Cree/Rebel Lens Holder

The hilt will be PVC (1" ID furniture PVC).

I'm trying to stay as cheap as possible for this first build, so I am planning on using a copper pipe end cap for heat sink, and a standard resistor instead of a driver.

From what I have learned, if I power with (3) AAA batteries, for the Rebel Star Red (2.4v, 700mA), I would need a resistor rated for 3.0 Ohm and 1.5 W.
If I power with (2) AAA batteries, that looks to change the resistor to 1.0 Ohm, .5W.

Does all that sound right? Any concerns?

Thanks!!
Tom

[Silver Serpent]

Your numbers are fine. I would personally try to bump your batteries up to AA sized if possible. The AAA batteries don't last long at all.

Rechargeable options are better, but more expensive in the beginning (though they pay for themselves after a handful of charges).

[NanoRex]

If you're going to stick with AA or AAA batteries, it would be best to use two, as the extra 1.5V from the third is just going to end up being dissipated if you're using an LED with a Vf of 2.4V.

[amoroso]

Thanks guys - appreciate the feedback!!