Wattage on resistors

[Cjhpkns]

So I recently finished wiring up a RGrB Tri-Cree up to my US Apprentice LE v4, and while I was, I had to, of course, hook up resistors to the Red and Royal Blue to make purple. My dad helped me make it, and with his extensive knowledge of electronics and related material, he told me to not use a .47ohm 1/2 watt resistor on my blue LED. He said that the wattage was too low, and told me to get a .47ohm 5 watt resistor. Herein lies my question: could I have used the 1/2 watt resistor? I was using a 4 AAA battery pack (rechargeable, so a bit less than 6 volts). I like my current setup, with the 5 watt resistor, so I'm just asking out of curiosity.

[darth_chasm]

What you're saying doesn't make sense unless I'm reading wrong. Your father said a 1/2 watt resistor was too low then suggested an even lower wattage? 0.5 > 0.47... Then you say you have a 5 watt resistor...

For a 6 volt set up you need at least a 2.7 ohm 3+ watt resistor for the blue. 0.47 wont cut it. And 3.9 ohm 5+ watt resistor for red.

[Cjhpkns]

You're right. I meant 5 watt. It was a .47 ohm resistor. Sorry about that. So I used a .47ohm, 5 watt resistor on the blue, then a 4.7ohm 5 watt resistor on the red, and I got the purple I wanted.

Define "won't cut it"; what do you mean?

[jbkuma]

Rapid unplanned disassembly.

[Cjhpkns]

Rapid unplanned disassembly.

What?

[darth_chasm]

You're right. I meant 5 watt. It was a .47 ohm resistor. Sorry about that. So I used a .47ohm, 5 watt resistor on the blue, then a 4.7ohm 5 watt resistor on the red, and I got the purple I wanted.

Define "won't cut it"; what do you mean?

You need a minimum resistance that will protect your led from receiving too much current and burning out. For an led that is 3.4 Vf @ 1000mA with a 6 volt supply you need at least 2.6 ohms of resistance. 2.7 is the closest most common resistor when rounding up.

Study this http://forums.thecustomsabershop.com...e-to-Ohm-s-Law

Rapid unplanned disassembly.

He's saying you need to fix the issue before you are a very unhappy camper with a burnt out led.

[Tom Tilmon]

Rapid unplanned disassembly.

that sounds like a disaster in outer space, like Apollo 13 or something. Got my laugh for the night at that one. Hey, ever had a "rapid unplanned disassembly?" Yep, this one time..........

Tom

[Cjhpkns]

Is putting a 4.7ohm 5 watt resistor on the battery assembly a viable solution? I'm trying to not mess up the color mix I have made, but I also do not want for my LED to burn out.

Also, if the LED was going to burn out, how long would it take before it would? I've been using this current setup (with the .47ohm resistor on the blue) since this past Thursday.