Help: How much resistance? SYOL, 2 CR123, 800 mA

Orion

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I was wanting to know if someone could give me a general answer as to how much resistance may be good for this setup:

SYOLW Luxeon
Two CR123 cells
800 mA

Thanks! /ubbthreads/images/graemlins/smile.gif
 

kj

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Re: Help: How much resistance? SYOL, 2 CR123, 800

I believe that Vf of Luxeon III is measured at 700mA. So, the Vf at 800mA could be slightly higher. Also, because the battery voltage sags at 800mA load, the required resistance should be lower than 2.7 ohm. I actually estimate 1.5~2.0 ohm depending on battery brand and LED variance.

I suggest trying various resistors between 1.5~2.7 ohm and measure the actual current. You will need 2 watts resistors.
 

Orion

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Re: Help: How much resistance? SYOL, 2 CR123, 800

What would happen if I used a 1 watt resistor, or even a 5 watt resistor?
 

IsaacHayes

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Re: Help: How much resistance? SYOL, 2 CR123, 800

With the 1watt you could release harmfull amounts of raydon gas which could get you reported to the athorities. With the 5w you risk the chance of an implosion.

Or the 1W resistor will get hot and possibly burn up and not conduct at all. The 5W would be fine.
 

kj

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Re: Help: How much resistance? SYOL, 2 CR123, 800

/ubbthreads/images/graemlins/grin.gif

1W may be okay, but I would suggest using 2W~ for safe.
 

Orion

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Re: Help: How much resistance? SYOL, 2 CR123, 800

Raydon gas!!! /ubbthreads/images/graemlins/eek.gif I'd better not use a 1 watt resistor then. /ubbthreads/images/graemlins/smile.gif

Any idea as to where I could get a 2 ohm, 2 watt resistor and how much it would cost?
 

IsaacHayes

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Re: Help: How much resistance? SYOL, 2 CR123, 800

if you can fit a 5w resistor in there then just go with that. Or you could get 2 of the 1W resistors at a 4 ohm value, and wire them in parallel. that way you get 2ohms with double the power ratting, which would then be 2watts.

1W and 5W resistors are commonly avalible at radio shack. the 1W are just bigger ones, and the 5W are of the wire wound variety.
 

Orion

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Re: Help: How much resistance? SYOL, 2 CR123, 800

Hmmmmmmm, two 1 watt resistors in parallel. I guess that might be what I do. Seems it should work. I have 1 and 5 watt resistors, so I may be well set up. IsaacHayes, thanks for the suggestion!! /ubbthreads/images/graemlins/bowdown.gif /ubbthreads/images/graemlins/bowdown.gif /ubbthreads/images/graemlins/clap.gif /ubbthreads/images/graemlins/thumbsup.gif
 
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