Building a red Cree Module

[AardvarkSagus]

I am looking to build a red cree module with THIS led and a generic 1 stage P60-ish drop in that I purchased in the past. Am I correct in assuming that all I really need to do is find the correct value resistor to reduce the voltage being supplied to the LED? If so, what resistor should I look for?

Please correct my possibly mistaken thinking. I'm not well versed in electronics.

Thanks in advance.

 

[baterija]

The red cree has a lower VF than then typical white XR-E so direct drive with a limiting resistor might not be a very good solution. You're probably looking at below 3 volts Vf at max current. Even using one Li-ion you've got pretty a big voltage differential. Using 2 RCR123's you'd be close to double the voltage you need. This is probably a better case for a buck driver. Not sure what would fit a P60 size module though.

For using a resistor here is a handy calculator.

 

[AardvarkSagus]

I am already assuming there is some kind of buck driver in place in this module already since the input voltage was specified as 3.6-9v if I remember correctly. 9v would fry a XR-E pretty quick. I haven't measured yet, but I am guessing I just need a resistor to get from ~3.6v down to the ~2.2.

 

[poguy]

I have used DX constant current regulators with red led's before and it works OK. Pick a regulator that provides the right amount of current and go for it.

 

[AardvarkSagus]

I have used DX constant current regulators with red led's before and it works OK. Pick a regulator that provides the right amount of current and go for it.

Did you just run it straight up or resistor it? I believe that I need a 2-ish ohm resistor in series to make it work.

 

[poguy]

Dropping resistor vs. constant current regulator depends on tolerance for change in brightness as battery runs down and voltage changes. Also the regulated version is often good for a much wider range of input voltages.
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And the dropping resistor is cheap and simple. Take your pick.