When is it necessary to use a resistor?

[cartermaneki]

(Sorry for all the silly questions as of late) So at the moment I'm working on various laser projects, and I was wondering when a 4.3 ohm resistor is necessary. I'm working on a 300mW infrared laser that has a Aixiz driver wired to the diode and before I fire it up (and possibly give it too much current) I'm asking if I'll need a resistor, or can I just go without? Any and all feedback is appreciated.

 

[marcuspeh]

Dont use a infared laser for your first build. Use something of a visible wavelength. As for your question, since you are planning to use 808nm for your fist build, it is not necessary to answer it.

 

[cartermaneki]

Well, I have a 405nm that I'd love to wire up, but I cannot figure out the pin configuration. It's a Sony SLD3235VF, if someone can help me figure out the pinning I'd be all for build one of those.

 

[marcuspeh]

This should be the pinout for it.

As for your question, the aixiz driver current can be set. So there is no need for a resistor. Get a testload and you can set the current by turning the pot.