How to connect a bare 5050 SMD LED to 3.3v

Other Hardware LEDs and Multiplexing
1

I just ordered some WS2812B LEDs, but I don't have any on hand. I do have a 5050 SMD RGB LED that came in a 37-in-1 sensor kit I bought a while back, but I'm not sure how to hook it up to my hardware which is 3.3v (A Sparkfun Thing).

The 5050 I have is mounted on a small PCB with 4 male header pins. (B, R, G, -). There are no capacitors or resistors on this board. If any are needed I will have to install them myself.

I saw that there should be limiting resistors connected to this 5050 when connecting to a 5v source. Can anyone tell me if limiting resistors are necessary if connecting to 3.3v?

Also, if limiting resistors should be used at 3.3v, what values should I use to enable me to get the most brightness without damaging the chip?

It looks like there is 5050 documentation here: http://www.tweaking4all.com/wp-content/uploads/2014/01/5050LED.pdf - except that I'm not sure how to read the requirements.

I was intending on using pins 4, 12, 13 with PWM for the RGB pins.

I appreciate any help.

2

Yes you need current limiting resistors.

The value depends on how much your pin can provide. A 3V3 Arduino does not narrow it down sufficient to say.

3

How do you fill a bucket of water when the tap is the same hight as the bucket.

If you have 5volt available, connect the LED/resistors to 5volt, and let the 3.3volt Arduino switch to ground.
With transistors (fets) if the LED current is too high for the pin.
Leo..