Picking a transistor.

[paulca]

So the options that seem to present themselves are:

* to use small NPN transistors in parallel, so each one is only switching <500mA.  It would mean 12 transistors for 4 strips of RGB.
* bin these silly LEDs and just buy the 12V WS2812s, even though I don't need individual (or groups of 3) addressing, they are much easier to deal with.

I might use these elsewhere and just wire 12V to all the pins (or actually 12V to one and ground to the others).

[ledtester]

This Adafruit page suggests using a TIP120 or IRLB8271:

https://learn.adafruit.com/rgb-led-strips/usage

Here's the datasheet for the IRLB8721:

https://cdn-shop.adafruit.com/datasheets/irlb8721pbf.pdf

Looks like it should be able to do at least 1A perhaps even 2A at 3.3V.