Typically the output of an Arduino type board does not have sufficient current to drive an LED so you need a driver circuit using a transistor.  Here is a fritzing diagram and a schematic of how to wire up a simple driver circuit. A more complicated multiple LED driver circuit can be found in the documentation for IRLib2. 

The base of the transistor is connected to pin 9 of the feather board (or pin 6 of the MKR 1000)using a 470 ohm resistor. The emitter is connected to ground and the LED is connected between the +3.3V and the collector.

The MKR1000 uses pin 6 as its default output pin rather than 9 on the Feather. These defaults can be changed in IRLib2. See it's users manual for details.

This guide was first published on Mar 12, 2018. It was last updated on Mar 12, 2018.
This page (Wiring) was last updated on Aug 05, 2020.