Sonoff IR remote controll extension for Sonoff-Tasmota and iTead Sonoff Basic.
The resistor values depend on the used IR LED and the gain of the NPN Transistor. Rb is not really necessary an can be left out. R1 limits the current through the diod and can have Values between 2.5 Ohm and 10 Ohm. Using lower values gives you a better range but you risk the diod if the current gets to high. About 100mA are ok for sending signals. Check your datasheets!
The diode is facing upwards, the rest downwards. The board directly fits onto the Sonoff pinheader used for programming and uses GPIO14.