I try to regulate a 12V into 3.7V using an LM317 voltage regultor.
I used R1=220Ohm and R2=470Ohm, using this circuit:
It regulates a 3.9V (close enough for me,) but it heats up. I can't even touch it while it is powering an ESP8266 ( which draws a max of 200mA.)
Why is it getting hot?