First of all I am asking this question out of curiosity, I have no knowledge of electrical devices other than understanding of few terms that I learned in school. I am planning to work on home automation project but before that trying to figure out what I need, to do what I want to do. I saw some automation videos using Raspberry Pi and relay modules, after watching those videos I was sure I can use a Raspberry Pi with 5V relay board. I watched some more videos and from those videos I learned few things that relay needs 5V input but output of GPIO is 3.3V.
Now my confusion/concern is that is 3.3V enough to power/control 4 or 8 or 12 relay simultaneously?
Some posts suggests remove jumper on relay board and use of external 5V power supply to power relay than powering it from Pi, some suggest to modify relay board like this one, some even suggest to connect 5V of Raspberry Pi to VCC of relay and GND from Pi to GND of relay.
These posts and videos left me confused weather I can use Raspberry Pi with 5V relay board without any modification to relay board or supplying external power to it.