How to control fan speed 220v using arduino?

Question

PHP

There is a relay 220 connected to the arduino, is it possible to control the speed of the fan connected to it?

Answer 1

$ids = explode(',', $arr['ids']);

$newArr = array_map(function($n, $i) use($arr) {
  return [ $n, $arr['src'][$i] ];
}, $ids, array_keys($ids));

Answer 2

Well, the relay itself cannot control the speed of revolutions.
And in general - whether it will work in principle - depends on the type of fan motor.

Answer 3

Try a semister (triac)