pls help

[toeb]

i'm in my final year studying electrical electronics. And my final year project is tagged .multi-fan digital control panel with wireless remote control. my design of the control panel has a simple interface. it will have just 7 buttons and a lcd display. a backward and foward button for fan toggling and the remaining five buttons for speed regulation. i intend to use relays for fan switching and speed switching but i have a problem each fan is to have variable speeds. how do i make this happen with a single tap changing transformer even though i hav accounted for the total power required

 

[whiz115]

usually for good and power efficient speed control they use PWM but i don't know what exatly you should do.