ferkheusa:
Could you please tell me how can I get the 3.3v value from Arduino Uno to turn on and off. I wanted to turn it on and off to stop a pump. The pump requires between 2.8v and 3.3v to turn it off and 0v to turn it on.
How much current does this pump require? You can't turn the 3.3V pin on and off, that's straight off a voltage regulator. As ferkheusa said, a diode or two would drop the voltage from a regular pin (since a diode has around a 0.7V voltage drop across it).
Or a resistor and a zener diode could do it. But this is just for low-current (like a pump switching circuit) not the motor itself.