user34176: I am new to Arduino and I am just playing with it, I wanna control a 48,000rpm motor with 9v voltage via Arduino the plobrem is how could I make that motor slow down, slowly. Any ideas? I am using Arduino mega

user19409: So far you haven't added any information about the motor so I am going to assume it is a standard DC motor.
With this type of motor, you can change the speed by varying the voltage. So at 9V it will go full speed (theoretically 48,000 RPM). At 4.5V it should go at about (roughly) half. Of course this varies with the load you are applying to the motor.
You can control the motor speed using the PWM output of the Arduino. If you would like to read more about Pulse-width Modulation (PWM) I highly recommend that you read the Sparkfun article here.
This presents 2 problems.

The Arduino Mega PWM only gives you an adjustable voltage between 0V to 5V.
The current provided on these pins is only small and would not be able to power the motor fully.

To overcome both you need to add a MOSFET. I suggest a N-Channel MOSFET that switches on the low side.

simulate this circuit – Schematic created using CircuitLab

34176: <p>I am new to Arduino and I am just playing with it, I wanna control a 48,000rpm motor with 9v voltage via Arduino the plobrem is how could I make that motor slow down, slowly. Any ideas? I am using Arduino mega</p>
 19409: <p>So far you haven't added any information about the motor so I am going to assume it is a standard DC motor.</p>

<p>With this type of motor, you can change the speed by varying the voltage. So at 9V it will go full speed (theoretically 48,000 RPM). At 4.5V it should go at about (roughly) half. Of course this varies with the load you are applying to the motor.</p>

<p>You can control the motor speed using the PWM output of the Arduino. If you would like to read more about Pulse-width Modulation (PWM) I highly recommend that you read the Sparkfun <a href="https://learn.sparkfun.com/tutorials/pulse-width-modulation" rel="nofollow noreferrer">article here</a>.</p>

<p>This presents 2 problems.</p>

<ol>
<li>The Arduino Mega PWM only gives you an adjustable voltage between 0V to 5V.</li>
<li>The current provided on these pins is only small and would not be able to power the motor fully.</li>
</ol>

<p>To overcome both you need to add a MOSFET. I suggest a N-Channel MOSFET that switches on the low side.</p>



<p><img src="https://i.stack.imgur.com/iTt71.png" alt="schematic"></p>



<p><sup><a href="/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fiTt71.png">simulate this circuit</a> &ndash; Schematic created using <a href="https://www.circuitlab.com/" rel="nofollow">CircuitLab</a></sup></p>
