I am currently a computer engineering student trying to build a simple circuit to vary voltage by using a transistor and a arudino uno. The motor draws between 12v and 28v with a current of about 280mA. I want to control the voltage using the arduino thru the use of PWM from the arduino. So in theory a 50% duty cycle of the arduino will give me half the voltage from collector to emitter. I tried using PWM without any capactiors and it ended up making the motor whine and might end up damaging it.
The BJT that I will be using is the TIP120 with a beta of 1000.
Here's the schematic, I originally tried using a 1nF capacitor across the motor to try to smooth out the voltage during the off cycle of pwm. But that still made the motor whine so I tested a bunch of different capacitors and about 10uF made it quieter but both the power supply and the motor both whined.
How would I be able to get a consistent line at 12v? or any other voltage as set by the duty cycle.
PS the inductor is the motor and the values are not correct. Just used as a reference.