Micro electric drill motor automatic speed regulation circuit

Circuit working principle: When the motor is no-load, changing its operating voltage can change
the motor's speed. At this time, the change in current is very small. When the motor is loaded,
its operating current will increase rapidly, and the increase in current has almost nothing to do with the operating voltage
, and the increase in current is several times or even dozens of times that of the no-load state. From this, we can determine whether the motor
is loaded by detecting the operating current of the motor , and then use the change in current to control its operating voltage.