The circuit depicted below showcases a flexible and adjustable variable-voltage speed control mechanism. This control is achieved by utilizing a variable potentiometer, RV1, in conjunction with a TIP122 power transistor. A TIP122 transistor is a type of bipolar junction transistor (BJT) that is commonly used to drive high-power DC motors.This combination allows for the modulation of the motor's DC voltage across a range from zero to 12 volts.
By employing this specific circuit configuration, a satisfactory level of speed control and self-regulation can be achieved when operating the motor at medium to high speeds. However, it is important to note that this circuit design exhibits significant drawbacks in terms of controlling the motor at low speeds. It also exhibits slow-start functionality, which may not be suitable for certain applications requiring quick initiation.
Below picture shows TIP122 transistor.
As a result, this type of circuit is primarily utilized in speed-control applications that have limited-range requirements. In scenarios where precise low-speed control and rapid start-up are crucial, alternative circuit designs would be more suitable.
Other methods for DC motor control are below.
[1] Arduino Nano with TIP122 DC Motor speed Control
[2] Joystick controlled DC motor with Arduino and TIP122
