I have the following circuit to adjust the speed of a DC motor based on PWM signal (Arduino, 5V) applied to the base of a BJT transistor, but it's not working. The motor doesn't move but I do hear a faint of buzzing sound from the inside.
The PWM is working just fine, I tested it out with an LED + current limiting resistor. The motor works OK when I make a short between transistor's collector and emitter.
Anybody knows what's the problem with the circuit? How can I fix this?
- Q1 is an NPN BC547 transistor.
- PWM signal comes from a 5V pin of an Arduino board.
- Please check the 9V motor's spec here.