555 PWM motor speed controller

Here is a project I did after the arduino PWM motor controller.

A 555 timer doesn't have enough power output to drive a motor alone, so a TIP120 transistor is used as a gate for the power source (a 9V battery).

I wanted to adjust the motor speed live, so I used a potentiometer to vary the duty cycle. 

Here is the schematic:

This is my working breaker board:

Here are the oscillograms, with blue across the motor leads and the red across the 555 time output.

For the calculations, I used the calculator found here:

http://www.ohmslawcalculator.com/555_astable.php