For experiments with a disk rotating at various speeds, the April 1998 Electronics Now magazine suggests this PWM motor control. The current with the LM317 is 1.5A maximum.
The circuit in the figure can be used to trigger a triac or even a comparator in a project that...
Suggested by a 90s Electronic Design, this circuit drains only 0.25 mA from its source. Listening...
Found in a 1960 Sylvania manual, this circuit can be implemented with a modern equivalent...