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.
Two transistors on a regenerative switch are used to trigger a triac. This circuit is from the RCA...
This circuit uses a 555 (according to the diagram) to generate 50 ms tone bursts at a frequency of 1.5...
The radio presented was found in a 1980 documentation. It consists of 3 stages: the tuning circuit...