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.
This circuit that draws 1 out of 8 LEDs was found in an 80's American documentation. The circuit...
This protective circuit for power lines was found in a Radio Electronics from November 1957. The...
In figures 1 and 2 we have two current drains that can be made with operational amplifiers and...