Using PWM allows precise current control in the windings. Hence, the output torque, which is linearly proportional to the average winding current, can be correctly controlled in coreless motors.

Motor speed can be adjusted by the light intensity falling into the photoresistors LDR1 and LDR2. These resistors control the bias points of two transistors connected via an input inverting buffer ...

It’s an excellent way to learn about both PWM motor control and the use of 555 timers, all with a very low parts cost and readily available components. We’ve seen such setups before, used as ...