The amplitude of a swing powered by an electric motor is controlled by detecting a peak voltage induced in the motor coil by the swing motion when the motor is not being powered and comparing the detected voltage with a one of a set of pre-measured reference values of peak voltages obtained at corresponding amplitude settings to provide a signal to a motor controller which adjusts the power supplied to the motor to bring the swing amplitude to. The motor controller supplies a PWM signal voltage to power the motor and adjusts the voltage on-time to bring or restore the swing to the selected amplitude.