Abstract: A method of controlling a stepping motor comprises supplying the motor with a predetermined quantity of energy E.sub.io from whence there will result an automatic adaptation of the width of the motor drive pulse to the voltage U.sub.o at the motor terminals and the resistance R.sub.i of the energy source. At the moment when the internal energy E.sub.i (t) supplied to the motor, as defined by the integral over a time period of the product of U.sub.o -RI and the current I.sub.t circulating in the motor winding, becomes equal to E.sub.io the drive pulse is cut off (R is the resistance of the motor winding). The circuit for practicing the method according to the invention includes means for measuring the voltage U.sub.o and the energizing current I(t), means for obtaining the difference U.sub.o -RI, a multiplier for forming the product (U.sub.o -RI)I(t) and an integrator the output of which provides a voltage proportional to the internal energy E.sub.i (t).

Abstract: The stepping motor (1) is provided with magneto-mechanical means (11) in order to reverse the rotation sense of its rotor (2). When the magnetic element (12) is withdrawn or flush with the gap (3), the rotor turns in the sense of the arrow (27). When such element is extended into the gap through application of pressure to the push-piece (14), the rotor will turn in the sense opposite to that of the arrow (27).