Timepiece with a device for the control of a stepping motor

DETAILED DESCRIPTION The object of this invention is to correct these defects by providing a control device in which the energy of the driving pulses depends directly on the time taken by the rotor to effect all or part of a step, this energy being matched to each step in relation to changes in the time required for its performance.
By making the performance time equal to a value which is judiciously chosen in relation to the motor type, the moment of inertia of the rotor, the starting torque, etc.
, by means of a control circuit, changes in the motor load are taken into account at all times while a virtually constant safety margin is maintained, even when there are rapid variations in the load.
Mechanisms, date indicating devices, contacts, etc.
can therefore be operated without danger and without disturbing the system.
Except in exceptional cases it is not therefore necessary to provide making up impulses, even if the safety margin is set very low, e.
g.
only 10% above the operating limit of the motor.
According to the present invention there is provided a timepiece with a device for the control of a stepping motor, comprising an oscillator, a frequency divider connected to the said oscillator for delivering a plurality of control signals, a control circuit which is connected at least indirectly to the said frequency divider for delivering driving pulses to the said motor, wherein the device for the control of the stepping motor is associated with a detector which delivers a signal when a particular point in the characteristic of the current in the motor winding is reached, the appearance of this point being related to the time taken by the rotor to make one step, this time being variable as a function of load, the said timepiece also including means to vary the energy supplied to the said motor by the said driving pulses as a function of variations in the time of the appearance of the said signal in relation to the driving pulse.