Device comprising a solar cell for winding a barrel spring

A barrel-spring winding device comprising:

• a capacitor;
• a solar cell arranged to receive ambient light and to charge said capacitor;
• a control circuit connected to terminals of the capacitor;
• and
• a motor connected to said circuit and having a rotor operatively connected to wind the spring,
• wherein said motor is a stepping motor having two terminals and the control circuit comprises:
• means for supplying a drive signal having two states, a first state produced in response to a parameter representing the state of charge of the capacitor, and a second state produced after a given period of time from the beginning of the first state;
• and
• means for connecting said motor to the terminals of the capacitor in response to the first state of the drive signal and for disconnecting the motor from the capacitor in response to the second state of the drive signal
• said means for supplying said drive signal comprising:
• means for comparing said charge parameter to a reference value and producing a triggering signal when said charge parameter is substantially equal to the reference value;
• means for producing a pulse in response to said triggering signal, said pulse having a duration equal to a second period of time at least equal to the time needed by said rotor to make on complete step to prevent the motor from being connected to the capacitor before it is stopped;
• and
• means for producing a bi-level logic signal in response to said pulse, the level of said logic signal at the beginning of the pulse corresponding to the first state of the triggering signal and its other level corresponding to said second state of the triggering signal.

A barrel-spring winding device, comprising:

• two capacitors;
• a solar cell arranged to receive ambient light and to alternately charge said capacitors;
• a stepping motor having a rotor operatively connected to wind the spring;
• means for comparing a charge parameter of each capacitor with a reference value and producing a triggering signal when the charge parameter of one of the capacitors is substantially equal to said reference value;
• means for producing a pulse in response to said triggering signal, said pulse having a duration equal to a period of time which is at least equal to the time needed for the rotor to make a complete step to prevent the motor from being connected to one of the capacitors before being stopped;
• means for producing a logic signal in response to said pulse, said logic signal passing to a first level at the beginning of the pulse and to a second level at a subsequent period of time;
• connection means for selectively connecting the motor to one of the capacitors and connecting the cell to the other capacitor;
• and
• switching means for controlling said connection means, in response to said pulse, said logic signal and the values of the charge parameters of the capacitors, so that the motor is connected during said subsequent period of time to whichever of the capacitors has a charge parameter substantially equal to said reference value, and the cell is connected to the other capacitor until the charge parameter of said other capacitor has reached the reference value.