FR2521741A1 - Clock seconds indicator stepping motor synchronisation - by using quartz oscillator and opto-electronic zero position detection - Google Patents

Abstract

The second handcoherence of the clock is controlled in with electrical pulses received by the clock indicator each minute from a pulse generator, galvanically isolated. The second hand is mechanically coipled with a disc allowing its detection in the zero position by means of an opto-electronic pick-up. An electronic rocking lever stops the operation of the quartz oscillator when a pulse representing the passage of the second hand through the zero position, is received from the opto-electronic pick-up. The oscillator begins operating again when the minute pulse from the pulse generator arrives at the rocking lever. Divider stages secure, starting from the quartz frequency, the frequency of 1KHz required to control the second hand. The 1KHz pulses are then transferred to an amplifying system which transforms them into polarised voltage and current pulses necessary to drive the stepping motor.

Description

 The present invention consists in obtaining synchronization of the display of the seconds by an electrical pulse occurring at regular time intervals.

 The invention relates more particularly, but not exclusively, to "second" stepping motors intended for clocks.

 In common devices of this kind, the second hand is controlled by a synchronous motor and describes a rotation of 3600 in less than a minute, it stops at the Zero position and resumes its cycle after a time of very noticeable stop when passing the minute pulse.

 The disadvantage of this system is to give erroneous time information, and to cause a stop of the "second" hand for several seconds each minute. This type of registration indeed requires a permanent advance of the "second" hand in real time to allow a certain restart at the passing of the minute.

 To overcome this drawback, the first object of the invention is to electronically synchronize the display of the seconds with a minute pulse every 60 seconds.

Another object of the invention is that there is no perceptible stopping of the hand or any other display of the seconds in normal operation.

 To achieve these goals, the first characteristic is to use a quartz oscillator to guarantee high precision.

The second characteristic consists in being able to reset to zero the quartz oscillator by a minute pulse and to detect the position of the hand or any other display of the seconds by an optical or electrical system.

 The invention will be better understood on reading the description which follows and the attached drawing.

 The attached figure shows the block diagram of a system allowing for example to control a second second hand 9 of a receiving clock, in accordance with pulses received by the receiving clock every minute or a minute, these same pulses being shaped and galvanically isolated by device 5.

 The second second hand 9 is mechanically coupled with a disc which allows detection in the high position. Thanks to the device 7, the detection is preferably carried out by an opto-electronic sensor, but can be carried out by another electrical device.

 The electronic rocker 6 makes it possible to stop the operation of the quartz oscillator 10 when the impulse supplied by 7 arrives, this impulse being the image of the passage of the second hand in the high position.

The oscillator 10 starts again when the minute pulse supplied by the flip-flop 6 arrives. The dividing stages constituted by the assembly 4 make it possible to obtain from the quartz frequency, the frequency of 1 Hz necessary driving the second hand. The pulses of 1 Hz obtained are then transferred to the amplification system 3 which transforms them into polarized pulses of voltage and current necessary for controlling the step-by-step movement 8 driving the second hand 9.

 The crystal oscillator is adjusted so that a total drift of 60 ms over one minute is obtained.

It follows that the second second hand will always go high 60 ms before the arrival of the minute pulse. In normal operation, said second hand will therefore observe a pause of 60 ms each minute, which is not visually discernible and ensures sufficient precision in most applications
In this application example, the power supply is provided by the devices 1 and 2.

 The present invention applies more particularly but not exclusively to clocks with analog or digital display. It can also apply in the case of a timing device.

Claims (2)

 1 - Electronic device allowing the control of an electromagnetic stepper motor causing the display of the seconds of a clock, synchronized by an external electric pulse, characterized by the control of the stepper motor using a system electronics controlled by a quartz oscillator.  2 - Device according to claim 1, characterized in that it allows to localize the zero position of the second needle by an optical or electrical detection system.