Watch comprising sensing and saving means in case of insufficiency of supply source

An electronic watch in which the position of the hands is managed by the electronic circuit for displaying data internal to the circuit, in particular time data. Said watch comprises means for detecting supply insufficiency combined for bringing and maintaining the hands on reference positions when such deficiency is detected, thus avoiding a discrepancy between the indications of the hands and the internal data which they must display when the supply source is back to normal.

In a large number of current electronic watches, there are means for 
detecting insufficiency of the supply source called EOL for &lt;&lt;end of 
life&gt;&gt; which indicate that the battery reaches the end of its life. Such 
detection, essentially based on the measurement of a minimum battery 
voltage, generally generates particular behaviour of the second hand of 
the watch, which is capable of drawing the user's attention to the fact 
that he needs to change the battery as soon as possible. There also exist 
watches including two hands driven by at least one motor wherein the 
position of the hands is controlled by the electronic circuit so as to 
display internal circuit data, for example time data. This is the case of 
the TWO TIMER watch by Tissot, wherein the positions of the hour and 
minute hands have to correspond to an internal electronic counter also 
able to be digitally displayed. The same is true for the displays of the 
chronograph of the watch Swatch Chrono as well as for the watches Stop 
Swatch and Swatch MusiCall wherein the hands can display either the hours 
and the minutes, or an alarm time, or an internal counter. This type of 
arrangement requires perfect synchronisation between the internal 
electronic counters and the movement of the hands on the dial. However, in 
the aforecited watches, this synchronisation can no longer be assured when 
the power supply has been interrupted. Thus it is necessary, for example 
when the battery is changed, to perform a quite complicated hand phase 
setting operation which is not easy for the average user. 
This is not serious insofar as the battery is generally only changed after 
several years, and when said user goes to an approved seller to change the 
battery, said seller himself undertaking the operation. It would be much 
more inconvenient within the scope of watches which are automatically 
recharged by solar cells or a generator. As a matter of fact, this type of 
watch has a much more limited power reserve and it would be very 
restrictive for the user to have to perform this hand phase setting 
operation each time that he put his watch to one side for a few days. 
The object of the present invention is precisely to provide a simple and 
efficient solution to this problem. The invention concerns an electronic 
watch including at least two hands driven by at least one motor, 
electronic means arranged for positioning said hands on the dial so as 
display internal data determined by said electronic means, in particular 
time data, as well as a power source and means for detecting any 
insufficiency of said power source, 
This is not serious insofar as the battery is generally only changed after 
several years, and said user goes to an approved seller to change the 
battery, said seller himself undertaking the operation. It would be more 
inconvenient within the scope of watches which are automatically recharged 
by solar cells or a generator. This type of watch has a much more limited 
power reserve and it would be very restrictive for the user to have to 
perform this hand phase setting operation each time that he put his watch 
to one side for a few days. 
European Patent No. A-591557 concerns an electronic watch including at 
least two hands driven by at least one motor, electronic means arranged 
for positioning said hands on the dial to display internal data determined 
by said electronic means, in particular time data, as well as a power 
source. Detection means supply signals in the event of an insufficiency of 
the power source. During this detection, the position of the hands and the 
value of the corresponding electronic counters are stored in a 
non-volatile memory provided for this purpose. 
European Patent No. A-285838 concerns an electronic watch including at 
least two hands driven by at least one motor, electronic means arranged 
for positioning said hands on the dial to display internal data determined 
by said electronic means, in particular time data, as well as a power 
source. According to this document, detection means supply signals 
corresponding to an insufficiency of the power source. 
The additional functions are then stopped and the minute hand can be 
brought back to the zero position to indicate to the user the End of Life 
(EOL) situation. Conversely, the hour hand continues to display the 
present time. When there is sufficient power again, the radio receiver is 
switched on and the usual initialisation procedure for Junghahs watches is 
performed (hands set at zero, wait to receive a valid time telegram, then 
automatic time setting). 
The object of the present invention is to provide a simple, efficient and 
easily implemented solution to this problem. The invention concerns an 
electronic watch including at least two hands driven by at least one 
motor, electronic means arranged for positioning said hands on the dial so 
as display internal data determined by said electronic means, in 
particular time data, as well as a power source and means for detecting 
any insufficiency of said power source, characterised in that said 
electronic means are arranged so as to bring and keep the set of hands on 
reference positions when said detection means supply signals corresponding 
to an insufficiency of the power source.

FIG. 1 shows schematically and by way of example the circuit of a watch 
according to the invention. This Figure shows a watch 1 including three 
hands 2, 3 and 4, mounted on concentric shafts. This watch includes 
control means in the form inter alia of two push buttons 5 and 6. In this 
description, it is admitted that the different hands 2, 3 and 4 are driven 
independently of each other by their own motor 7, 7' and 7", but the 
invention also applies to watches wherein several hands are driven by the 
same motor as in the TWO TIMER. In the configuration of FIG. 1, each motor 
is controlled by a combination of electronic circuits, 8, 8' and 8", 
arranged for positioning the corresponding hands on the dial so as to 
display internal data, 9, 9' and 9", supplied by the watch counting and 
control circuit 10. At the present time, the set of functions of the 
electronic means shown in FIG. 1 can be realized in sequential logic 
programmed by a microprocessor. They have been shown schematically in the 
form of a combination of circuits in order to facilitate comprehension of 
the invention. 
Counting and control circuit 10 is connected to push buttons 5 and 6, and 
includes a time base regulated by the quartz resonator 11 adjusted by the 
capacitive trimmer 12. The watch assembly is supplied by a power source 
which could be a battery, or a Gold Cap or an accumulator charged by a 
generator or a solar cell battery. FIG. 1 shows this latter solution via 
Gold Cap 13, charged through diode 14 by a group of photovoltaic cells 15, 
generally arranged on the dial of the watch. The counting and control 
circuit supplies data 9 to circuit combination 8 to position hand 2. This 
circuit combination 8 includes a selection circuit 16 whose output is 
connected to a comparator 17 also connected to the output of a logic 
circuit 18 the state of which is representative of the position of hand 2 
on the dial. Comparator 17 is connected to the control circuit for motor 
7, which is itself connected to the input of logic circuit 18. This forms 
a control loop which tends to keep the outputs of circuits 16 and 18 
equal. In the event of inequality, comparator 17 acts on the control 
circuit for motor 7 and on logic circuit 18 to cause them to advance 
step-by-step until equality is re-established between the outputs of 
circuits 16 and 18. Thus hand 2 displays internal data determined by the 
electronic means as they are supplied at the output of selection circuit 
16. Likewise, hand 3 displays data supplied at the output of selection 
circuit 16' via comparator 17' and of logic circuit 18', while hand 4 
displays data supplied at the output of logic circuit 16" via comparison 
circuit 17" and logic circuit 18". Such systems have already been 
described and operate in the watches which were cited hereinbefore. In 
order for the system to operate properly, as already mentioned, the state 
of logic circuit 18 must be, representative of the position of the 
corresponding hand on the dial. Thus if this hand makes 60 steps per 
revolution, logic circuit 18 must have 60 states corresponding to the 60 
possible positions of the hand on the dial, and its 0 state must 
correspond for example to the position of the hand at 12 o'clock (midday). 
In this example, 12 o'clock corresponds to the reference position of the 
hand corresponding to the 0 state of logic circuit 18. This is the 
reference which will be used in the description but any position of the 
hand corresponding to any state of logic circuit 18 can theoretically be 
used as a reference. 
When the circuit is supplied normally motor 7 and logic circuit 18 operate 
in concert, and the synchronisation between the display and the state of 
circuit 18 can be maintained without any problem. This is not so when the 
supply voltage goes below a critical threshold, or disappears. After a 
change of battery, logic circuit 18 is put either in any state or in the 0 
state if a POR (power on reset) is performed. There is often a 
displacement and counter 18 is no longer representative of the position of 
the hand on the dial. The same is true for circuits 18' and 18". In order 
to correct this, a phase resetting operation has to be performed, which 
consists in first bringing the different hands to 12 o'clock, then 
resetting the corresponding logic circuits to 0. This procedure is 
relatively complex and many users do not know how to use it. It will not 
be described in more detail since this type of procedure is known in the 
watches which have been cited. This restriction has little importance in 
the event of a change of battery, since the person who performs this 
operation is supposed to be competent to perform the phase resetting 
operation. It is much more critical in the case described in FIG. 1, where 
the power supply is assured by a Gold Cap recharged by solar cells. It is 
known that the power reserve of such watches is presently only a few days, 
and it is unthinkable for the user to have to go to an approved agent each 
time that he has put his watch to one side a little too long and it stops. 
A way of avoiding this phase resetting of logic circuits 18 and the 
corresponding hands each time would be a setting to 0 when the power 
supply becomes insufficient, but is still high enough to assure operation 
of the motors. This setting to 0 consists in bringing the hands and the 
logic circuits to their reference position, and locking the hands and 
logic circuits in this position, until the power supply becomes normal 
again. This is precisely the object of the present invention. This setting 
to 0 can be very simply performed by blocking the output of selection 
circuit 16 at 0. In order to do this, circuit 16 includes an input 19 
which switches the output to 0 whatever the state of input 9, which brings 
hand 2 to 12 o'clock and logic circuit 18 to 0. Of course input 19 could 
switch the output of selection circuit 16 to any chosen reference value 
other than 0. Selection circuits 16' and 16" include inputs 19' and 19" 
allowing hands 3 and 4 to be set to 12 o'clock. Thus hands, 2, 3 and 4 can 
be set to 12 o'clock either together or separately. 
FIG. 2 shows schematically and by way of example means for detecting any 
insufficiency in the power supply and the electronic means which are 
associated therewith. One sees again in this Figure comparator 17 and 
logic circuit 18 which act on motor 7 so as to control the position of the 
corresponding hand on the dial. Selection circuit 16 is formed of 6 AND 
gates receiving at their first inputs the internal data to be displayed. 
The second inputs of these 6 AND gates are connected to the output of an 
AND gate 20. When this output is at 1, the 6 AND gates are conducting and 
internal data 9 are transmitted to their outputs and thereby to the input 
of comparator 17 so as to be displayed. On the contrary, when the output 
of AND gate 20 is at 0, the outputs of AND gates 16 are at 0. The hand 
driven by motor 7 moves until the state of logic circuit 18 is also equal 
to 0, which corresponds to the positioning of the hand at 12 o'clock. This 
condition is maintained as long as the output of AND gate 20 is at 0. If 
this output again passes to 1, internal data 9 will again be transmitted 
by the output of AND gates 16 to the input of comparator 17 and the hand 
driven by motor 7 returns to the position on the dial corresponding to the 
display of such data. 
The output of AND gate 20 passes to 0 when one or the other of its inputs 
passes to 0. Let us examine the conditions in which this occurs. The first 
input of this gate 20 is connected to the output of an OR gate 21 whose 
first input is connected to a voltage comparator 22 connected on the one 
hand to an internal voltage reference 23 and on the other hand to a 
network of resistors 24, 25 and 16 connected to the terminals of the power 
supply. When the voltage of the power supply is correct the output of 
voltage comparator 22 is at 1. When this voltage goes below a first level, 
the output of voltage comparator 22 passes to 0. The two other inputs of 
OR gate 21 are connected to the contacts of push buttons 5 and 6. These 
inputs are normally at 0 when these contacts are open and momentarily pass 
to 1 when the user presses them. 
Let us assume that the second input of AND gate 20 is at 1 and contacts 5 
and 6 are open. When the power supply has a sufficient voltage, the output 
of voltage comparator 22 is at 1 as is the output of OR gate 21 and the 
output of AND gate 20. The hand driven by motor 7 displays data 9. When 
the voltage of the power supply passes below a first level, the output of 
voltage comparator 22 passes to 0, as do the outputs of gates 21, 20 and 
16, and the hand driven by motor 7 is positioned at 12 o'clock and stays 
there. However, the user has only to press on one of pushers 5 or 6 for 
the output of gates 21 and 22 to pass to 1 again and for the correct 
display of data 9 to be re-established. This is an intermediate situation 
in which the hands are brought to 0, which allows the user's attention to 
be drawn to the fact that the power supply is becoming insufficient, while 
allowing him momentarily to re-establish the correct display of his watch 
by pressing on one of the push buttons. In the particular case in which 
one of the hands, for example hand 4, is used for indicating the seconds, 
one could simply give a particular movement to this second hand in this 
intermediate situation, or bring only this second hand to 0. In the case 
described it will however be assumed that the three hands are reset to 0. 
Let us now consider what happens at the second input of AND gate 20 
connected to terminal S and at the output of the three input AND gate 26. 
The first input is connected to a safety contact 27 whose utility will be 
explained with reference to FIG. 5. When this contact is open, the output 
of AND gates 26, 20 and 16 pass to 0. The display is set to 0 and the 
hands are positioned at 12 o'clock. The two other inputs of AND gate 26 
define conditions which can either be cumulated as is the case here, or 
used in isolation. The second input of AND gate 26 is connected to the 
output of a voltage comparator 28 one input of which is connected to 
voltage reference 23, and the other is connected to the network of 
resistors 24, 25 and 26. When the power supply voltage is sufficient, the 
output of voltage comparator 28 is at 1. When this voltage passes below a 
second level, this output passes to 0, as do the outputs of AND gates 26, 
20 and 16. The display is set at 0 and the hands are positioned at 12 
o'clock. Finally the third input of gate 26 is connected to the inverting 
output of a delay line 29 formed for example by a shift register which 
receives pulses every 12 hours at its clock input from the counting 
circuit. This register 29 is maintained at 0 as long as the output of 
voltage comparator 22 is at 1 and becomes active when it passes to 0, i.e. 
when the power supply voltage passes below the first detection level. When 
the delay fixed by the shift register is reached, its inverting output 
passes to 0, as do the outputs of AND gates 26, 20 and 16. The display is 
set at 0 and the hands are positioned at 12 o'clock. It is to be noted 
that the conditions which determine the passage to 0 of the output of AND 
gate 26, which causes the display to be set to 0 and the hand to be kept 
at 12 o'clock, cannot in any event be cancelled by pressing push buttons 5 
or 6, as is the case found in the intermediate situation. If his watch is 
supplied by a battery, the user is obliged to change it. In this case the 
behaviour of his watch during the intermediate situation should have 
attracted his attention and allowed him to change his battery before his 
watch became completely blocked. If his watch includes a system for solar 
cell or generator recharging, he must either expose it to light, or impart 
sufficient movements of rotation thereto. In these two latter cases, the 
passage through the intermediate situation is not indispensable seeing 
that the user can re-establish a normal situation himself without going to 
an agent. It is to be noted that the electronic circuit of the watch 
continues to operate at a much lower voltage than the motors. Thus the 
correct display of the watch can be found again, even if it has been 
completely blocked, which will be discussed with reference to FIG. 3. 
FIG. 3 shows schematically and by way of example the different operating 
zones of the means of FIG. 2. Let us assume that the watch is supplied by 
photovoltaic cells with a nominal voltage of 1.6 volts, and that there is 
a first detection level at 1.15 volts. Moreover, the circuit consumption 
is 0.2 .mu.A and that of the motors is 0.6 .mu.Coulomb per step. These 
motors operate correctly to 1 volt. For a watch which beats the seconds, 
the total consumption is 0.8 .mu.A. In a conventional watch, this 
consumption is constant and remains even when an insufficiency is noted in 
the power supply and the EOL (end of life) system is operating. Thus the 
Gold Cap which assures the power reserve will continue to be discharged at 
the same rhythm and the watch will stop after a few hours. 
In our case, it can be seen that there is a first zone 1 where the normal 
operation of the watch is assured. Then, between detection levels 1 and 2, 
there is a zone 2 where at least the second hand, or the set of hands, is 
blocked at 12 o'clock. Although the user can re-establish the normal 
display on demand, the average consumption of the motors becomes very low, 
and the consumption of the whole of the watch is brought to 0.25 .mu.A, 
i.e. a reduction of more than three times. This means not only that the 
discharge of the Gold Cap will be slowed down by the same factor, but that 
three times less illumination of the photovoltaic cells is enough to 
stabilize the voltage and maintain the watch in this state. When the 
voltage passes below the second detection level, one passes to zone 3 and 
all the hands are blocked at 12 o'clock. All that remains is the circuit 
consumption of 0.2 .mu.A. In this zone, the operation of the motors could 
no longer be assured and a conventional watch would lose time 
definitively. In our case, the hands are blocked in known positions and 
the consumption is reduced to the maximum, but the electronic circuit 
continues to assure its different functions, particularly its time 
functions. It is known that present CMOS low voltage circuits can 
currently operate at up to 0.8 volts. NEC has even announced circuits 
operating at 0.4 volts. Thus, if the power supply voltage increases from 
zone 3 to the higher zones, the correct display of the functions by the 
hands is automatically re-established. In zone 3, as in zone 2, very low 
illumination of the photovoltaic cells is required to stabilise the 
voltage and maintain proper operation of the circuit functions. If 
however, the voltage continues to decrease, one enters zone 4 where the 
circuit can no longer assure these functions. When the voltage increases 
to its normal level, the time of the watch will therefore have to be 
reset. Conversely, in this zone 4, the logic states of circuits 18 
representative of the position of the hands on the dial can be preserved, 
and it will not be necessary to perform the phase setting procedure when 
the voltage is restored to normal. If however the voltage continues to 
decrease and one passes into zone 5, one can no longer guarantee that the 
logic states of circuits 18 will be kept. Of course all the hands are at 
12 o'clock, but circuits 18 are highly likely not to be in the 
corresponding state when the voltage increases again. It is thus necessary 
to introduce a POR (power on reset) procedure, i.e. a procedure for 
setting these logic circuits 18 to 0 when the voltage increases, which 
must take into account that the voltage may increase very slowly. This is 
what will be seen in the following Figure. 
FIG. 4 shows schematically and by way of example a circuit allowing the 
means of FIG. 2 to be placed in the correct starting conditions when the 
power supply is re-established. One sees again in this Figure motor 7, 
logic circuit 18 whose state is representative of the position on the dial 
of the hand driven by the motor, and comparison circuit 17. Terminal S 
corresponding to the output of AND gate 26 of FIG. 2 is connected to a 
first input of a NOR gate 40 whose output is connected to the reset inputs 
of circuits 17 and 18. When the power supply voltage is correct, terminal 
S is at 1 and the output of gate 40 is at 0. When one passes into zone 2 
of FIG. 3, terminal S passes to 0. The logic outputs representing the 
state of circuit 18 are connected to an OR gate 41 whose output is 
connected to the second input of NOR gate 40. If the state of circuit 18 
is different to 0, the output of OR gate 41 is at 1 and the output of NOR 
gate 40 remains at 0. The fact that circuit 18 is not at 0 means that the 
hand has not yet reached the 12 o'clock position at which it should become 
blocked. As soon as it reaches this position, the state of circuit 18 
passes to 0. The output of OR gate 41 passes to 0 and the output of NOR 
gate 40 to 1. Circuits 17 and 18 are then blocked at 0 as is the entire 
control loop which determines the sending of pulses to the motor. One must 
pass back into zone 2 for terminal S to pass to 1 again and for this 
blockage to disappear. Now, what will happen if the power supply voltage 
goes down to zone 5, or even passes to 0 during a certain period of time. 
In that case, circuits 17 and 18 must be reset to 0 when the voltage is 
restored, so as to prevent these circuits being placed in an undetermined 
state. In order to do this, the output of gate 40 is connected by a 
current source of very low intensity 42 and a capacitance 43 to the 
positive supply pole. These two elements allow the reset inputs of 
circuits 17 and 18 to be forced to 1 when the voltage is restored and to 
set them to 0 before normal operation of the electronic circuits is 
re-established. Thus logic circuit 18 is set in the 0 state corresponding 
to the 12 o'clock position of the hand and it is not necessary to perform 
the phase setting procedure. 
FIG. 5 shows schematically and by way of example a safety device allowing 
the position of the hands to be blocked when the battery is changed. It 
has been shown that it is possible to keep logic circuits 18 in phase with 
the hands by bringing them to 12 o'clock and blocking them there. But what 
happens if the battery is disconnected while the voltage is still 
sufficient. The hands will not have time to move to the correct position 
and synchronisation will be lost. In order to prevent this, one can use a 
safety contact such as contact 27 of FIG. 2, which must compulsorily be 
opened before the battery can be disconnected. Thus one indicates to the 
circuit that the power supply may disappear rapidly, and the circuit is 
left sufficient time to bring the hands into the 12 o'clock position. FIG. 
5 shows battery 50 connected to printed circuit 51 by a contact spring 52 
fixed by means of a screw 53 which is screwed into an insulated case 54. 
Screw 53 is covered by a second contact spring 55 fixed by screw 56. 
Contact spring 55 is arranged so as to establish an electric connection 
between the+pole of the battery and a contact zone of printed circuit 51 
situated under the head of screw 56, via contact spring 52 and the head of 
screw 53. It can easily be seen that if one wishes to disconnect the 
battery, screw 56 must first be unscrewed and spring 55 removed. Doing 
this interrupts the connection between the contact zone of the circuit and 
the+supply pole. This combination acts as safety contact as described in 
FIG. 2. When the battery is put in place, the hands remain blocked at 12 
o'clock until contact spring 55 has been put in place. When the battery is 
removed, contact 55 must first be removed, which allows the hands time to 
move into the 12 o'clock position, before the battery can be disconnected. 
Numerous other combinations implementing the present invention exist, but 
the description thereof would add nothing to comprehension of the 
invention.