EP0674247A1 - Clock with manual control - Google Patents

Abstract

This watch (1) comprises a case (2), a glass (3) and at least one manual control device (22), which comprises a capacitive sensor (20) with a first electrode (5) arranged on the internal face ( 6) glass (3). The selective positioning of a finger (10) of a watch wearer (1) on the outside face of the glass (3) makes it possible to form a first capacitor (Cd) between the first electrode (5) and the mass (11 ) constituted by the housing (2). A parasitic capacitance (Cp) is present between the first electrode and the housing. The manual control device (22) further comprises a voltage-frequency converter (22) whose oscillation frequency is determined by the first capacitance (Cd), when this is formed by the presence of the finger, in combination with parasitic capacity (Cp). The invention can be used in so-called "handwriting recognition" watches. <IMAGE>

Description

The present invention relates to watches comprising a manual control device and, more particularly, to watches comprising a capacitive sensor, a first frame of which is arranged on the inner face of the watch glass, a first capacity being formed between the first electrode and the mass formed by the housing when a wearer of the watch places a finger on the outside of the watch.

Watches are already known which include manual control devices intended to replace the usual external control means such as push buttons, used to control the various functions of a watch such as setting the time or switching on and off. trigger of a chronograph. Some of these devices consist of at least one transparent electrode placed on the inner face of the watch glass, the latter comprising a circuit arranged so as to exploit the signals which are generated when the wearer of the watch places his finger on the glass. next to this electrode.

Such a device is described in patent CH 607 872. In the arrangement described in this document, a conductive layer is arranged on the inner face of the watch glass in order to form a capacitive sensor. This sensor forms with an independent capacitor a capacitive divider. A high frequency alternating voltage is applied to this divider by a generator. A detection device detects the potential between the independent capacitor and the capacitive sensor. Depending on whether a finger is placed on the glass or not, this detected voltage varies between two values. A comparator compares this detected potential with a reference voltage and therefore provides a control signal having either a logic state high, or a low logical state depending on whether the finger is present or not.

où U_in est la tension appliquée au diviseur capacitif par le générateur, C_p est la capacité parasite, C_d est la capacité du capteur capacitif et C_ref est la capacité du condensateur indépendant.However, a parasitic capacitance is always present between the conductive layer disposed on the watch glass and the mass formed by the case. This capacity is connected in parallel to the capacitive sensor. The potential U _out detected by the comparator can therefore be expressed by the relation $${\text{U}}_{\text{out}}{\text{= U}}_{\text{in}}{\text{(VS}}_{\text{ref}}{\text{)/(VS}}_{\text{p}}{\text{+ C}}_{\text{d}}{\text{+ C}}_{\text{ref}}\text{)}$$

where U _in is the voltage applied to the capacitive divider by the generator, C _p is the parasitic capacitance, C _d is the capacitance of the capacitive sensor and C _ref is the capacitance of the independent capacitor.

Such devices have the disadvantage that, to give them an acceptable resolution, the capacitances C _d and C _ref must be significantly greater than the parasitic capacitance, which leads to a high current consumption, notably reducing the service life of the watch battery. In addition, the comparator which compares the potential detected by the capacitive divider with a reference voltage is an analog component which must, in order to present the required precision, include a complex arrangement of transistors.

These drawbacks are particularly felt in the case of a watch comprising a large number of manual control devices. This is the case, for example, of so-called "handwriting recognition" watches which can receive commands when the user's finger "writes" a sign, for example alphanumeric, such as a number on the glass of the watch. This must then be equipped with several dozen control devices, each having a capacitive sensor disposed on the surface of the glass in order to allow recognition of the instantaneous position of the finger on the external face of the glass. The consumption of each control device then represents an important factor in determining the life of the watch battery.

The object of the present invention is to provide a watch fitted with a manual control device which at least partially remedies these drawbacks.

• un capteur capacitif comprenant une première armature disposée sur la face intérieure du verre, et dont l'autre armature est formée sélectivement par le positionnement d'un doigt d'un utilisateur de ladite montre sur la face extérieure du verre, ce capteur capacitif étant ainsi destiné à former une première capacité, ladite montre présentant également une seconde capacité parasite entre ladite première armature et le boîtier, caractérisée en ce que ledit dispositif de commande manuelle comprend en outre
• un convertisseur tension-fréquence dont l'entrée est connectée à la jonction commune entre ladite première armature et ladite seconde capacité,
• un détecteur de fréquence branché entre ledit convertisseur et ledit circuit d'exploitation,

de manière que la fréquence d'oscillation dudit convertisseur varie en fonction de la présence ou de l'absence du doigt de l'utilisateur sur ladite face extérieure du verre.The subject of the present invention is therefore a watch comprising a case forming a mass, a glass and at least one manual control device which is connected to an operating circuit intended to perform a predetermined function of the watch under the action of said device. manual control, the latter comprising

• a capacitive sensor comprising a first armature disposed on the interior face of the glass, and the other armature of which is selectively formed by the positioning of a finger of a user of said watch on the exterior face of the glass, this capacitive sensor thus being intended to form a first capacity, said watch also having a second parasitic capacity between said first frame and the case, characterized in that said manual control device further comprises
• a voltage-frequency converter whose input is connected to the common junction between said first armature and said second capacitance,
• a frequency detector connected between said converter and said operating circuit,

so that the frequency of oscillation of said converter varies as a function of the presence or absence of the user's finger on said outer face of the glass.

Thus, to obtain a resolution of the manual control device comparable to that of the device of the aforementioned Swiss patent, it is possible to reduce the capacity of the capacitive sensor compared to that of the sensor used in this prior art. This has the consequence that the load to be placed on the capacitive sensor can be significantly lower, resulting in lower energy consumption each time the user wants to execute a command. This can extend the life of the watch battery.

In addition, by using the capacitive sensor and the parasitic capacitance of the watch as elements determining the frequency of the voltage-frequency converter, the present invention makes it possible to create a control signal whose detection of the logic states can be done by digital means of which the implementation is simpler than that of an analog circuit used in the prior art.

• la figure 1 représente schématiquement une vue en coupe de l'agencement d'un capteur capacitif dans une montre conforme à la présente invention;
• la figure 2 représente le schéma d'un mode préféré de réalisation d'un dispositif de commande manuelle destiné à être utilisé dans une montre conforme à la présente invention; et,
• la figure 3 est un graphique représentant en fonction de la capacité de leurs capteurs capacitifs la résolution atteinte par une montre selon la présente invention et par une montre de l'art antérieur.

Other characteristics and advantages of the invention will appear during the description which follows, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 schematically shows a sectional view of the arrangement of a capacitive sensor in a watch according to the present invention;
• FIG. 2 represents the diagram of a preferred embodiment of a manual control device intended to be used in a watch according to the present invention; and,
• Figure 3 is a graph representing as a function of the capacity of their capacitive sensors the resolution reached by a watch according to the present invention and by a watch of the prior art.

FIG. 1 represents a sectional view of a watch 1 comprising a housing 2 and a glass 3. An electronic circuit 4 is disposed in the housing 2. A conductive electrode 5, preferably transparent, is arranged on the inner face 6 of the watch glass 1. The electrode 5 is connected to the electronic circuit 4 by a conductor 7. A battery or other source of electrical energy 8 is also placed in the housing 2 and is connected to the positive pole of the electronic circuit 4 by a driver 9.

The electrode 5 forms one of the armatures of a capacitive sensor 20, the other armature 21 of this capacitive sensor 20 being formed by the finger 10 of the watch wearer 1 when, in order to carry out a predetermined command in the watch , it touches the outer face of the glass 3 at the location of the electrode 5. The finger 10 of the wearer is connected to the ground 11 of the electronic circuit, like the whole body of the wearer, by means of the housing 2 which is in contact with the wrist of the latter and which is connected to the negative poles of the electronic circuit 4 and of the battery 8.

FIG. 2 represents the diagram of a manual control device 22 used in watch 1 of FIG. 1 and which makes it possible to generate a control signal in response to the activation of the capacitive sensor 20. This device 22 is connected to a frequency detector DF and in turn connected to an operating circuit CE which makes it possible to execute, in a manner known per se, the function of the watch that the user wishes to control.

The control device 22 comprises a capacitive sensor 20 while a parasitic capacitance C _p is by construction present between the electrode 5 and the case 2 of the watch 1. This parasitic capacitance is represented in FIG. 2 by a capacitor 23. The capacitive sensor 20 and the capacitor 23 are connected in parallel between the ground 11 and the inverting input of an operational amplifier 24.

The manual control device 22 also includes resistors 25, 26 and 27 all connected in series between the output of the amplifier 24 and the ground 11. The non-inverting input of the amplifier 24 is connected to a junction between the resistors 26 and 27. In this configuration, the amplifier 24 and the resistors 25, 26 and 27 form a Schmidt flip-flop which provides at its output 28, that is to say at the junction between the resistors 25 and 26, a signal having, as a function of the relative values of the voltages present at the inputs inverting and non-inverting amplifier 24, either a high logic level or a low logic level. Two zener diodes 29 and 30 mounted head to tail are connected between the output 28 and the ground 11, in order to stabilize the voltages respectively defining these logic levels.

The manual control device 22 further comprises a resistors 31 connected between the output 28 and the inverting input of the amplifier 24. This resistor 31 forms, with the capacitive sensor 20 and the capacitor 23, of a pass filter low which integrates the tension at the exit of the rocker of Schmidt. The potential of the armatures of the capacitors 20 and 23 is applied to the inverting input of the amplifier 24. As a result, the manual control device 22 functions as a voltage-frequency converter, in other words a voltage-controlled oscillator.

In the embodiment illustrated in FIG. 2, the voltage-frequency converter has been designed in the form of an astable multivibrator, because it creates a periodic signal having two quasi-stable states while oscillating freely. However, it can also be designed in the form of any generator of periodic signal or in another form of voltage-controlled oscillator. The arrangement illustrated in Figure 2 is particularly advantageous due to its simplicity of construction and the fact that no high precision electronic component is required.

où R₃₁, R₂₆ et R₂₇ sont respectivement les valeurs des résistances 31, 26 et 27, et C_tot est la capacité totale entre l'entrée inverseuse de l'amplificateur 24 et la masse 11. On voit donc que la fréquence d'oscillation du signal de sortie du dispositif de commande manuelle 22 est proportionnelle à l'inverse de la capacité totale C_tot et qu'ainsi la capacité du capteur capacitif en combinaison avec la capacité parasite déterminent la valeur de la fréquence d'oscillation du dispositif de commande manuelle 22.The oscillation period T of the control device 22 is given by the relation $${\text{T = 2R₃₁C}}_{\text{early}}\text{ln (1 + (2R₂₆) / R₂₇)}$$

where R₃₁, R₂₆ and R₂₇ are respectively the values of the resistors 31, 26 and 27, and C _tot is the total capacitance between the inverting input of the amplifier 24 and the ground 11. We thus see that the oscillation frequency of the output of manual control device 22 is proportional to the inverse of the total capacity C _tot and thus the capacity of the capacitive sensor in combination with the parasitic capacity determine the value of the oscillation frequency of the manual control device 22.

Thus, the frequency of oscillation of the voltage-frequency converter varies depending on the presence or absence of the user's finger on the outside of the glass. If the finger 10 of the watch wearer 1 is not placed on the crystal 3, the armature 21 of the capacitive sensor 20 is therefore absent from the circuit shown in FIG. 2. The total capacity C _tot is in this case equivalent to the stray capacitance C _p between the electrode 5 and the ground 11. The frequency of oscillation of the output signal of the control device 22 is then proportional to the inverse of the stray capacitance C _p .

On the other hand, when the finger 10 is placed on the glass 3, the frame 21 is formed and, consequently, the capacitive sensor 21 effectively acts on the control device 22. Under these conditions, the total capacity C _tot is equivalent to the inverse of the sum of the capacities C _d and C _p . Thus, the oscillation frequency of the output signal from the control device 22 is proportional to the inverse of the sum of the capacities C _d and C _p .

Since the information desired in the output signal is contained in its frequency, instead of being in the absolute value of its amplitude, it suffices to use digital means designed in a simple way to draw it. These means can be implemented, for example, by a pulse counter which is started for a fixed period of operation. The frequency, and therefore the presence or absence of the finger on the outside of the watch glass, is directly represented by the number of pulses received during this fixed period. These means are not described in more detail because they are well known to those skilled in the art.

FIG. 3 is a graph which shows that the resolution and the power consumption of the present invention are better compared to those obtained in the prior art. On the horizontal axis of this graph is plotted the relationship C _p / C _d , that is to say the relationship between the parasitic capacitance established between the fixed electrode 5 of the capacitive sensor and the housing 2 and the capacitance C _d of the capacitive sensor 20. On the vertical axis, the relative resolution of the manual control device has been taken, in other words the relationship between the low logic state and the high logic state of its output signal.

The curve 40 represents, in the case described in patent CH 607 872 cited above, the relative difference V _pr / V _ab between the two voltage values detected by the comparator, respectively in the presence and in the absence of the finger of the user. The value of the capacity C _ref was taken as being equivalent to the value of the capacity C _d .

Curve 40 shows that there is a large difference between the levels of the analog voltages of the prior device, and that a high resolution is therefore reached, if the relationship C _p / C _d is comparatively small. But under these conditions, the capacitance C _d of the capacitive sensor must be significantly greater than the stray capacitance C _p , which will increase the consumption of the manual control device. Conversely, a relation C _p / C _d which is comparatively large decreases the resolution of the manual control device, but a lower energy consumption is obtained, since then the capacity C _d is smaller.

The curve 41 of FIG. 3 represents, in the case of the invention, the difference between the two frequency values F _pr and F _ab generated at the output 28 of the control device 22, respectively when the finger of a wearer of watch 1 is placed on glass 3 and is absent from this glass, always as a function of the ratio C _p / C _d .

It should be noted that, to establish a valid comparison of the curves 40 and 41, they have been plotted by putting in the numerator the smallest value of the ratio of the voltages respectively of the frequencies. However, it turns out that the greatest value of the tensions (as far as the case of the aforementioned Swiss patent is considered) is generated in the absence of the finger, as in the case of the invention.

By making a comparison between curves 40 and 41, it can be seen that a clear improvement in resolution is obtained in the embodiment of the present invention shown in FIG. 2 than in the case of the prior art. For example, in the case where the capacity C _d is equal in value to the capacity C _p , the resolution is 25% higher than that of the prior art.

Furthermore, to reach a resolution of 0.5 for example, in the case of the prior art, the capacitance C _{d must} be at least twice as large as the stray capacitance C _p , which represents a considerable increase in the energy consumption of the watch battery compared to what is obtained for the same resolution in the case of the invention.

It should be noted that several modifications and / or improvements can be made to the watch according to the invention without departing from the scope thereof. In particular, the invention also relates to handwriting recognition watches comprising a plurality of manual control devices of the type of FIG. 2 in order to follow the position of the finger on the glass of a wearer of the watch and, consequently , allow recognition of a number or letter written by the wearer on the glass. In this case, the frequency detectors DF of all the manual control devices can be connected to the operating circuit CE of the watch, while the electrodes 5 of their capacitive sensors form an appropriate pattern on the glass 3 of the latter. .

In another embodiment, the manual control device le can comprise several capacitive sensors of the type defined above, the common junctions between the first armature and the second capacitance of each of these capacitive sensors being all connected to the input d 'a multiplexer. In this case, the output of the multiplexer is connected to the input of the frequency detector of the control device.

In this way, only one voltage-frequency converter is needed which samples each capacitive sensor at a frequency determined by the operation of the multiplexer. Those skilled in the art will understand that the capacitance C _d of the capacitive sensor shown in FIG. 2 can vary according to the precise positioning of the user's finger on the watch glass. Thus, the frequency of the oscillator of the voltage-frequency converter can gradually change when a finger placed on the glass approaches or moves away from the first frame of the capacitive sensor. To allow the detection of the presence or absence of the finger in front of the capacitive sensor, it is possible to define a sensitivity threshold corresponding to a given frequency change. When the change in frequency of the voltage-frequency converter is greater than the sensitivity threshold, this change is detected by the operating circuit. This sensitivity threshold can be different for each capacitive sensor forming the manual control device, and the values of all these thresholds can be stored in a memory in the operating circuit.

On the other hand, in the case of a manual control device comprising several capacitive sensors, the positioning of a user's finger can be detected by analyzing the change in frequency caused by each capacitive sensor. Thus, the frequency change caused by the position of the finger on the watch glass will be more pronounced for a capacitive sensor located near the finger and will be less pronounced for capacitive sensors further away from the finger. By analyzing the frequency changes of all the capacitive sensors, the position of the finger can be determined.

Claims (5)

Watch (1) comprising a housing (2) forming a mass, a glass (3) and at least one manual control device (22), which is connected to an operating circuit (CE) intended to perform a predetermined function of the shows under the action of said manual control device (22), the latter comprising - a capacitive sensor (20) comprising a first frame (5) disposed on the inner face (6) of the glass (3), and the other frame of which is selectively formed by the positioning of a finger (10) of a user of said watch (1) on the outer face of the glass (3), this capacitive sensor (20) thus being intended to form a first capacity (C _d ), said watch (1) also having a second parasitic capacity (C _p ) between said first frame and the housing (2), characterized in that said manual control device (22) further comprises - a voltage-frequency converter (22) whose input is connected directly to the common junction between said first armature (5) and said second capacitance (C _p ), - a frequency detector (DF) connected between said converter (22) and said operating circuit (CE), so that said capacitive sensor (20) and said stray capacitance (Cp) determine the frequency of oscillation of said converter as a function of the presence or absence of the user's finger on said outer face of the glass. Watch according to claim 1, characterized in that said voltage-frequency converter (22) is produced in the form of an astable multivibrator. Watch according to claim 2, characterized in that said common junction is connected to the input an amplifier (24) forming part of said astable multivibrator. Watch according to any one of the preceding claims, characterized in that it comprises a plurality of manual control devices, the capacitive sensors of which together form a pattern on the watch glass to allow recognition of writing on the external face of said watch. glass, the frequency detectors (DF) of all the control devices being connected to said operating circuit (CE). Watch according to any one of claims 1 to 3, characterized in that it comprises a plurality of said capacitive sensors together forming a pattern on the watch glass to allow recognition of writing on the outer face of said glass, and in what it further comprises a multiplexer the output of which is connected to the input of said voltage-frequency converter, the common junctions between said first armature and said second capacitance of each of said capacitive sensors being all connected to the input of said multiplexer.

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