FIELD OF THE INVENTION

This invention relates to an electronic device comprising an external housing and means for detecting when the external housing is being tapped on by a user. BACKGROUND OF THE INVENTION

Such an electronic device is disclosed in the international patent application published as WO 2012/020356 Al . Said application discloses a tap-sensitive alarm clock. The alarm clock has an external housing and a vibration sensor mechanically coupled to the external housing. When the vibration sensor receives a shock as a result of a user tapping on the external housing, a control circuit coupled to the vibration sensor controls a function of the alarm clock. For example, when the alarm sounds, tapping the external housing may interrupt the noise being produced by the alarm clock. The use of tap detection for controlling the alarm clock is preferably used for controlling the snooze function of the alarm clock. For a person who has just woken up, it is much easier to just tap the external housing of the device at an arbitrary position than to find and press a snooze button provided at a specific position on the external housing of the device.

In the prior art device, the vibration sensor used for this tap detection is a piezo element attached to the external housing of the device. Tapping the external housing causes deformation of the external housing, which causes deformation of the piezo element. The piezo element converts the deformation into a voltage signal. Electrical wiring couples the vibration sensor to a control circuit of the alarm clock where the voltage signal is amplified, filtered and used for controlling functions of the alarm clock, e.g. the snooze function.

However, the vibration sensor of WO 2012/020356 Al has a number of technical disadvantages. Connecting the piezo element to the external housing and soldering the wiring between the piezo element and the control circuit are manual operations and thus costly. Connection tolerances between the piezo element and the external housing strongly affect the voltage signal of the piezo element, which makes it difficult to reliably set trigger levels without calibrating individual devices. OBJECT OF THE INVENTION

It is an object of the invention to provide an electronic device with a more reliable tap detection mechanism.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, this object is achieved by providing an electronic device comprising a printed circuit board with electronics for controlling main functions of the electronic device, an external housing enclosing the printed circuit board and internal parts of the electronic device, a proximity sensor mounted on the printed circuit board and arranged for providing a signal depending on variations of a proximity of a predetermined local part of the external housing to the printed circuit board, and a control circuit coupled to the proximity sensor and arranged to detect, based on the signal, when the external housing is being tapped on by a user.

The piezo element of the alarm clock of WO 2012/020356 Al makes use of the small deformations of the external housing and the piezo element when the external housing is being tapped on by the user. However, by tapping the external housing, the external housing is not only deformed but also displaced, at least locally. Although the displacement may be very small and hardly visible to the human eye, the signal provided by the proximity sensor is capable of detecting the displacement. As will be elucidated below, different types of proximity sensors are suitable for use in the electronic device according to the invention.

Like the piezo element of the prior art, the proximity sensor provides an electronic signal indicating when the external housing is being tapped on by the user. The electronic signal is then processed by the control circuit of the electronic device. In contrast to the piezo element used in the prior art, the proximity sensor does not need a soldered connection to the control circuit. The proximity sensor is, at least partly, mounted on the printed circuit board itself and therefore needs no soldered connections to other electronic units. The control circuit may be provided on the same printed circuit board as the proximity sensor.

In those embodiments where the proximity sensor needs to cooperate with an additional element attached to the predetermined local part of the external housing, this additional element does not need to be connected to further electronics. The proximity sensor itself, which provides the signal indicating the proximity of the predetermined local part of the external housing to the printed circuit board, is already mounted on the circuit board. In addition, even for the embodiments with some additional element attached to the external housing, connection tolerances of this additional element are not important. Connection tolerances may influence the absolute value of the signal generated by the proximity sensor, but tapping of the external housing by users of the device is detected by monitoring variations of the signal of the proximity sensor rather than the absolute value of the signal.

The proximity sensor may e.g. comprise a light emitter and a photodetector mounted on the printed circuit board in such a way that, in use, light emitted by the light emitter is reflected towards the photodetector via an inner surface of the predetermined local part of the external housing. Due to divergence of the emitted light, the signal provided by the photodetector depends on the distance between the proximity sensor and said inner surface via which the light is reflected, i.e. the inner surface of the predetermined local part of the external housing. A reflective material may be provided at the inner surface of the predetermined local part of the external housing for improving its reflective properties and the reliability of the proximity sensor. When tapping causes the external housing and the predetermined local part thereof to move or vibrate relative to the printed circuit board and the proximity sensor mounted thereon, the signal generated by the photodetector changes accordingly and the control circuit detects the tapping.

In another embodiment, the proximity sensor comprises a capacitive sensor with a first electrode and a second electrode mounted on the printed circuit board and arranged in such a way that a capacitive coupling between the first electrode and the second electrode depends on the proximity of the predetermined local part of the external housing to the printed circuit board. Also this capacitive sensor does not require any wired connection between elements mounted at the external housing and elements on the printed circuit board. To improve the sensitivity to variations of the distance between the external housing and the printed circuit board, the capacitive sensor may cooperate with a further electrode provided at the predetermined local part of the external housing, the further electrode being arranged in such a way that a capacitive coupling between the first electrode and the second electrode depends on a proximity of the further electrode to the printed circuit board.

The same holds for yet another embodiment, wherein the proximity sensor comprises an inductive sensor with an inductive coil wound around a ferromagnetic core mounted on the printed circuit board, wherein the inductive sensor cooperates with an electrode provided at the predetermined local part of the external housing in such a way that an inductive coupling between the electrode and the inductive coil depends on a proximity of the electrode to the printed circuit board.

An advantage of the capacitive and the inductive proximity sensors compared to the light-based proximity sensor may be that the operation of the capacitive and the inductive proximity sensors is not influenced by external lighting conditions.

Optionally, the predetermined local part of the external housing is provided on an upper portion of the external housing, wherein the upper portion is connected to a lower portion of the external housing by means of a resilient member. The upper portion of the external housing constitutes the most probable portion of the external housing where the user will tap the external housing as a result of a natural reflex action. The resilient member increases the displacements of the predetermined local part of the external housing relative to the printed circuit board when the external housing is tapped on by the user by such a natural reflex action. The resilient member may e.g. comprise a rubber element for providing some additional freedom of movement of the upper portion of the external housing relative to the printed circuit board. This may increase the sensitivity of the proximity sensor. It is however noted that the invention also comprises embodiments wherein the predetermined local part of the external housing, that cooperates with the proximity sensor, is integrally formed with the external housing or part of the external housing enclosing the printed circuit board.

The electronic device may further comprise a clock and an alarm, both coupled to the control circuit, wherein the control circuit is operative to activate the alarm at a predefined time, e.g. set by the user, and to de-activate the alarm when the proximity sensor detects that the external housing is being tapped on by a user. The tap detection according to the invention is e.g. useful in combination with a so-called snooze function in a wake-up light or other alarm clock, wherein the alarm can be temporarily de-activated by the user after being woken-up by the alarm.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 schematically shows an alarm clock with a tap detection unit according to the invention,

Figure 2 schematically shows a close up of an embodiment of the tap detection unit of the alarm clock in figure 1, Figure 3 schematically shows a tap detection unit with a capacitive proximity sensor according to the invention, and

Figure 4 schematically shows a tap detection unit with an inductive proximity sensor according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 schematically shows an alarm clock 10 with a tap detection unit according to the invention. In the following, the invention will be elucidated by describing this alarm clock 10 and how tapping its external housing 11 triggers snoozing or turning off the alarm. It is however to be noted that the tap detection may also trigger different functions or may be used in different types of electronic devices comprising an external housing, such as radios, televisions, DVD players or gaming consoles. A close up of an embodiment of the tap detection unit is provided in figure 2. The alarm clock 10 comprises an external housing 11 enclosing all or most of the internal parts of the alarm clock 10 including a printed circuit board 12. The external housing 11 is typically made of a metal or a plastics material or a combination thereof, but also other materials may be used. The external housing 11 encloses the printed circuit board 12, which has a control circuit 26. The external housing 11 further comprises a clock with a display 13 for indicating a current time. The display 13 may also be used for, e.g., indicating whether the alarm is set, at what time the alarm is set or for providing any other information that might be relevant for the operation of the alarm clock 10. When the alarm goes off, an alarm sound may be emitted by a speaker 14. Buttons 15 or other user input means are provided for enabling the user to set the appropriate alarm time and control the functions of the alarm clock 10.

The control circuit 26 is operative to perform part of the functions of the alarm clock 10. Additional control circuits may be provided for different aspects or functions of the alarm clock 10. For example, the tap detection, the clock, the display 13 and the speaker 14 may have their own interconnected control circuits, which may or may not be part of the same printed circuit board 12. Alternatively, all functions may be performed by only one control circuit 26.

In the embodiment of Figure 1, the control circuit 26 is at least operative to deactivate the alarm when the external housing 11 is being tapped on by a user. When the external housing 11 is being tapped on, a distance between a predetermined local part of the external housing 11 and the printed circuit board 12 varies as a result of the vibrations of the external housing 11 caused by the tapping action. These variations of said distance are detected by the tap detection unit. In the embodiment of Figure 1, the predetermined local part of the external housing 11 is provided on an upper portion of the external housing 11 , and said upper portion is connected to a lower portion of the external housing 11 by means of a resilient member 16. The upper portion of the external housing 11 constitutes the most probable location of the external housing 11 where the user will tap the external housing 11 as a result of a natural reflex action. The resilient member 16 increases the displacements of the predetermined local part of the external housing 11 relative to the printed circuit board 12 when the external housing 11 is being tapped on by the user by such a natural reflex action. The resilient member 16 may e.g. comprise a resilient material like rubber, and it provides some additional freedom of movement of the upper portion of the external housing 11 relative to the printed circuit board 12. In the embodiment of Figure 1, the resilient member 16 is provided in a side wall of the external housing 11.

In a preferred embodiment, the alarm clock 10 is a wake-up light which in addition to or instead of the alarm sound uses light to wake up the user at the appropriate time. Wake-up lights are designed for providing a semi-natural wake up experience by gradually increasing a light intensity for simulating a natural sun rise. The increasing light intensity may be accompanied by wake up sounds from the speaker 14.

Figure 2 schematically shows a close up of an embodiment of the tap detection unit of the alarm clock 10 shown in figure 1. The tap detection unit comprises a light emitter 22 and a photodetector 23 mounted on the printed circuit board 12. In this embodiment, the light emitter 22 and the photodetector 23 are combined in one unit. The combined unit constitutes an optical proximity sensor 21 for detecting a proximity of a predetermined local part of the external housing 11 relative to the printed circuit board 12. In this embodiment, said predetermined local part of the external housing 11 is constituted by a location on the external housing 11 where light from the light emitter 22 is reflected towards the

photodetector 23 via an inner surface of the external housing 11 for detection by the photodetector 23. Such an optical proximity sensor typically uses infrared light, but also light of different wavelength ranges may be used. The photodetector 23 is shielded from the light emitting diode 22 such that no (or at least not too much) direct light from the light emitter 22 is detected by the photodetector 23. The closer the optical proximity sensor 21 is arranged to the external housing 11, the more light the photo detector 23 detects. In this way,

deformations and displacements of the predetermined local part of the external housing 11 relative to the printed circuit board 12 and the optical proximity sensor 21 are detectable from the signal generated by the photodetector 23. Because tapping the external housing 11 causes such deformations and/or displacements, the optical proximity sensor 21 can be used for tap detection. Optionally, a reflective material 24 is attached to the inside of the external housing 11 , at least on said predetermined local part thereof opposite to the optical proximity sensor 21 , in order to improve the sensitivity of the optical proximity sensor 21. The reflective material 24 may, e.g., be a metal foil.

In order to detect when the housing is being tapped on, the signal generated by the proximity sensor 21 is used to determine variations of the distance between the predetermined local part of the external housing 11 and the printed circuit board 12. By observing variations in the signal instead of the absolute value of the signal, the sensitivity and/or the accuracy of detecting the tapping of the external housing 11 by users of the device is improved. In addition, the influence of manufacturing tolerances on this sensitivity and/or accuracy is reduced.

Figure 3 schematically shows a tap detection unit with a capacitive proximity sensor 31. The capacitive proximity sensor 31 comprises a first electrode 32 and a second electrode 33 mounted on the printed circuit board 12. A capacitive coupling between the two electrodes 32, 33 depends on a proximity of a predetermined local part of the external housing 11, situated vertically above the electrodes 32, 33 in Figure 3, relative to the printed circuit board 12. Deformations and/or displacements of the predetermined local part of the external housing 11 relative to the printed circuit board 12 and the capacitive proximity sensor 31 are detectable from the signal generated by the capacitive detector 31. Because tapping the external housing 11 causes such deformations and/or displacements, the capacitive proximity sensor 31 can be used for tap detection. The sensitivity and accuracy of the capacitive proximity sensor 31 is improved by attaching an additional electrode 34 to the inside of the external housing 11 at the location of said predetermined local part thereof, i.e. opposite to the first and second electrodes 32, 33.

Figure 4 schematically shows a tap detection unit with an inductive proximity sensor 41. The inductive proximity sensor 41 comprises an inductive coil 42 wound around a ferromagnetic core 43. In this embodiment, the ferromagnetic core 43 is provided on the printed circuit board 12 and the inductive coil 42 is wound around the ferromagnetic core 43 and the printed circuit board 12. Alternatively, the ferromagnetic core 42 and the inductive coil 42 may be both provided on top of or below the printed circuit board 12, or

ferromagnetic cores 43 may be provided at both sides or only at the bottom side of the printed circuit board 12. An electrode 44 is provided at a predetermined local part of the external housing 11 opposite to the proximity sensor 41, i.e. situated vertically above the proximity sensor 41 in Figure 4. An inductive coupling between the electrode 44 and the inductive proximity sensor 41 depends on the proximity of the electrode 44 to the printed circuit board 12 and the inductive sensor 41. Deformations and displacements of the predetermined local part of the external housing 11 relative to the printed circuit board 12 and the inductive proximity sensor 41 are thus detectable from a signal generated by the inductive sensor 41. Because tapping the external housing 11 causes such deformations and/or displacements, the inductive proximity sensor 41 can be used for tap detection.

Alternative arrangements for providing an inductive proximity sensor may also be used. Instead of only one inductive coil 42 on the printed circuit board 12, the inductive proximity sensor may measure an inductive coupling between an inductive coil provided on the external housing 11 and one provided on the printed circuit board 12.

It is to be noted that the optical, capacitive and inductive sensors 21, 31, 41 of figures 2, 3 and 4 are only provided as examples of proximity sensors 21, 31, 41 that may be used for realizing the invention. Other known types of proximity sensors, not necessarily optical, capacitive or inductive ones, may be used with equal or similar success.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.