WO2008107834A2

WO2008107834A2 - Changing modes in a device

Info

Publication number: WO2008107834A2
Application number: PCT/IB2008/050759
Authority: WO
Inventors: Willem F. Pasveer; Martin Ouwekerk; Ronald Dekker
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-03-06
Filing date: 2008-03-03
Publication date: 2008-09-12
Also published as: WO2008107834A3

Abstract

A method is provided of changing between modes in a device. The method comprises changing the mode of the device in response to a change in the temperature of a first point of the device relative to the temperature of a second point of the device. Such a change in temperature may be created, for example, by the body heat from a user picking the device up. In certain embodiments, this allows the device to be switched between a completely powered-down mode to a powered-on mode without consuming any power in the powered-down mode. Further, the method provides a convenient and user- friendly way of operating the device.

Description

Changing modes in a device

FIELD OF THE INVENTION

The present invention relates to a device adapted to change mode and a method for changing between modes in a device.

BACKGROUND OF THE INVENTION

Many devices in the modern world are operated by means of a switch. Electric lights, mobile phones, televisions etc, must all be powered on or off by means of a switch.

Efforts have been directed towards making these switches as user- friendly as possible. For example, US 2004/0119484 discloses a device which monitors the capacitance of an electrode with its surroundings. When a human hand is near the electrode, the capacitance increases, and this change can be detected and used as the signal to power up the device.

Many devices have a third power state, commonly referred to as a "standby mode". When a device is in the standby mode it uses less energy than it would when fully switched on. However, the device will still consume a considerable amount of power when in the standby mode. For example, the device of the above US patent application, US 2004/0119484, requires a voltage to be maintained across the electrode so that the capacitance can be monitored.

Accordingly, there is a need for a device that can switch from a first mode, for example a completely powered-down mode, to a second mode, for example a standby or fully operative mode, in a user- friendly manner.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a method of changing between modes in a device. The method comprises changing the mode of the device in response to a change in the temperature of a first point of the device relative to the temperature of a second point of the device.

This has the advantage that a device can change modes of operation based on a detected relative temperature change, thus providing a user- friendly method of operation. Furthermore, when changing form a power-down mode to a standby or fully operative mode, the invention has the advantage of not consuming power whilst in the power-down mode.

According to a second aspect of the present invention, there is provided a device adapted to change mode in response to a change in the temperature of a first point of the device relative to the temperature of a second point of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, wherein like reference numerals refer to like features, in which:

Fig. 1 is a flowchart of a method of changing modes in a device; and

Fig. 2 is a schematic circuit diagram of a device;

Fig. 3 is a schematic circuit diagram of an alternative device; and

Fig. 4 is a schematic diagram of a device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 is a flowchart of a method for changing between modes in a device.

In step 10, the device detects a change in the temperature of a first point in the device relative to the temperature of a second point in the device. If no change is detected, the process waits at step 10 until a change is detected. Thus the device is continuously attempting to detect a relative temperature change.

In this description, the term "relative temperature change" is used to describe the situation where the temperature at a first point in the device changes relative to the temperature of a second point in the device. For example, the two points may initially be at the same temperature, but then the temperature of the first point increases and the temperature of the second point remains the same, meaning the temperature of the first point has changed relative to the temperature of the second point. In another example, a constant temperature difference may initially exist between the two points; however, a heat source that is closer to the first point than the second point causes the temperature of the first point to rise more quickly than the temperature of the second point. Again, the temperature of the first point has changed relative to the temperature of the second point. Thus, the method may detect the presence of a temperature difference, or gradient, that previously did not exist, or detect a change in a pre-existing temperature gradient. It will be appreciated that the references above to the temperature of the first point increasing or rising may also include the temperature at the first point decreasing or falling.

If a relative temperature change is detected, in step 20 the device changes between modes. This may be, for example, changing between any one of a number of power modes. For example, the relative temperature change may be used to change from a completely powered-down mode to a powered-up mode; from a stand-by mode to a powered- up mode; or from a completely powered-down mode to a standby mode; and vice versa for each respective example.

It will be appreciated that the method may also be used to change between modes unrelated to the power state of the device. For example, a device could detect a relative temperature change and thereafter communicate with another device and cause that other device to change modes. In this way, a light switch may be configured to communicate with a light control unit to switch on the electric lights in a room, for example.

The present invention overcomes the problems of the prior art by detecting a relative temperature change and using the relative temperature change as a signal for causing the device to change mode. Such a relative temperature change may be produced, for example, by the proximity of a user's hand. In this case, the device may be configured to switch from a low-power mode to a high-power mode when a user picks up or holds the device. The device may further be configured to detect the relative temperature change when the user puts down or releases the device, and switch from the high-power mode back to the low-power or powered-down mode. This is, of course, very convenient for the user, who consequently does not need to spend time switching between modes in the device. This also has the advantage that the device can stay in a low-power mode when not actively in use, thereby conserving power. The invention may also be useful, for example, in devices that are expressly designed to detect and report fluctuations in temperature, for example in industry. Such devices could remain inactive until a relative temperature change is detected, at which point they would power on, report the data to some other location such as a mainframe computer, and then power down once the data has been reported. Further applications may be in physiological sensors, for example, used to monitor the health of a person wearing them. In a hospital, the sensors could be adapted to power on only when the sensors are attached to the body of the patient. Skiers could wear a device that sends a distress signal in the unfortunate event that they are caught and buried by an avalanche. In security applications, fingerprint sensors could be configured to power-on in response to a user applying a finger to the sensor, and thereafter power-off at some predetermined time later, or in response to the user's finger being removed. Such an arrangement has the advantage of only consuming power in response to the fingerprint sensor being swiped.

Figure 2 shows a schematic circuit diagram of a device 110 according to an exemplary embodiment of the present invention.

In the preferred embodiment the device 110 comprises a thermoelectric module 120, which itself comprises thermoelectric material 122 connected between two electrodes 124, 126. The thermoelectric material 122 generates a voltage in response to a temperature difference across it. This effect is well known in the art and is commonly referred to as the "Seebeck effect". Thus a temperature gradient across the thermoelectric material 122 will lead to a voltage between the two electrodes 124, 126. Advantageously, the electrodes 124, 126 may be placed on opposite sides of the device, or otherwise as far apart as possible, in order to maximize the temperature difference and therefore the voltage.

The thermoelectric module 120 is connected to a switch 128, for example a voltage operated switch such as a transistor, such that when a temperature difference is present, and the associated voltage generated, the switch 128 is closed. The switch 128 is shown as being connected between a processor 130 and a power source 132, and operates such that closing the switch 128 completes the circuit between the processor 130 and the power source 132, so that the processor 130 receives power from the power source 132. It will be appreciated that the switch 128 may be used to power the device in some other manner compared to that shown in Figure 2.

Of course, the device 110 may be small and therefore the distance between the electrodes 124, 126 correspondingly small. Further, it is desired that the device be responsive to relatively slight changes in temperature. Therefore, the temperature gradient may be small and exceedingly short-lived. A user's hand, for example, will rapidly establish a thermal equilibrium in a small device, and so a temperature gradient will exist only for a brief time when the device is first touched. To overcome these problems, a second switch 134 may be provided in parallel with the first switch 128, such that only one of the switches 128, 134 need be closed in order to complete the circuit between the processor 130 and the power source 132. The processor 130 controls the second switch 134. In operation, once the first switch 128 is closed owing to the voltage generated by the thermoelectric module 120 and power is supplied to the processor 130, the processor 130 closes the second switch 134. In this way, the circuit remains complete even when there is no temperature gradient in the thermoelectric module 120. In a simple device, this may complete the operation of the present invention, i.e. the device 110 has changed mode from an "off" mode to an "on" mode. However, in further embodiments, the processor 130 may be used to change the mode of another processor (not shown in Figure 2), for example, from "standby" mode to "on" mode, or to otherwise communicate with another device and change the mode of that other device. Furthermore, the processor 130 may be controlled to turn off the switch 134 at some predetermined time or in response to some predetermined event, thus enabling the device to become powered down after the initial temperature gradient has been detected. For example, when switch 128 is initially activated by a voltage from the thermoelectric module 120, the processor 130 could be configured to activate switch 134 as mentioned above, such that the switch 134 maintains the device in a powered-up state. Thereafter, once the processor has performed some specific task, such as gathering data and transmitting the data to a remote location, the processor may be configured to turn off the switch 134, thereby causing the device 110 to revert to the power down mode once more. The device remains in the power down mode until a subsequent temperature gradient causes a voltage to be generated, which in turn causes the switch 128 to be activated, and so on.

The configuration of Figure 2 has many advantages. No power is required by the device 110 to detect a temperature gradient-the voltage is generated within the thermoelectric module 120 by means of a well-known natural physical effect. Therefore the device 110 may be completely powered down and yet still be responsive to temperature gradients, saving power that would otherwise be wasted by remaining in a standby mode. Further, the configuration has the afore-mentioned advantage that it is very easy and convenient to use.

Figure 3 shows an alternative schematic circuit diagram in accordance with the present invention. The device 140 comprises a thermoelectric module 120, which itself comprises thermoelectric material 122 connected between two electrodes 124, 126. The thermoelectric material 122 generates a voltage in response to a temperature difference across it. Thus a difference between the temperature of the first electrode 124 and the temperature of the second electrode 126 will lead to a voltage between the two electrodes 124, 126. The thermoelectric module 120 is connected to a switch 128, for example a voltage operated switch such as a transistor, such that when a temperature gradient is present, and the associated voltage is generated, the switch 128 is closed. The switch 128 is shown as being connected between a processor 142 and a power source 132, and operates such that closing the switch 128 completes the circuit between the processor 142 and the power source 132, so that the processor 142 receives power from the power source 132, as described with reference to Figure 2.

A second switch 134 is provided in parallel with the first switch 128. The processor 142 controls the second switch 134. However, the device 140 of Figure 3 differs from the device 110 of Figure 2 in that the switch 134 connects the power source 132 to a different input of the processor 142 than the switch 128.

In operation, the device 140 operates in a similar way to the device 110 when powering on. A voltage generated by thermoelectric module 120 will cause the switch 128 to close, thus connecting the processor 142 with the power source 132. The processor 142 then operates to close the second switch 134, thereby creating a robust electrical connection between the processor 142 and the power source 132 — when a temperature difference no longer exists between the electrodes 124, 126 and the switch 128 is open, the processor 142 is still connected to the power source 132.

However, as the switch 128 connects to a different input of the processor 142, the processor 142 will be able to detect further voltage pulses generated by the thermoelectric module 120, even when it is connected to the power source 132. Thus, in this embodiment, the processor 142 will be able to detect further temperature differences, for example caused by a user putting the device 140 down. The processor 142 may then use this information to change the device 140 to a mode which consumes less power. For example, the processor 142 may operate to open switch 134, thereby powering down the device 140, or placing the device in a standby mode.

There are many alternative methods of detecting differences in temperature that will be apparent to one skilled in the art, and that are within the scope of the present invention. For example, at a basic level, two temperature sensors could be used to measure the temperature at two points. When a temperature difference is detected between the two temperature sensors (i.e. a temperature gradient is found), the mode of the device is changed. Although this embodiment may in practice require some power to operate, and therefore be unable to change from a truly off mode to an on mode, it would still have the benefit of being exceptionally easy to operate and convenient for the user. Embodiments of the invention which detect a temperature difference caused by the body heat of a user may have difficulty operating in warm environments where the atmospheric temperature is similar to body temperature. In the embodiments described with reference to Figures 2 and 3, for example, the body heat of the user may not significantly alter the temperature at one of the electrodes 124, 126 if the atmospheric temperature is above 30°C, and therefore no voltage would be generated by the thermoelectric module 120. One method of overcoming this difficulty would be to provide a temperature sensor within the device which detects when the atmospheric temperature is too high. The temperature sensor could then operate an output to inform the user that the device may not work reliably; for example, by switching on a warning LED. Another alternative may be to provide a temperature-sensitive substance on the exterior of the device. Such substances are well known to those skilled in the art, and may be color coordinated such that they change to a different color when the temperature reaches a point at which the device may not operate reliably. However, such a solution does not solve the problem of a high atmospheric temperature itself. This problem may be overcome by operating the thermoelectric module described earlier in reverse. That is, by applying a potential difference between the two ends of a thermoelectric material, a temperature difference can be generated between those two ends: one end will get hotter, and the other end will cool down. This effect is known as the "Peltier effect", and is the reverse of the Seebeck effect described earlier. At some point, an equilibrium position is reached and the temperatures of the two ends will not change, maintaining a constant temperature difference.

Thus, in this embodiment, the electrode at one end of the thermoelectric module will be "cold" and the electrode at the other end of the thermoelectric module will be "hot".

Of course, one skilled in the art may be able to think of alternative methods of artificially creating a temperature difference between the two electrodes, without departing from the scope of the invention. For example, in an alternative embodiment, conventional refrigeration methods may be used to cool one of the electrodes. In operation, when a user picks up the device, or otherwise comes near enough to the device to cause a change in temperature, the body heat of the user will serve to warm up the cold electrode, or to cool down the hot electrode. This action will reduce the temperature difference between the two electrodes, and therefore reduce the potential difference between those two electrodes. The change in potential difference can be detected and knowledge thereof can be used to change the mode of the device as indicated before.

Preferably, this embodiment may be used only when the atmospheric temperature reaches a certain threshold (for example 30°C) above which the device will not operate normally. Thus the temperature sensor described above may also be used to switch the device between the normal "Seebeck" embodiment and the Peltier embodiment when the atmospheric temperature reaches that threshold. In this way, the device can obtain the benefits of operation at all temperatures (Peltier embodiment) and minimal power consumption (Seebeck embodiment). However, the Peltier embodiment is equally applicable at all temperatures and therefore can be used in isolation from the Seebeck embodiment described earlier.

Figure 4 shows a schematic diagram of a device 200 according to an embodiment of the present invention.

The device 200 comprises a first part 210 which contains a first electrode, together with further electronics for operating the device 200.

The device 200 further comprises a second part 220 separate from the first part 210, with a thermoelectric module 230 separating the first and second parts. The second part 220 contains a second electrode, with the thermoelectric module 230 being electrically connected between the first and second electrodes. The first and second parts are further connected to each other by an electrical connection 250.

The second part 220 further comprises a temperature-dependent, color- coordinated substance 240, which is adapted to change color when the temperature of the second part exceeds a predetermined threshold.

The further electronics in the first part 210 comprise electronics for applying a potential difference between the first and second electrodes, and therefore across the thermoelectric module. The further electronics further comprise electronics for detecting the voltage between the first electrode and the second electrode.

In operation, a potential difference is applied across the thermoelectric module, which generates a temperature difference ΔT between the first and second electrodes. Thus the first part heats up, and the second part cools down. An equilibrium position is achieved and the temperatures of both electrodes do not change further. In a preferred embodiment, a temperature sensor may indicate when the second part 220 has reached this steady temperature, thereby indicating to a user that the device is ready for use. Thus a user who applies, for example, a finger to the cold second part 220 will raise the temperature of the second part 220. This in turn will reduce the temperature difference between the two electrodes, and therefore the potential difference between those electrodes. This change in voltage can be detected by the electronics in the first part 210, and the mode of the device 200 changed. For example, the device 200 may switch from a standby mode to a fully operational mode.

The invention described in the embodiments above has the advantage of enabling the mode of a device to be changed in an easy and convenient manner. Furthermore, in certain embodiments the device can change from a completely powered-down mode to a powered-up mode without consuming any power in the powered-down mode.

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. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim, "a" or "an" does not exclude a plurality, and a single processor or other unit may fulfill the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

CLAIMS:

1. A method of changing between modes in a device, the method comprising: changing the mode of the device in response to a change in the temperature of a first point of the device relative to the temperature of a second point of the device.

2. A method as claimed in claim 1, wherein the device comprises a thermoelectric module electrically connected between the first point and the second point.

3. A method as claimed in claim 2, wherein the temperature of the first point is initially the same as the temperature of the second point, and further comprising detecting a voltage generated in the thermoelectric module in response to the temperature of the first point changing relative to the temperature of the second point.

4. A method as claimed in claim 3, further comprising using said voltage to establish an electrical connection between an electrical circuit and a power source.

5. A method as claimed in claim 4, further comprising establishing a second electrical connection between the electrical circuit and the power source.

6. A method as claimed in claim 1, further comprising: first establishing a difference between the temperature of the first point and the temperature of the second point.

7. A method as claimed in claim 6, wherein the device comprises a thermoelectric module electrically connected between the first point and the second point, said difference between the temperature of the first point and the temperature of the second point being established by applying a potential difference between the first point and the second point.

8. A method as claimed in claim 7, further comprising detecting a change in the potential difference between the first point and the second point, caused by a change in temperature of the first point relative to the temperature of the second point.

9. A method as claimed in claim 1 , further comprising changing the mode of a second device in response to a change in the temperature of the first point relative to the temperature of the second point.

10. A device adapted to change mode in response to a change in the temperature of a first point of the device relative to the temperature of a second point of the device.

11. A device as claimed in claim 10, comprising a thermoelectric module electrically connected between the first point and the second point.

12. A device as claimed in claim 11, wherein the temperature of the first point is initially the same as the temperature of the second point, and the device is adapted to detect a voltage generated in the thermoelectric module in response to the temperature of the first point changing relative to the temperature of the second point.

13. A device as claimed in claim 12, further comprising: an electrical circuit; a power source; and a first switch electrically connected between the electrical circuit and the power source, wherein the first switch is adapted to close in response to said detected voltage, thereby establishing an electrical connection between the electrical circuit and the power source.

14. A device as claimed in claim 13, further comprising: a second switch electrically connected between the electrical circuit and the power source, in parallel with the first switch; wherein the electrical circuit is adapted to close the second switch after the first switch is closed.

15. A device as claimed in claim 10, further comprising: a mechanism for establishing a difference between the temperature of the first point and the temperature of the second point.

16. A device as claimed in claim 15, wherein the establishing mechanism comprises: a thermoelectric module electrically connected between the first point and the second point; and means for applying a potential difference between the first and the second point.

17. A device as claimed in claim 16, further comprising: means for detecting a change in the potential difference between the first point and the second point.

18. A device as claimed in claim 10, wherein the first point and the second point are positioned on opposite sides of the device.