OPERATING DEVICE FOR AN APPLIANCE, HOUSEHOLD APPLIANCE AND METHOD FOR CONTROLLING THE APPLIANCE

Abstract

An operating device contains a sensor surface, a signal generator for providing a control signal with a predetermined frequency for the sensor surface, an evaluation device which is configured to provide a sensor signal which is dependent on the capacitance of the sensor surface, and a control facility. In this process, the control facility is configured to determine measuring noise on the evaluation device at different frequencies and to select the frequency of the control signal in order to determine the sensor signal as a function of the determined measuring noise.

Claims

1. An operating device, comprising: a sensor surface; a signal generator for providing a control signal with a predetermined frequency; an evaluation device configured to provide a sensor signal being dependent on a capacitance of said sensor surface; and a control facility configured to determine measuring noise on said evaluation device at different frequencies and to select a frequency of the control signal in order to determine the sensor signal in dependence on the measuring noise determined.

2. The operating device according to claim 1, wherein the measuring noise is determined based on the sensor signal.

3. The operating device according to claim 1, wherein said control facility is configured to interrupt a determination of the sensor signal when said sensor surface is excited with a primary frequency, in order to determine the measuring noise when said sensor surface is excited with a secondary frequency.

4. The operating device according to claim 3, wherein interruptions take place periodically.

5. The operating device according to claim 1, wherein said evaluation device determines the sensor signal on a basis of the control signal by means of a sigma delta method.

6. The operating device according to claim 1, further comprising a determination facility for determining a user touching said sensor surface on a basis of the sensor signal.

7. The operating device according to claim 6, further comprising a driver configured to control a consumer in dependence on a determined touch.

8. A household appliance, comprising: the operating device according to claim 1.

9. A method, which comprises the steps of: providing a control signal with a predetermined frequency on a sensor surface; providing a sensor signal dependent on a capacitance of the sensor surface; determining measuring noise by an evaluation device at different frequencies; and selecting a frequency of the control signal in order to determine the sensor signal in dependence on the measuring noise determined.

10. The method according to claim 9, wherein: a number of frequencies are predetermined; and a primary frequency for the control signal is used in order to determine the sensor signal.

11. The method according to claim 9, which further comprises first determining the measuring noise using a secondary frequency when the measuring noise using the primary frequency exceeds a predetermined threshold value.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0028] FIG. 1 is a block diagram of a household appliance according to the invention;

[0029] FIG. 2 is a flow chart of a method for controlling an appliance; and

[0030] FIG. 3 is a graph showing an exemplary sensor signal.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a household appliance 100 with an operating device 105. Purely by way of example, the household appliance 100 is shown as a cooker. The household appliance 100 contains one or more consumers 110, wherein in the present case a consumer 110 can correspond to a heating facility for a cooking pot.

[0032] The operating device 105 is configured to detect a touch by a user 115 and to control the consumer 110 as a function of the touch. A determination facility 120 can be provided in order to determine a touch and possibly to convert a control signal into a function delivered by means of the consumer 110.

[0033] The operating device 105 contains a sensor surface 125, a signal generator 130, an evaluation device 135 and a control facility 140. The signal generator 130 is designed to supply the sensor surface 125 with a control signal in a predetermined frequency. The evaluation device 135 is configured to provide a sensor signal indicating a capacitance of the sensor surface 125. The control facility 140 is configured to control the signal generator 130 in order to adjust a frequency of the control signal. Moreover, the control facility 140 can determine a measuring noise in the sensor signal of the evaluation device 135. The evaluation device 135 can be configured to compensate for an influence of the frequency of the control signal on the determined sensor signal.

[0034] A driver 145 is optionally provided in order to control the consumer 110 on the basis of a signal provided by the determination facility 120. In the case of an induction cooker, the driver 145 can comprise a control for an inductive coil 110. On a radiation cooktop, the driver 145 can comprise a phase-angle control. The driver 145 can also comprise a semiconductor-based flow-current valve (solid state relay) or a relay, for instance.

[0035] In a preferred embodiment, a modulation capacitor is charged by means of a current source. Charge from the modulation capacitor is then recharged in a capacitor formed with the sensor surface 125, then the capacitor is discharged again by means of short-circuiting. In this process the capacitance of the modulation capacitor is preferably at least one order of magnitude greater than that of the capacitor formed with the sensor surface 125. The charging of the capacitor from the modulation capacitor and the discharging is repeated periodically with a predetermined frequency, while a voltage of the modulation capacitor is monitored at the same time. How often the capacitor can be charged from the modulation capacitor until its voltage drops to below a predetermined threshold value is counted here. The determined number can be used as an indication of the capacitance of the capacitor and thus of a touch of the sensor surface 125 by the user 115. The current source, a counter and a controller for charging and discharging the capacitors can be included in a programmable microcontroller. In one embodiment, the modulation capacitor has approximately 5,000 times the capacitance of the capacitor to be determined, if there is no touch of the sensor surface 125 and the counter can count up to 2{circumflex over ( )}13 cycles. Other designs are likewise possible.

[0036] It is proposed that the control facility 140 controls the signal generator 130 so as to use a first frequency. At the same time, the control facility 140 can determine a measuring noise on the sensor signal of the evaluation device 135. Under predetermined conditions, for instance when the determined measuring noise exceeds a predetermined threshold value, the control facility 140 can control the signal generator 130 so as to provide the control signal with a second frequency. In the thus materializing sensor signal, the control facility 140 can again determine a measuring noise. The control facility 140 can then decide whether the measuring noise is smaller using the first or the second frequency. The determination of the capacitance of the sensor surface 125 can then be continued with the more advantageous frequency on the basis of the control signal.

[0037] FIG. 2 shows a flow chart of a method 200 for controlling an appliance, in particular the household appliance 100. The method 200 is shown in the form of a status transition system. In a first state 205, with which the method 200 can begin, a frequency f0 is assumed for the control signal of the signal generator 130 on the sensor surface 125. The sensor surface 125 is controlled with the control signal of the selected frequency and a noise or measuring noise of the sensor signal can be determined when the frequency f0 is used as the primary frequency. Moreover, a filter chain which is related to the secondary frequency f1 can be updated. To this end, a change can be made periodically to the secondary frequency f1.

[0038] Under one predetermined condition, for instance periodically or when it is determined that the determined measuring noise exceeds a predetermined threshold value s with respect to f0, in step 210 a measuring noise can be determined with respect to the other frequency f1. To this end, the sensor surface 125 can be excited by means of the signal generator 130 with a control signal of the frequency f1. A sensor signal produced in the process can be examined for noise. It is then possible to determine that the noise with respect to the initially used frequency is less than or greater than the noise with respect to the other frequency. If the first frequency brings about less noise, it is then possible to return to step 205. On the other hand, if the other frequency brings about less noise, it is possible to branch into step 215.

[0039] Step 215 corresponds to step 205, but the other frequency f1 as the primary frequency is selected as the frequency of the control signal of the sensor surface 125. With respect to this frequency, a measuring noise of the sensor signal of the evaluation device 135 is determined. A filter chain with respect to the first frequency f0 can be updated.

[0040] Under a further predetermined condition, for instance when the determined measuring noise with respect to the selected frequency f1 exceeds a predetermined threshold value, it is possible to branch into step 220. Step 220 corresponds to step 210 with the difference that a measuring noise is determined with respect to the frequency f0. To this end, the control signal with the frequency f0 can be applied to the sensor surface 125.

[0041] If a thus determined measuring noise with respect to the frequency f0 is less than the previously determined measuring noise with respect to the frequency f1, it is then possible to branch into step 205, where f0 is selected as the new primary frequency for the control signal on the sensor surface 125. On the other hand, the method 200 can move back to step 215, where the frequency f1 is selected for the control signal of the sensor surface 125.

[0042] FIG. 3 shows an exemplary sensor signal 305. Individual measurements of the sensor signal are marked in the horizontal direction. The sensor signals are plotted as values in the vertical direction. Scales of both axes are to be considered as exemplary.

[0043] Between time instants 1 and 20 the sensor signal is not influenced by an interference source.

[0044] The considered values differ from one another only minimally and a measuring noise can be correspondingly minimal.

[0045] An interference signal in the region of the sensor surface 125 is coupled between measured values 21 and 49. Consecutive measured values have significantly larger relative distances from one another. A determined measuring noise in this region is considerably greater than in the first region described above.

[0046] By selecting a control signal with a suitable frequency, the influence of the interference signal can be minimized. In the example shown, the first frequency f0 can correspond to the first region between the measured values 1 and 20, and the second frequency f1 to the region between the measured values 21 and 49. In both instances, it is not assumed that the sensor surface 125 is touched by a user 115. In the embodiment shown, it is preferred to continue to determine a touch on the basis of the first frequency f0.

[0047] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:

100 Household appliance
105 Operating device

110 Consumer

115 User

[0048] 120 Determination facility
125 Sensor surface, electrode
130 Signal generator
135 Evaluation device
140 Control facility

145 Driver

200 Method

[0049] 205 Control sensor surface with f=f0
Determine noise (N) at f0
210 Determine noise (N) at f1
215 Control sensor surface with f=f1
Determine noise (N) at f1
220 Determine noise (N) at f0
305 Sensor signal