US 20050078027 A1
An apparatus for controlling functions of an appliance is described having a touch-sensitive control panel resistant to accidental activation. The touch-sensitive panel has a plurality of proximity sensor areas which may be selected by a user wishing to activate associated functions of the appliance. Driver circuitry coupled to the sensor areas is operable to output detection signals to a controller in response to a user selecting ones of the sensor areas. The controller is configured to activate functions of the appliance in response to these detection signals. For one or more functions of the appliance, for example a switching on function, the controller is configured to only activate the function when a user makes a pre-determined combination of at least two selections from the plurality of sensor areas. This reduces the chances of potentially dangerous functions being activated inadvertently and can further help a designer to provide an intuitive and uncluttered appearance to the control panel.
1. An apparatus for controlling functions of an appliance comprising:
a touch-sensitive control panel having a plurality of proximity sensor areas;
driver circuitry operable to output detection signals in response to selection of the proximity sensor areas; and
a controller operable to receive said detection signals from the driver circuitry and activate different functions of the appliance in response thereto, wherein the controller is operable to activate at least one function of the appliance in response to receipt of a pre-determined combination of at least two of said detection signals.
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The invention relates to touch-sensitive control panels, also known as touch screens, for controlling appliances.
Touch-sensitive control panels are becoming more common in domestic appliances. In addition to providing more aesthetically pleasing control interfaces, touch-sensitive control panels provide more flexibility than more conventional control panels based on mechanical switches and rotary knobs. Touch-sensitive control panels are also less prone to failure through use due to their lack of moving parts. Touch-sensitive control panels can allow for a sealed interface between a user and the inside of a domestic appliance. This prevents spilt fluid or other debris from entering a domestic appliance through the gaps which surround conventional mechanical switches and knobs. A touch-sensitive control panel additionally provides a surface which can easily be wiped clean. This makes them more hygienic that more conventional control panels as there are no crevices or joints in which dirt may accumulate.
However, a problem with touch-sensitive screens in that they can be prone to accidental activation. A conventional electric hob control might include a rotary dial which is ‘clicked-on’ from an off position to activate the hob. The rotary dial may then be further rotated to select a desired temperature for the hob. This kind of control require a specific rotary action to operate. In addition, the mechanical resistance of the control, for example the force required for it to be ‘clicked-on’, can be chosen to reduce the chance of accidental activation. This means it is unlikely that a child or a pet, for example, could activate the hob control unintentionally. A hob having a touch-sensitive control panel can more easily be activated by a child playing with the hob or a pet walking over the control panel. This can make such hobs, and other appliances having touch-sensitive control panels, potentially significant sources of danger. Furthermore, when a hob, or other appliance, with a touch-sensitive control panel is in normal use it can be relatively easy to accidentally change the appliance settings, for example the temperature of a hob, merely by brushing past the control panel when reaching across the appliance or when attempting to adjust some other function of the hob. This is undesirable since it prevents the appliance from functioning as the user intends, and how he believes it to be, operating.
According to a first aspect of the invention, there is provided an apparatus for controlling functions of an appliance comprising: a touch-sensitive control panel having a plurality of proximity sensor areas; driver circuitry operable to output detection signals in response to selection of the proximity sensor areas; and a controller operable to receive said detection signals from the driver circuitry and activate different functions of the appliance in response thereto, wherein the controller is operable to activate at least one function of the appliance in response to receipt of a pre-determined combination of at least two of said detection signals.
By allowing certain functions of the appliance to be activated only in response to a pre-determined combination of at least two selections from the plurality of proximity sensor areas, the chance of accidentally activating these functions is reduced. This provides for a domestic appliance which benefits from the advantages of a touch-sensitive control panel but does not suffer the drawback of being prone to inadvertent activation. This provides for a safer appliance. The complexity of the pre-determined combination may be selected according to the level of protection against inadvertent activation required. In addition, an elegant and uncluttered control panel can be designed whereby a number different functions are associated with a relatively small number of common sensor areas, the functions being activated according to different pre-determined combinations.
The pre-determined combination may correspond to a user selecting at least two different proximity sensor areas or to a user selecting a single proximity sensor area at different times. To further reduce the chances of inadvertent activation, the pre-determined combination of at least two selections may need to be made within a specified time period. For example, the combination of selections may need to be made within a time period less than 5, 4, 3, 2, 1, 0.5 or 0.1 seconds. Similarly, selections made within the combination may need to separated by a minimum time such that the specified time within which they are made is more than 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2 or 5 seconds, in order to activate the function with which they are associated.
In some embodiments of the invention, a function of the appliance activated in response to a user making the pre-determined combination of at least two selections may be subsequently cancelled by the user making only one of the selections comprising the pre-determined combination. For example, a user may be required to select both of two separate proximity sensor areas within a one-second time period in order to switch on an appliance from a stand-by mode. If these two sensor areas are closely spaced, the user can switch on the appliance with a simple sliding motion of his finger from one sensor area to the other. To avoid the need for separate sensor areas for switching the appliance off, the sensor areas associated with switching on the appliance can also be used to switch the appliance off. If desired this can require a similar combination of selections as are required to switch the appliance on. However, in general it is less dangerous to have an appliance accidentally switched off. For safety reasons, switch off should also be an easy operation to perform. It may thus be considered preferable to allow the user to switch off the appliance by selecting any one of the two sensor areas used to switch on the appliance without requiring any pre-determined combination of selections to be made.
In many appliances the use of a position sensitive proximity sensor area for which the driver circuitry is operable to output a detection signal dependent on the position of a touch within said position sensitive proximity sensor can assist operation of the appliance. For example a variable operating parameter of the appliance, such as temperature of a hob or speed of a food blender or washing machine drum, can be varied according a position detected by the position sensitive proximity sensor area. This provides a rapid and intuitive way for a user to set a variable parameter. In order to configure the position sensitive proximity sensor area to vary the variable operating parameter of the appliance, a user may be required to make a pre-determined combination of at least two selections from the plurality of proximity sensor areas, one of which being a selection of the position sensitive proximity sensor. This can help to provide against inadvertent adjustment of the variable parameter. In addition by allowing different variable operating parameters of the appliance, e.g. the temperatures of different heating elements in an oven, to be adjusted with the same position sensitive proximity sensor depending on other selected sensor areas, a number of different variable parameters may be adjusted by a control panel having only one position sensitive proximity sensor area. Position sensitive proximity sensor areas are generally relative complex and extend over a larger area than more basic binary detectors. Accordingly, a simple and uncluttered control panel can be provided.
Depending on how a designer wishes a control panel to appear, linear or rotary position sensitive proximity sensor areas may be used. For example where a variable operating parameter of an appliance is adjusted using a position sensitive proximity sensor, this can be a rotary position sensitive proximity sensor area disposed around a central proximity sensor areas. The central and rotary position proximity sensor areas may both need to be selected during adjustment of the variable operating parameter of the appliance. This provides for a neat and intuitive control panel layout.
A portion of an upper surface overlaying at least one of the proximity sensor areas may be recessed to assist a user's finger to be positioned during selection, for example, when selecting or adjusting a rotary proximity sensor area.
For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example to the accompanying drawings in which:
The driver circuitry 52 shown in
In step A, switching elements S2 and S3 are closed to clear any electric charge on the sampling capacitance Cs and the capacitance Cx provided by the sensor area 50. This is known as a “reset all” step. In step B, all switching elements S1, S2, S3 are held open for a period known as a dead-time. The dead-time is inserted at step B to prevent accidental closure of all three switching elements at the same time, thus shorting out the power supply, which may occur during an overlap period were step C to immediately follow step A. After a suitable dead time, the switching elements S1, S2, S3 are configured as shown in step C of
In step E, switching element S2 is closed. This clears the voltage Vx on Cx by shorting the sensor area 50 to ground. At this stage the measurement circuitry, which in this example is an analogue-to-digital converter configured to measure the voltage applied at input terminal 62 relative to ground, could be used to determine Vc. From Vc, the voltage Vx which was present on the sensor area 50 in step D (i.e. before it was connected to ground) can be determined and the capacitance Cx of the sensor area obtained using the standard voltage divider equations for capacitances in series. However, because Cx is likely to be small, the voltage Vs on the sampling capacitor will also be small. This can make Vs difficult to measure accurately. Accordingly, in this example, the switch control circuitry loops through steps B to E a predetermined number of times in order to build up charge on the sampling capacitor Cs. This provides a larger measurable voltage on Cs due to the increased accumulation of charge and so provides greater accuracy and sensitivity without requiring active amplifiers.
After looping through steps B to E a pre-determined number of times, for example 100 times, the measurement circuitry 54 is configured by the switch control circuitry to measure the voltage Vs at step F with switching element S2 closed. The measured voltage Vs is passed to the processing circuitry 58. Vs depends on the number of loops made through steps B to E shown in
The amount by which the calculated capacitance Cx must exceed Tx to provide a positive detection will depend on how sensitive the designer wishes the control panel to be. For example, where there are a number of closely spaced sensor areas, it will be preferable to require a more significant increase in Cx over the threshold Tx to generate a positive detection so as to avoid one sensor area being unduly affected by a finger being placed over a nearby sensor area. In particular, to minimize false-positive detections, the amount by which Cx must exceed Tx to indicate a positive selection may be set such that a user has to physically touch the glass overlaying a sensitive area he wishes to select before a sufficient increase in capacitance of the sensor area occurs.
Although in the above described switching sequence a measurement of Vs is made after a fixed number of loops through steps B to E, in other examples a variable number of loops can be used. In these examples the measurement circuitry may comprise a comparator arranged to identify when Vs exceeds a pre-defined reference voltage, for example half of +Vr. The number of cycles taken to achieve this is dependent on Cx. Accordingly, a count of the number of loops undertaken before Vs exceeds the reference voltage can be used by the processing circuitry to determine Cx. This scheme has the advantage of using relatively basic comparator circuitry within the measurement circuitry rather than more complex analogue-to-digital converter circuitry.
Although described above as separate circuitry elements, the functionality of the switch control circuitry, the measurement circuitry and the processing circuitry may all be provided by a single general purpose programmable microprocessor or other integrated chip, for example a field programmable gate array (FPGA) or application specific integrated chip (ASIC). It will also be appreciated that corresponding circuitry for other sensor areas can be included in the same package as a single chip as well as circuitry associated with other aspects of the hob, e.g. circuitry associated with the controller 26. Some aspects of the driver circuitry 52 shown in
It will be appreciated that many other configurations of driver circuitry and sensor area can be used, however, circuitry based on the above described principles is relatively simple and effective and has good detection characteristics.
Sensor area 16 is different to the other sensor areas in that it is a position sensitive sensor area and the driver circuitry is correspondingly operable to output a detection signal indicative of the position of a user's finger within this sensor area. This type position sensitive sensor area is sometimes referred to as a slider sensor area. The slider sensor area 16 could comprise a number of closely spaced individual sensor areas having associated driver circuits of the kind shown in
The slider sensor area 16 comprises a resistive sensing strip having end terminations 101 and 102. The sensor area 16 is bonded to the underside of the glass top of the hob. In this example, the resistive sensing strip comprising the sensor area is formed from carbon film. However, other metal films, ITO or SnO, conductive plastics, screen deposited conductors, sputtered conductors etc. could also be used.
The driver circuitry 70 effectively comprises two sensing channels, one associated with each of the terminations 101, 102 of the sensor area 16. The driver circuitry includes first and second measurement circuits 84, 86, first and second switching circuits 80, 82, and switch control circuitry 88. The first switching circuit comprises first, second and third switching elements A, B, C and a first sampling capacitor Cs1 interconnected as shown in the figure. The second switching circuit is similar to the first and comprises fourth, fifth and sixth switching elements A′, B′, C′ and a second sampling capacitor Cs2 interconnected as shown in the figure. The driver circuitry 52 is powered by a single rail DC power supply which operates between a system ground E and a supply voltage +Vr.
The switching elements A, A′, B, B′, C, C′ are driven by control signal lines 90 from the switch control circuitry 88. The sensing channels are made to operate in time-synchronous fashion so that the two sets of switches A, B, C and A′, B′, C′ operate in a substantially simultaneous manner. The sequence of switching is shown in
During an initial phase of operation, at power up for example, calibration readings can be taken of the baseline or ‘background’ signals from both channels to obtain ‘reference’ readings, with no object presumed to be present near the sensor area. These readings may be taken using the same above switching sequences. Once a calibration is taken, only differential readings from each channel are processed in order to calculate position. Further, slow changes in the background level of signals can be compensated for by using ‘drift compensation’ methods that slowly adjust the ‘reference’ levels in a slew-rate limited manner during intervals of non-detection.
To compute the position of an object the two sensor readings are processed according to the following steps assuming that the real time acquired signals are Sig1 and Sig2, and the baseline reference levels are Ref1 and Ref2 respectively:
1) Compute the delta signals ΔSig1, ΔSig2:
A positive detection is assumed to occur only when the total incremental signal strength (ΔSig1+ΔSig2) rises above a minimum threshold value.
P is remarkably free of effects from differently sized objects (e.g. differently sized fingers) and with a linearly increasing resistance along the sensor area an excellent linearity of response is observed.
Controller 26 is operable to receive detection signals from the driver circuitry via the connection 28. The controller 26 is configured to respond to the detection signals is a manner dependent on the detection signal received. For example, if the controller receives detection signals from the driver circuitry which indicate that a user wishes to increase power to heater element 4 c, the controller will act accordingly. This can be achieved by providing an appropriate control signal to the electronically controlled triac 30. Any other conventional electronically controlled power control unit may be used to govern the power supplied to the heater elements. The controller 26 is also configured to drive the information displays 18 a-18 d. In this example the information displays are two-digit LED displays, although LCD or any other type displays could equally be used.
To reduce the chance of unintended activation of certain functions of the hob, for example the switch on function, the controller is operable to only activate these particular functions when a pre-determined combination of sensor areas is appropriately selected. For example, in the control panel 6 shown in
As is common with many appliances, the sensor areas 8 a and 8 b which are used to switch the hob on as described above are also used to switch it off. However, because in general it is less dangerous to have an appliance inadvertently switched off than inadvertently switched on, the controller is configured to switch the hob off when either one of sensor areas 8 a or 8 b is selected. There is no requirement for both sensor areas to be selected within a specified time. In cases where it is desired to prevent an appliance being inadvertently switched off, a similar scheme to that described above for switching on can be similarly employed for the switch off process.
The controller may further be configured to only activate other functions in response to a user making certain pre-determined combinations of multiple selections. This may be done for safety reasons, for example, as with the switch on process, to prevent inadvertent activation of certain functions of the appliance, or may be done to help provide an intuitive and uncluttered control interface.
By way of example, a number of particular operations of the hob and control panel shown in FIGS. 1 to 4 will be described in more detail. It will be appreciated, however, that the layout of the control panel and the preferred mode of operation (e.g. the particular combinations of selections required to activate certain functions described further below) will differ between applications, both according to the functions of the appliance being controlled and the appearance and feel a designer wishes to give the control interface.
As described above, the control panel 6 of
A user switches on the hob by selecting sensor areas 8 a and 8 b in the manner described above. When the hob is first switched on, the default is for no power to be supplied to any of the heating elements 4 a-d. The information displays 18 a-18 d correspondingly all display a value of “00”. In other applications, different initial conditions may be preferred. Now suppose a user then wants to use heating element 4 a at about 25% of its maximum power. The user first activates control of heating element 4 a by placing his finger over heating element selection sensor area 10 a. The driver circuitry senses the user's selection and outputs a corresponding detection signal to the controller. In response to this the controller readies itself for receiving further detection signals concerning the action it will be required to take. The controller also informs the user that control of heating element 4 a has been activated by increasing the brightness of information display 18 a. In other examples a different indication means may be employed, e.g. making the relevant information display flash. The user then places his finger over the slider sensor area 16 to select the amount of power he wishes to apply to heating element 4 a. He does this by placing his finger at an appropriate position along the slider sensor area 16. The slider sensor area is marked “C” for cold at its left-hand end and “H” for hot at its right-hand end. In alternative examples a decal graphic may overlay the sensor area, for example, one which is substantially blue towards the cold end of the slider sensor area and substantially red towards the hot end. The amount of power to be supplied to the heating element 4 a is determined by where the user positions his finger along the slider. To supply maximum power, he positions his finger at the end marked “H”. To supply no power, he positions his finger at the end marked “C”. In the present case, where he wishes to supply 25% power, he places his finger approximately 25% of the distance along the slider sensor area. In this example, he happens to have positioned his finger 24% of the distance along the slider sensor area. The driver circuitry detects this location of the user's finger and outputs a corresponding detection signal to the controller. The controller then configures the electronically controllable triac 30 associated with heating element 4 a to supply 24% of its maximum power. To inform the user of his selection, the controller configures information display 18 a to display the fractional power being supplied to heating element 4 a. With 24% of power being supplied, information display 18 a displays “23” (i.e. 24% represented on a “00” to “99” scale). The user may be satisfied with this approximation to 25% and withdraw his finger. Alternatively, the user may slide his finger slightly towards the hot end of the slider to increase the power supplied to the heating element.
In addition to the information display 18 a, one of a series of LEDs 34 arranged along an edge of the slider sensor area at an appropriate position is illuminated by the controller to allow the user to monitor the presently reported position of his finger on the slider.
After a specified period of time has elapsed with no sensor areas being selected, for example 10 seconds, active control of heater element 4 a is relinquished and information display 18 a returns to the same brightness as the remaining information displays 18 b-d. This prevents subsequent accidental brushing over the slider sensor area 16 from inadvertently adjusting the power supplied to heating element 4 a. If the user wants to re-adjust the power supplied to heating element 4 a when active control of this heating element has been relinquished he again first selects sensor area 10 a to gain active control over the heating element 4 a. On doing this, information display 18 a again brightens and the heating element 4 a may be controlled. The user may now, for example, position his finger over the “double-ring” sensor area to switch on the extension element 30 of heating element 4 a.
If the user now wishes to turn on heating element 4 d at 18% power, he selects sensor area 10 d by placing his finger over that area. This gives him active control of heating element 4 d and allows him to position his finger along the slider sensor area in the appropriate position to set the power level as described above. If he wishes to alter this power he may withdraw his finger and re-position it over the slider sensor area 16 at an appropriate place, or he may simply slide his finger over the slider sensor area 16 to continually adjust the power supplied to heating element 4 d. When the user has set the power level to heating element 4 d at 18%, the control panel appears as shown in
It will be appreciated that the principles described above may be applied to other configurations of control panel which may comprise different configurations of sensor areas designed to be operated in a different manner.
A user switches on the hob 110 by selecting sensor areas 8 a and 8 b in the same manner as described above for the first embodiment of the invention. As before, when the hob is first switched on, the default is for no power to be supplied to any of the heating elements 4 a-d. The information displays 18 a-18 d correspondingly all display a value of “00”. Now suppose a user wants to use heating element 4 a at about 50% of its maximum power. The user first activates control of heating element 4 a by placing his finger over the corresponding heating-element selection sensor area 118 a. As with the first embodiment, the driver circuitry senses the user's selection and outputs a corresponding detection signal to the controller. In response to this the controller readies itself for receiving further detection signals concerning the action it will be required to take. The controller also informs the user that control of heating element 4 a has been activated by increasing the brightness of information display 18 a. The user then places his finger over the rotary position sensor area 120 a to select the amount of power he wishes to apply to heating element 4 a. He does this by placing his finger at an appropriate position around the rotary position sensor area 120 a. The rotary position sensor area is marked with an arrow at the 6 o'clock position to identify a start position. The amount of power to be supplied to the heating element 4 a is determined by how far the user positions his finger around the rotary position sensor area increasing clockwise from the marked arrow. In the present case, where he wishes to supply 50% power, he places his finger approximately 50% of the angular distance around the rotary position sensor area, i.e. at the 12 o'clock position. In this example, he happens to have positioned his finger 48% of the way around the slider sensor area. Information display 18 a is correspondingly configured to display 47 (i.e. 48% on a “00” to “99” scale) and the controller configures the electronically controllable triac associated with heating element 4 a to supply 48% of its maximum power. As before the user may be satisfied with the supplied power and withdraw his finger. Alternatively, he may slide his finger slightly clockwise to increase the power supplied to the heating element.
After a specified period of time has elapsed with no sensor areas being selected, for example 10 seconds, active control of heater element 4 a is relinquished. This aspect of the hob 110 shown in
If the user now wishes to turn on heating element 4 b at 13% power, he selects sensor area 118 b by placing his finger over that area. This gives him active control of heating element 4 b and allows him to position his finger around the rotary position sensor area 120 b in the appropriate position to set the power level as described above. When the user has set the power level to heating element 4 c at 13%, the control panel appears as shown in
It will be appreciated that the principles of the above described invention are not limited to hobs but are applicable to many other types of appliance. For example, similar control panels can be used with many different kinds of domestic appliance such as ovens, grills, washing machines, tumble-dryers, dish-washers, microwave ovens, food blenders, bread makers, drinks machines and so forth. Furthermore, although in the above examples the control panel is formed beneath a glass top of a hob, in other examples the control panel may be remote from the appliance or otherwise mounted, for example on a vertical face of the appliance. It is also possible to provide a control panel similar to those kind described above which is provided separately from an appliance which it may be used to control. For example to provide an upgrade to a pre-existing appliance. It is also possible to provide a control panel which may be configured to operate a range of different appliances. For example, a control panel having a given range of proximity sensor areas which an appliance provider may associated with functions of an appliance as he wishes by appropriately configuring the logic of the controller. For example, by reprogramming the controller.
In addition, although the examples given above are based on capacitance based touch-sensitive controls, other touch-sensitive technologies may also be used. For example resistance-based touch-sensitive screens or infra-red detection based touch-sensitive screens may also be used.
It will be appreciated that although particular embodiments of the invention have been described, many modifications/additions and/or substitutions may be made within the spirit and scope of the present invention.