Capacitive Position Sensor

Abstract

A capacitive touch sensor is provided having sensing path for setting a parameter to a desired value within a range. The sensor has a first mode of operation in which a parameter can be set approximately to a desired value and a second mode in which the value can be refined to the exact amount. In the first mode, the full range of possible values is mapped onto the sensing path and a user touch selects a value within the full range according to its position along the sensing path. In the second mode a finer adjustment is provided for, either by mapping a narrower sub-range of the full range onto the sensing path, or by allowing incremental adjustment of the parameter from the value initially set in the first mode, each incremental unit of adjustment being triggered by the object being displaced through a pre-determined threshold displacement along the sensing path. Switching from the first mode to the second mode is triggered if moving displacement of the object along the sensing path from the first point of touch exceeds a minimum threshold value. This provides an intuitive transition for the user from coarse to fine adjustment.

1 . A capacitive position sensor for setting a parameter or function to a desired value in a range of parameter or function values by determining the position of an object on a capacitive position sensor, the capacitive position sensor comprising:
 a sensing element comprising a sensing path;   at least one terminal connected to the sensing element;   at least one sensing channel connected to the at least one terminal in which the sensing channel is operable to generate a signal indicative of capacitance between the terminal and a system ground;   means to determine a position of an object on the sensing element;   means to further refine the position of the object corresponding to a value in the range of parameter or function values; and   a processor operable to interpret and process the signal to determine the approximate position of an object on the sensing path, the processor being configured to provide a first mode of the capacitive position sensor in which the range of parameter or function values is mapped onto the sensing path and in which the parameter or function can be set to approximately the desired value by a touch of the sensing path at a first point, and a second mode in which displacement of an object on the sensing element adjusts the parameter or function from the value initially set in the first mode, wherein the processor is configured to switch from the first mode to the second mode responsive to capacitive coupling caused by moving displacement of an object along the sensing path in relation to the first point of touch.   
     
     
         2 . The sensor of  claim 1 , wherein the sensing path is formed as a closed loop. 
     
     
         3 . The sensor of  claim 1 , wherein the processor requires said moving displacement to exceed a minimum threshold value in order to initiate a change in mode of the sensor from the first mode to the second mode. 
     
     
         4 . The sensor of  claim 3 , wherein the minimum threshold value is pre-determined and the processor is configurable to set the minimum threshold value at different values depending on the sensitivity required and the parameter or function which is being adjusted. 
     
     
         5 . The sensor of  claim 1 , wherein, in the second mode, the processor effects an incremental change in the parameter or function value when it is sensed that the object has moved along the sensing path by a pre-determined threshold displacement. 
     
     
         6 . The sensor of  claim 1 , wherein, in the second mode, the processor changes the parameter or function value by a number of units based on the number of times the object displacement along the sensing path is sensed to have exceeded the pre-determined threshold displacement. 
     
     
         7 . The sensor of  claim 1 , wherein, in the second mode, the processor maps a narrower sub-range of the range of parameter or function values onto the sensing path around the value of the parameter or function initially set in the first mode. 
     
     
         8 . The sensor of  claim 1 , wherein the processor is further configured such that if a release of touch from the sensing element in the second mode followed by a subsequent re-touching of the sensing element is sensed, then the first mode is activated. 
     
     
         9 . The sensor of  claim 1 , wherein the parameter or function being controlled by the capacitive position sensor is selected from the group: temperature, volume, contrast, brightness, and frequency. 
     
     
         10 . The sensor of  claim 1 , wherein the processor is configured to allow the parameter or function to be controlled to be selected prior to use of the capacitive position sensor. 
     
     
         11 . A control panel of an electronic appliance incorporating a capacitive position sensor according to  claim 1 . 
     
     
         12 . An electronic appliance having a control panel incorporating a capacitive position sensor according to  claim 1 . 
     
     
         13 . The electronic appliance of  claim 12  selected from the group: a cooking oven, microwave oven, television, washing machine, MP3 player, mobile phone, and multimedia device. 
     
     
         14 . A method for setting a parameter or function to a desired value in a range of parameter or function values by determining the position of an object on a capacitive position sensor, the capacitive position sensor comprising: a sensing element comprising a sensing path; at least one terminal connected to the sensing element; at least one sensing channel connected to the at least one terminal in which the sensing channel is operable to generate a signal indicative of capacitance between the terminal and a system ground; means to determine a position of an object on the sensing element; and means to further refine the position of the object corresponding to a value in the range of parameter or function values, the method comprising:
 in a first mode of the capacitive position sensor in which the range of parameter or function values is mapped onto the sensing path bringing an object into proximity with the sensing element at a first point so as to determine a position of the object and thereby initially set the parameter or function to approximately the desired value;   initiating a change in mode of the sensor from the first mode to a second mode responsive to capacitive coupling caused by moving displacement of the object along the sensing path in relation to the first point of touch of the object on the sensing element;   in the second mode displacing the object on the sensing element to adjust the parameter or function from the value initially set to the desired value; and   processing the signal to determine the selected parameter or function value.   
     
     
         15 . The method of  claim 14 , wherein the sensing path is formed as a closed loop. 
     
     
         16 . The method of  claim 14 , wherein said moving displacement is required to exceed a minimum threshold value in order to initiate a change in mode of the sensor from the first mode to the second mode. 
     
     
         17 . The method of  claim 16 , wherein the minimum threshold value is pre-determined and is settable at different values depending on the sensitivity required and the parameter or function which is being adjusted. 
     
     
         18 . The method of  claim 14 , wherein, in the second mode, an incremental change in the parameter or function value is effected by the object moving along the sensing path by a pre-determined threshold displacement. 
     
     
         19 . The method of  claim 14 , wherein, in the second mode, the parameter or function value is changed by a number of units based on the number of times the object displacement along the sensing path exceeds the pre-determined threshold displacement. 
     
     
         20 . The method of  claim 14 , wherein, in the second mode, a narrower sub-range of the range of parameter or function values is mapped onto the sensing path around the value of the parameter or function initially set in the first mode. 
     
     
         21 . The method of  claim 14 , wherein releasing touch from the sensing element in the second mode and then re-touching the sensing element causes the first mode to be activated again. 
     
     
         22 . The method of  claim 14 , wherein the parameter or function being controlled by the capacitive position sensor is selected from the group: temperature, volume, contrast, brightness, and frequency. 
     
     
         23 . The method of  claim 14 , wherein the parameter or function to be controlled is selectable prior to use of the capacitive position sensor.