HK1131311A

HK1131311A - Force invariant touch sensitive actuator

Info

Publication number: HK1131311A
Application number: HK09110663.6A
Authority: HK
Inventors: Robert C. Newman, Jr.; Jeremy Nearhoof; Gregory Altonen; Daniel F. Carmen
Original assignee: Lutron Electronics Co., Inc.
Priority date: 2006-06-20
Filing date: 2007-06-19
Publication date: 2010-01-15

Description

Force invariant touch sensitive actuator

Technical Field

The present invention relates to a load control device for controlling the amount of power delivered from a power source to an electrical load. More particularly, the present invention relates to touch dimmers with touch sensitive devices.

Background

A conventional two-wire dimmer has two terminals: a "hot" terminal for connection to an Alternating Current (AC) power source and a "dimmhot" terminal for connection to a lighting load. Standard dimmers use one or more semiconductor switches, such as triacs or Field Effect Transistors (FETs), to control the current delivered to the lighting load and thereby control the intensity of the light. The semiconductor switch is typically coupled between the hot terminal of the dimmer and the dimmed hot terminal.

Smart wall-mounted dimmers include a user interface, typically having a plurality of buttons for receiving inputs from a user and a plurality of status indicators for providing feedback to the user. These smart dimmers typically include a microcontroller or other processing device for providing advanced control features and feedback options to the end user. An example of a smart dimmer is described in more detail in commonly assigned U.S. patent No. 5248919, entitled LIGHTING CONTROL DEVICE, published 1993, 9/28, which is incorporated herein by reference in its entirety.

Fig. 1 is a front view of a user interface of a prior art smart dimmer switch 10 for controlling the amount of power delivered to a lighting load from an AC power source. As shown, the dimmer switch 10 includes a faceplate 12, a base (bezel)14, an intensity selection actuator 16 for selecting a desired level of light intensity of a lighting load (not shown) controlled by the dimmer switch 10, and a control switch actuator 18. Actuation of the upper portion 16A of the intensity selection actuator 16 increases or raises the light intensity of the lighting load, while actuation of the lower portion 16B of the intensity selection actuator 16 decreases or lowers the light intensity. The intensity selection actuator 16 may control a rocker switch, two separate push button switches, etc. The control switch actuator 18 may control a push button switch or any other suitable type of actuator and typically provides tactile and audible feedback to the user when pressed.

The smart dimmer 10 also includes an intensity level indicator in the form of a plurality of light sources 20, such as Light Emitting Diodes (LEDs). The light sources 20 may be arranged in an array (such as the illustrated line array) that represents a range of light intensity levels of the lighting load being controlled. The intensity level of the lighting load may range from a minimum intensity level, which is preferably the lowest visible intensity, but may be zero or "fully off, to a maximum intensity level, which is typically" fully on ". The light intensity level is typically expressed as a percentage of full light intensity. Thus, when the lighting load is on, the light intensity level is in the range from 1% to 100%.

By illuminating selected ones of the light sources 20 according to the light intensity level, the position of the illuminated light sources within the array provides a visual indication of the light intensity relative to the range when the lamp or lamps being controlled are on. For example, 7 LEDs are illustrated in fig. 1. Illuminating the uppermost LED in the array will indicate that the light intensity level is at or near the maximum. Illuminating the center LED will indicate a light intensity level near the midpoint of the range. In addition, when the lamp or lamps being controlled are off, all of the light sources 18 are illuminated at a low illumination level, while in the on state, the LED representing the current intensity level is illuminated at a higher illumination level. This makes the array of light sources more perceptible to the eyes in a darkened environment, which helps the user locate the switch in a dark room, for example, to actuate the switch to control the lights in the room, and which also provides sufficient contrast between the level indicating LED and the remaining LEDs so that the user perceives the relative intensity level at a glance.

Touch dimmers (or "zipper" dimmers) are known in the art. Touch dimmers typically include a touch-operated input device, such as a resistive or capacitive touch pad. The touch-operated device responds to the force and position of the point actuation on the surface of the device and, in turn, controls the semiconductor switches of the dimmer. An example of a TOUCH dimmer is described in more detail in commonly assigned U.S. patent No. 5196782, entitled TOUCH-OPERATED POWER CONTROL, published 3/23 1993, the disclosure of which is incorporated herein by reference in its entirety.

Fig. 2 is a cross-sectional view of a prior art touch-operated device 30, in particular, the touch-operated device 30 is a membrane voltage divider. The conductive element 32 and the resistive element 34 are closely supported by a co-extensive frame 36. Input voltage V_IntoApplied to the resistive element 34 to provide a voltage gradient across its surface. When pressure is applied to a point 38 along the conductive element 32 (by a finger or the like), the conductive element bends downward and electrically contacts a corresponding point along the surface of the resistive element 34, providing an output voltage V_{Go out}The value of the output voltage is at the input voltage V_IntoAnd the ground. When the pressure is released, the conductive element 32 resumes its original shape and is electrically isolated from the resistive element 34. The touch-operated device 30 is characterized by a contact resistance R between the conductive element 32 and the resistive element 34_{Contact with}. Contact resistance R_{Contact with}The force depends on the actuation of the touch-operated device 30 and is typically substantially small for a typical actuation force.

Fig. 3 is a perspective view of a user interface of a prior art touch dimmer 40. The dimmer 40 includes a touch-operated device 30 located directly behind a faceplate 42. The faceplate 42 includes a flexible region 44 disposed directly above the conductive elements 32 of the touch-operated device 30 to allow a user to actuate the touch-operated device through the faceplate 42. A conventional phase control dimming circuit is disposed within the housing 46 and controls power from the source to the load according to the pressure applied to a selectable point on the flexible region 44. The panel 42 may include selectable indicia 48, 50, 52 to indicate the position of the flexible region 44, the lowest achievable intensity level of the load, and the position of the "off" control, respectively. The optional LED array 54 provides a visual indication of the intensity level of the load. When the load is a light source, there is preferably a linear relationship between the number of illuminated LEDs and the corresponding perceived light level. The flexible region 44 may optionally include a light transmissive region through which the LED array 54 is visible.

It is desirable to provide a touch dimmer that is only responsive to the position of an actuation on an operating area, such as touch dimmingFlexible region 44 of light 40. However, most prior art touch dimmers respond to both the position and force of a point actuation. For example, when the user lightly presses the touch-operated device 30, i.e., with a low actuation force, the contact resistance R_{Contact with}Substantially larger than during normal actuation. Thus, the output of the touch-operated device 30 does not represent the position of actuation, and the dimmer 40 can control the lighting load at an undesirable intensity level. Therefore, there is a need for a touch dimmer having an operating region that is not responsive to a light touch, but only to a point-actuated position.

Disclosure of Invention

According to the present invention, a load control device for controlling the amount of power delivered to an electrical load from an AC power source includes a semiconductor switch, a controller, a touch sensitive actuator, and a stabilizing circuit. A semiconductor switch is for coupling in series electrical connection between the source and the load, the semiconductor switch having a control input for controlling the semiconductor switch between a non-conductive state and a conductive state. A controller is operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state. The touch sensitive actuator has a touch sensitive front surface responsive to point actuations characterized by a position and a force. The touch sensitive actuator has an output operatively coupled to the controller for providing a control signal to the controller. A stabilization circuit is coupled to the output of the touch sensitive actuator. The control signal is responsive only to the position of the point actuation.

According to a second embodiment of the present invention, a load control device for controlling the amount of power delivered to an electrical load from an AC power source includes a semiconductor switch, a controller, a touch sensitive actuator, a usage detection circuit, and a stabilization circuit. The semiconductor switch is for coupling in series electrical connection between the source and the load. The semiconductor switch has a control input for controlling the semiconductor switch between a non-conductive state and a conductive state. A controller is operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between a non-conductive state and a conductive state. The touch sensitive actuator has a touch sensitive front surface responsive to point actuations characterized by a position and a force, the touch sensitive actuator having an output for providing a control signal. A usage detection circuit is operatively coupled between the output of the touch sensitive actuator and the controller for determining whether the point actuation is currently occurring. A stabilization circuit is operatively coupled between the output of the touch sensitive actuator and the controller for stabilizing the control signal from the output of the touch sensitive actuator. The controller is responsive to the control signal when the usage detection circuit has determined that the point actuation is currently occurring.

In accordance with another aspect of the invention, in a control circuit for operating an electrical load in response to an output signal from a touch pad, the touch pad includes an elongated manually touchable resistive area that produces an output signal at an output terminal, the signal being indicative of a position of a manual touch to the touch pad, the control circuit comprising a microprocessor having an input connected to the output signal, and generating an output for controlling the load in response to a manual input to the touch pad, the improvement comprising a filter capacitor connected between the output terminal and a ground terminal, a resistive-capacitive circuit is defined in resistance with the touch pad, the resistive-capacitive circuit characterized by a time constant and adapted to prevent large transient voltage changes due to low pressure touches of the touch pad.

Further, in a manual control structure for generating an electrical signal depending on a position where a touch screen is touched; the control structure comprises a resistive touch screen having control voltages connected to terminals at opposite ends thereof and having output terminals connected to the touch screen at locations where local manual pressure is applied to the screen by a user; a microprocessor having an input connected to said output terminal and generating an output related to said position of said screen receiving said localized manual pressure; the improvement comprises a filter capacitor connected between said output terminal and ground terminal and defining an R/C circuit with a resistance of said touch screen between said location where said screen receives local manual pressure and one of said terminals of said touch screen.

In addition, the present invention provides a process for generating an operating signal from a resistive touch screen, wherein the output voltage on the output terminal is related to both the position on the screen area touched by the user's finger and the pressure of the touch; the process includes generating an x signal in response to a touch at any location on the surface of the screen and a y signal in response to the location of the touch to the screen, and applying the x and y signals to a microprocessor; the microprocessor generates an output signal to the circuit to be controlled only when there is an x output signal at the end of a predetermined sampling interval and also a y output signal.

Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.

Drawings

Fig. 1 is a front view of a user interface of a prior art dimmer;

FIG. 2 is a cross-sectional view of a prior art touch-operated device;

FIG. 3 is a perspective view of a user interface of a prior art touch dimmer;

FIG. 4A is a perspective view of a touch dimmer according to the present invention;

fig. 4B is a front view of the touch dimmer of fig. 4A;

FIG. 5A is a partially assembled cross-sectional view of a base and a touch sensitive device of the touch dimmer of FIG. 4A;

FIG. 5B is a partially exploded cross-sectional view of the base and touch sensitive device of FIG. 5A;

fig. 6 illustrates a force profile (profile) and a cumulative force profile of components of the touch dimmer of fig. 4A;

FIG. 7 is a simplified block diagram of the touch dimmer of FIG. 4A;

FIG. 8 is a simplified schematic diagram of a stabilization circuit and a usage detection circuit of the touch dimmer of FIG. 7 according to a first embodiment of the present invention;

FIG. 9 is a simplified schematic diagram of an audible sound generator of the touch dimmer of FIG. 7;

fig. 10 is a flowchart of a touch dimming procedure performed by the controller of the dimmer of fig. 4A;

fig. 11 is a flowchart of an idle procedure of the touch dimming procedure of fig. 10;

fig. 12A and 12B are flowcharts of an activity maintenance routine of the touch dimming routine of fig. 10;

fig. 13 is a flowchart of a release procedure of the touch dimming procedure of fig. 10;

14A and 14B are simplified schematic diagrams of circuitry for a four-wire touch sensitive device and controller for the touch dimmer of FIG. 4A, according to a second embodiment of the present invention;

FIG. 15A is a simplified schematic diagram of the circuitry of a four-wire touch sensitive device and controller for the touch dimmer of FIG. 4A, according to a third embodiment of the present invention;

fig. 15B is a simplified block diagram of a dimmer according to a fourth embodiment of the present invention;

FIG. 15C is a simplified schematic diagram of the circuitry for the three-wire touch sensitive device and controller of the dimmer of FIG. 15B;

fig. 16A is a perspective view of a touch dimmer according to a fifth embodiment of the present invention;

fig. 16B is a front view of the touch dimmer of fig. 16A;

fig. 17A is a bottom cross-sectional view of the touch dimmer of fig. 16B;

FIG. 17B is an enlarged partial view of the bottom cross-sectional view of FIG. 17A;

fig. 18A is a left side cross-sectional view of the touch dimmer of fig. 16B;

FIG. 18B is an enlarged partial view of the left side cross-sectional view of FIG. 18A;

fig. 19 is a perspective view of a display printed circuit board of the dimmer of fig. 16A; and

FIG. 20 is an enlarged partial bottom cross-sectional view of a thin touch sensitive actuator in accordance with a sixth embodiment of the present invention.

Detailed Description

The foregoing summary, as well as the following detailed description of preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.

Fig. 4A and 4B are a perspective view and a front view, respectively, of a touch dimmer 100 according to the present invention. The dimmer 100 includes a faceplate 102, i.e., a cover plate, the faceplate 102 having a flat front surface 103 and an opening 104. The opening 104 may define a standard industry-defined opening, such as a conventional opening or a decorative opening, or another uniquely sized opening as shown in FIG. 4A. A bezel 106 having a flat touch-sensitive front surface 108 extends through the opening 104 of the faceplate 102. The front surface 108 of the bezel 106 rests directly on the touch sensitive device 110 (shown in fig. 5A and 5B), i.e., the touch sensitive element, such that a user of the dimmer 100 actuates the touch sensitive element 110 by pressing on the front surface 108 of the bezel 106. As shown in fig. 4A, the front surface 108 of the bezel 106 is substantially flush with the front surface 103 of the faceplate 102, i.e., the plane of the front surface 108 of the bezel 106 is coplanar with the plane of the front surface 103 of the faceplate 102. However, the bezel 106 may extend through the opening 104 of the faceplate 102 such that the front surface 108 of the bezel is disposed in a plane above the plane of the front surface 103 of the faceplate 102. The panel 102 is connected to an adapter 109 and the adapter 109 is connected to a clip (not shown). The clip is adapted to mount the dimmer 100 to a standard electrical wallbox (wallbox).

The dimmer 100 also includes a visual display, such as a plurality of status markers 112 disposed in a linear array along the edge of the front surface 108 of the base 106. The status indicator 112 is preferably illuminated from behind by a status indicator 114, the status indicator 114 being, for example, a Light Emitting Diode (LED) and located inside the dimmer 100 (see fig. 7). The dimmer 100 preferably includes a light pipe (not shown) having a plurality of light conductors for conducting light from a status indicator 114 inside the dimmer to a marker 112 on the front surface 108 of the base 106. The status indicators 114 behind the markers 112 are preferably blue. As shown in fig. 4A and 4B, the dimmer 100 includes seven (7) status identifiers 112. However, the dimmer 100 may include any number of status identifiers. Further, the status identifiers 112 may be disposed in a vertical line array along the center of the front surface 108 of the bezel 106. Due to the gap behind the front face, the identifier 112 may include a shadow on the appearance of the front face 108.

The front side 108 of the bezel 106 also includes an icon 116. The icon 116 may be any kind of identifier, such as, for example, a dot. Upon actuation of the lower portion of the front surface 108 surrounding the icon 116, the dimmer 100 causes the connected lighting load 208 (fig. 7) to change from on to off (and vice versa), i.e., to toggle. Preferably, the blue status indicator and the orange status indicator are disposed directly behind the icon 116 such that the icon 116 is illuminated with blue light when the lighting load 208 is on and the icon 116 is illuminated with orange light when the lighting load is off. Actuation of the upper portion of the front surface 108, i.e., the portion above the portion surrounding the icon 116, causes the intensity of the lighting load 208 to change. The status indicators 114 behind the status indicator 112 are illuminated to display the intensity of the lighting load 208. For example, if the lighting load 208 is at 50% of the lighting intensity, the middle status indicator will be illuminated. Preferably, the dimmer 100 is not responsive to actuation in the keep out zone 118 of the front surface 108. The keepout region 118 prevents inadvertent actuation of undesired portions of the front surface 108 during operation of the dimmer 100.

The dimmer 100 also includes an air gap switch actuator 119. Pulling the airgap switch actuator 119 opens a mechanical airgap switch 219 (fig. 7) inside the dimmer 100 and disconnects the lighting load 208 from the connected AC voltage source 204 (fig. 7). The airgap switch actuator 119 extends sufficiently above only the front face 103 of the faceplate 102 so that a user's fingernail can grasp it. The electronic circuitry of the dimmer 100, which will be described in more detail below, is mounted on a Printed Circuit Board (PCB) (not shown). The PCB is housed in a housing (not shown), i.e., an enclosed volume, that is coupled to the yoke of the dimmer 100.

Fig. 5A is a partially assembled cross-sectional view of the base 108 and the touch sensitive device 110 of the dimmer 100 according to the present invention, and fig. 5B is a partially exploded view of the base 108 and the touch sensitive device 110 of the dimmer 100 according to the present invention. The touch sensitive device 110 comprises, for example, a resistive divider and operates in a similar manner to the touch-operated device 30 of the prior art touch dimmer 40. The touch sensitive device 110 includes a conductive element 120 and a resistive element 122 supported by a spacing frame 124. However, the touch sensitive device 100 may include a capacitive touch screen or any other type of touch responsive element. The touch sensitive device is commonly referred to as a touch pad or touch screen.

An opening 128 in the back of the base 106 receives the elastomer 126. The elastomer 126 is disposed between the bezel 106 and the touch sensitive device 110 such that a press against the bezel's front surface 108 is transmitted to the conductive elements 120 of the touch sensitive device 110. Preferably, the elastomer 126 is made of rubber and has a thickness of 0.040 ". The elastomer 126 preferably has a hardness (durometer) of 40A, but may have a hardness in the range of 20A to 80A. The conductive element 120 and the resistive element 122 and the elastomer 126 of the touch sensitive device 110 are preferably made of a transparent material so that light from the plurality of status indicators 114 inside the dimmer 100 can shine through the touch sensitive device 110 and the elastomer 126 to the front surface 108 of the bezel 106.

The dashed lines in FIG. 4B indicate the position and size of the touch sensitive device 110. The length of the touch sensitive device 110 is L₁And a width of W₁The length and width being greater than the length L of the front surface 108 of the submount 106₂And width W₂And is larger. Thus, the first area A of the surface of the touch sensitive device 110₁(i.e. A)₁＝L₁·W₁) A second area A larger than the front surface of the susceptor 106₂(i.e. A)₂＝L₂·W₂). Orthographic projection to a first area A₁Second area A of₂Is covered with the first area A₁The wrap-around, such that point actuations at any point on the front surface 108 of the bezel 106 are transmitted to the conductive element 120 of the touch sensitive device 110. As shown in FIGS. 4A and 4B, the length L of the front surface 108 of the submount 106₂Specific width W₂About four (4) times greater. Preferably, the length L of the front surface 108 of the submount 106₂Specific width W₂About four (4) to six (6) times greater. Alternatively, the front surface 108 of the base 106 may be disposed in an opening of a decorative style panel.

Fig. 6 illustrates a force profile of the components of the dimmer 100 illustrated in fig. 5A and 5B and an accumulated force profile of the touch sensitive device 110 of the dimmer 100. Each force profile shows the force required to actuate the touch sensitive device 110 for the location of the point actuation. The force profile represents the amount of force required to displace the element by a given amount. While the force profile is shown in fig. 6 for the width of the dimmer 100, a similar force profile is also provided along the length of the assembly.

Fig. 6(a) shows the force distribution of the susceptor 106. The base 106 has substantially thin sidewalls 129, e.g., 0.010 "thick, such that the base 106 exhibits a substantially flat force distribution. Fig. 6(b) shows a force distribution of the touch sensitive device 110. Due to the spacer frame 124, the force required to actuate the touch sensitive device 110 increases near the edges. Fig. 6(c) shows the force distribution of the elastic body 126. The force distribution of the resilient body 126 is substantially flat, i.e., a force at any point on the front side of the resilient body 126 will result in a substantially equal force at a corresponding point on the back side.

Fig. 6(d) is the total force profile of the touch dimmer 100. The individual force profiles shown in fig. 6(a) -6 (c) are summed to produce an overall force profile. The total force is distributed over a second area A of the front surface 108 of the susceptor 106₂Is substantially flat. This means that at all points of the front surface 108 of the bezel 106, even near the edges, a substantially equal minimum actuation force f is required to actuate the touch sensitive device 110_MIN. Thus, the dimmer 100 of the present invention provides the largest operating area in the opening of the faceplate, i.e., the second area a of the front surface 108 of the base 106₂This is an improvement over prior art touch dimmers. Minimum actuation force f_MINSubstantially equal at all points on the front surface 108 of the submount 106. For example, minimum actuation force f_MINAnd may be 20 grams.

Fig. 7 is a simplified block diagram of a touch dimmer 100 according to the present invention. The dimmer 100 has a hot terminal 202 connected to an AC voltage source 204 and a dimmed hot terminal 206 connected to a lighting load 208. The dimmer 100 employs a bidirectional semiconductor switch 210 coupled between the hot terminal 202 and the dimmed hot terminal 206 to control the current through the lighting load 208 and thereby control the intensity of the lighting load 208. The semiconductor switch 210 has a control input (or gate) connected to a gate drive circuit 212. The input to the gate causes the semiconductor switch 210 to selectively conduct or not conduct, which in turn controls the power supplied to the lighting load 208. The gate drive circuit 212 provides a control input to the semiconductor switch 210 in response to a control signal from the controller 214. The controller 214 may be any suitable controller, such as a microcontroller, microprocessor, Programmable Logic Device (PLD), or Application Specific Integrated Circuit (ASIC).

The zero-crossing detection circuit 216 determines zero-crossing points of the AC source voltage from the AC power source 204. The zero crossing is defined as being at eachThe time at which the AC source voltage transitions from positive to negative or negative to positive at the beginning of a half cycle. The zero-crossing information is set as an input to the controller 214. The controller 214 generates the gate control signals to operate the semiconductor switch 210 to provide the voltage from the AC power source 204 to the lighting load 208 at a predetermined time relative to the zero-crossing point of the AC waveform. Power supply 218 generates a Direct Current (DC) voltage V_CCE.g., 5 volts, to power the controller 214 and other low voltage circuitry of the dimmer 100.

The touch sensitive device 110 is coupled to the controller 214 through the stabilizing circuit 220 and the usage detection circuit 222. The stabilizing circuit 220 is used to stabilize the voltage output of the touch sensitive device 110. Thus, the voltage output of the stabilizing circuit 220 does not depend on the magnitude of the force of the point actuation on the touch sensitive device 110, but only on the location of the point actuation. The usage detection circuit 222 is used to detect when a user is actuating the front surface 108 of the dimmer 100. The controller 214 is used to couple or decouple the stabilization circuit 220 and the usage detection circuit 222 to the output of the touch sensitive device 110. The controller is also operable to receive signals from the stabilization circuit 220 and the usage detection circuit 222. Preferably, the stabilization circuit 220 has a slow response time, while the usage detection circuit 222 has a fast response time. Thus, the controller 214 is operable to control the semiconductor switch 210 in response to a control signal provided by the stabilizing circuit 220 when the usage detection circuit 222 has detected actuation of the touch sensitive device 110.

The controller 214 is configured to drive a plurality of status indicators 114, such as Light Emitting Diodes (LEDs), disposed behind the markers 112 on the front 108 of the dimmer 100. The status indicators 114 also include a blue status indicator and an orange status indicator disposed directly behind the icon 116. The blue status indicator and the orange status indicator may be implemented as separate blue and orange LEDs, respectively, or as a single bi-color LED.

The dimmer 100 also includes an audible sound generator 224 coupled to the controller 214, whereby the controller is operative to cause the sound generator to generate audible sound in response to actuation of the touch sensitive device 110. The memory 225 is coupled to the controller 214 and is used to store control information for the dimmer 100.

FIG. 8 is a simplified schematic diagram of the circuitry for the touch sensitive device 110 and the controller 214 (i.e., the stabilizing circuit 220 and the usage detection circuit 222) in accordance with the first embodiment of the present invention. The resistive element 122 of the touch sensitive device 110 is coupled to the DC voltage V of the power supply 218_CCAnd circuit common, so that DC voltage V_CCA bias voltage is provided to the touch sensitive device. For example, resistive element 122 may have a resistance R of 7.6k Ω_E. The location of contact between the conductive element 120 and the resistive element 122 of the touch sensitive device 110 is determined by the location of the point actuation on the front surface 108 of the bezel 106 of the dimmer 100. The conductive element 120 is coupled to a stabilization circuit 220 and a usage detection circuit 222. As shown in fig. 7, the touch sensitive device 110 of the dimmer 100 of the first embodiment is a three-wire device, i.e., the touch sensitive device has three connections or electrodes. The touch sensitive device provides an output that represents the position of the point actuation along the Y-axis, i.e., the longitudinal axis of the dimmer 100 as shown in fig. 4B.

The stabilizing circuit 220 includes a large-scale capacitor C230 (i.e., a capacitor having a large capacitance value) and a first switch 232. The controller 214 is configured to control the first switch 232 between a conductive state and a non-conductive state. When the first switch 232 is turned on, the capacitor C230 is coupled to the output of the touch sensitive device 110, so that the output voltage is filtered by the capacitor C2320. When a touch is present, the voltage on capacitor C230 will be caused to reach a steady state voltage representing the location of the touch on the front side 108. When there is no touch, the voltage on the capacitor will remain at the voltage representing the location of the last touch. The touch sensitive device 110 and the capacitor C230 form a sample-and-hold circuit. The response time of the sample-and-hold circuit is determined by the resistance R of the touch sensitive device_D(i.e., resistance R of the resistive element_EAnd contact resistance R_C) And the capacitance of capacitor C230. During typical actuation, the contact resistance R_CRatio R_EIs small so that the first charging time constant τ is₁Approximately equal to R_EC230. This time constant τ₁Preferably 13ms, but can be any value between 6ms and 15 ms.

When a light or momentary press is applied to the touch sensitive device 110, the capacitor C230 will continue to hold the output at a voltage that represents the location of the last touch. During the release of the touch sensitive device 110, a transient event may occur that produces an output voltage that represents a location that is different from the actual touch location. Is greater than the first charging time constant tau₁A short momentary press will not substantially affect the voltage on capacitor C230 and therefore will not substantially affect the sensing of the last actuated position. During light pressing, due to higher contact resistance R_CSecond charging time constant τ₂Will be substantially longer than during normal compression, i.e. substantially longer than the first time constant τ₁Is large. However, the steady state value of the voltage on capacitor C230 will be the same as for a normal press at the same location. Thus, the output of the stabilizing circuit 220 represents only the position of the point of actuation of the touch sensitive device 110.

The usage detection circuit 222 includes a resistor R234, a capacitor C236, and a second switch 238, which is controlled by the controller 214. When the switch 238 is turned on, the parallel combination of the resistor R234 and the capacitor C236 is coupled to the output of the touch sensitive device 110. Preferably, the capacitor C236 has substantially a small capacitance C₂₃₆So that the capacitor C236 charges substantially quickly in response to all point actuations on the front surface 108. Resistor R234 allows capacitor C236 to discharge quickly when switch 238 is non-conductive. Thus, the output of the usage detection circuit 222 represents the instantaneous usage of the touch sensitive device 110.

The controller 214 controls the switches 232, 238 in a complementary manner. When the first switch 232 is conductive, the second switch 238 is non-conductive, and vice versa. At each half cycle of the voltage source 204, the controller 214 is on for a short period of time t_{Use of}The second switch 238 is controlled to be on once to determine if the user is actuating the front side 108. Preferably, the short period t_{Use of}Approximately 100 musec or 1% of a half cycle (assuming each half cycle is 8.33msec long). For the rest of the time, the first switch 232 is turned on, and the capacitor C230 is used to charge accordingly. When the first switch 232 is notWhen conducting and the second switch 238 is conducting, the large-scale capacitor C230 of the stabilizing circuit 220 cannot discharge at a significant rate, and thus the voltage across the capacitor C230 will not change significantly when the controller 214 determines whether the touch sensitive device 110 is being actuated by using the detection circuit 222. Although the stabilization circuit 220 is shown and described herein as a hardware circuit, the controller 214 could alternatively provide the filtering function of the stabilization circuit entirely in software.

Fig. 9 is a simplified schematic diagram of the audible sound generator 224 of the dimmer 100. Audible sound generator 224 uses an audio power amplifier Integrated Circuit (IC)240 (e.g., part number TPA721, manufactured by Texas Instruments, inc.) to generate sound from a piezoelectric or magnetic speaker 242. The amplifier IC240 is coupled to the DC voltage V_CC(pin 6) and circuit common (pin 7) to power the amplifier IC. Capacitor C244 (preferably having a capacitance of 0.1 μ F) is coupled at DC voltage V_CCAnd circuit common to disconnect the supply voltage and ensure that the output Total Harmonic Distortion (THD) is as low as possible.

The audible sound generator 224 receives a sound enable signal 246 from the controller 214. The sound enable signal 246 is provided to an enable pin (i.e., pin 1) on the amplifier IC240 so that the audible sound generator 224 will be used to generate sound when the sound enable signal is at a logic high level.

The audible sound generator 224 also receives a sound wave signal 248 from the controller 214. The sound wave signal 248 is an audio signal that is amplified by the amplifier IC240 to produce the appropriate sound at the speaker 242. The acoustic wave signal 248 is first filtered by a low pass filter comprising a resistor R250 and a capacitor C252. Preferably, resistor R250 has a resistance of 1k Ω and capacitor C252 has a capacitance of 0.1 nF. The filtered signal is then passed through capacitor C254 to produce the input signal V_Into. Capacitor C254 allows the amplifier IC to input the signal V_IntoBiased to a suitable DC level for optimum operation and preferably has a capacitance of 0.1 muf. Through an input resistor R_IWill input signal V_IntoIs provided to the amplifier IC240The negative input (pin 4). The positive input (pin 3) and the bypass pin (pin 2) of the amplifier IC240 are coupled to circuit common through a bypass capacitor C256 (preferably having a capacitance of 0.1 muf).

The output signal V of the amplifier IC240 is generated from the positive output (pin 5) to the negative output (pin 8)_{Go out}And provides it to the speaker 242. The negative input (pin 4) passes through an output resistor R_FCoupled to the positive output (pin 5). The gain of the amplifier IC240 is controlled by the input resistor R_IAnd a feedback resistor R_FIs set, i.e.

Gain is V_{Go out}/V_Into＝—2·(R_F/R_I)

Preferably, the input resistance R_IAnd an output resistor R_FEach having a resistance of 10k omega so that the gain of the amplifier IC240 is negative two (-2).

Fig. 10 is a flowchart of a touch dimming procedure 300 executed by the controller 214 of the dimmer 100 according to the present invention. Preferably, the touch dimmer procedure 300 is invoked from the main loop of the software of the controller 214 once every half cycle of the AC voltage source 204. The touch dimming procedure 300 selectively executes one of three procedures depending on the state of the dimmer 100. If the dimmer 100 is in the "idle" state (i.e., the user is not actuating the touch sensitive device 110) at step 310, the controller 214 executes the idle procedure 400. If the dimmer 100 is in the "active hold" state (i.e., the user is actuating the touch sensitive device 110) at step 320, the controller 214 executes the active hold routine 500. If the dimmer 100 is in the "released" state (i.e., the user has recently ceased actuating the touch sensitive device 110) at step 330, the controller 214 executes a release routine 600.

FIG. 11 is a flow chart of an idle procedure 400 according to the present invention. The controller 114 uses the "sound flag" and the "sound counter" to determine when to cause the audible sound generator 224 to generate an audible sound. The purpose of the sound flag is to cause the controller 214 to generate a sound the first time the activehold procedure 500 is executed after an idle state. If the sound is setFlag, the controller 214 will cause a sound to be generated. The sound counter is used to ensure that the controller 214 does not cause the audible sound generator 224 to generate audible sounds too frequently. The sound counter preferably has a maximum sound counter value S_MAXFor example about 425 msec. Thus, there is a gap of about 425msec between the production of audible sounds. During the release procedure 600, a sound counter is started, as described in more detail below. Referring to fig. 11, upon entering the idle state, if the sound flag is not set at step 402, the controller 214 sets the sound flag at step 404.

The controller 214 uses the "LED counter" and the "LED mode" to control the status indicators 114 (i.e., LEDs) of the dimmer 100. The controller 214 uses the LED counter to determine the predetermined time t since the touch sensitive device 110 was actuated_LEDWhen it is expired. When the predetermined time t is_LEDUpon expiration, the controller 214 will change the LED mode from "active" to "inactive". When the LED mode is "active," the status indicators 114 are controlled such that one or more of the status indicators are illuminated to a bright level. When the predetermined time t is_LEDUpon expiration, the LED mode becomes "inactive," i.e., the status indicators 114 are controlled such that one or more of the status indicators are illuminated to a dim level. Referring to FIG. 11, if the LED counter is less than the maximum LED counter value L at step 410_MAXThen the LED counter is incremented at step 412 and the process moves to step 418. However, if the LED counter is not less than the maximum LED counter value L_MAXThen the LED counter is cleared at step 414 and the LED mode is set to inactive at step 416. Since the touch dimming procedure 300 is performed once every half cycle, the predetermined time t_LEDPreferably equal to

t_LED＝T_HALF·L_MAX

Wherein T is_HALFA half-cycle period.

Next, the controller 214 reads the output of the usage detection circuit 222 to determine whether the touch sensitive device 110 is being actuated. Preferably, the usage detection circuit 222 is monitored once every half cycle of the voltage source 204. At step 418, the controller 214 opens the switch 232 and closes the switch 238 to couple the resistor R234 and the capacitor C236 to the output of the touch sensitive device 110. At step 420, the controller 214 determines the DC voltage at the output of the usage detection circuit 222, preferably by using an analog-to-digital converter (ADC). Next, at step 422, the controller 214 closes the switch 232 and opens the switch 238.

At step 424, if there is activity on the front surface 108 of the dimmer 100, i.e., if the DC voltage determined at step 420 is above the predetermined minimum voltage threshold, then at step 426, the "activity counter" is incremented. Otherwise, the activity counter is cleared at step 428. The controller 214 uses the activity counter to determine whether the DC voltage determined at step 420 is the result of a point actuation of the touch sensitive device 110 and not noise or some other undesirable impulse. The use of activity counters is similar to the "debounce" procedure for mechanical switches, which is well known in the art. If the activity counter is not less than the maximum activity counter value A at step 430_MAXThen the dimmer state is set to the active hold state at step 432. Otherwise, at step 434, the process simply exits.

Fig. 12A and 12B are flowcharts of the activehold procedure 500, which is performed 500 once every half-cycle when the touch sensitive device 110 is being actuated (i.e., when the dimmer 100 is in an activehold state). First, it is determined whether the user has stopped using (i.e., released) the touch sensitive device 110. The controller 214 opens the switch 232 and closes the switch 238 at step 510 and reads the output of the usage detection circuit 222 at step 512. At step 514, the controller 214 closes the switch 232 and opens the switch 238. If there is no activity on the front surface 108 of the dimmer 100 at step 516, the controller 214 increments the "inactivity counter" at step 518. The controller 214 uses the inactivity counter to make sure that the user has not actuated the touch sensitive device 110 before entering the release mode. If the inactivity counter is less than the maximum inactivity counter value I at step 520_MAXThen the process exits at step 538. Otherwise, the dimmer state is set to the released state at step 522State, and then exit the process.

If there is activity on the touch sensitive device 110 at step 516, the controller 214 reads the output of the stabilizing circuit 220, which represents the location of the point actuation on the front surface 108 of the dimmer 100. Because switch 232 is conductive and switch 238 is non-conductive, controller 214 determines the DC voltage at the output of stabilization circuit 220, preferably using an ADC, at step 524.

Next, the controller 214 uses the buffer to "filter" the output of the stabilization circuit 220. When the user actuates the touch sensitive device 110, the capacitor C230 will be at a first time constant τ as previously described₁The determined period of time is charged to a near steady state voltage, which represents the position of the actuation on the front surface 108. Because the voltage on capacitor C230 (i.e., the output of the stabilizing circuit 220) is increasing at this time, the controller 214 delays for a predetermined period of time, preferably about three (3) half cycles, at step 525.

When the user's finger is removed from the front surface 108 of the base 106, a subtle change in the force and position of the point actuation occurs, i.e., a "finger slide-off" event occurs. Thus, the output signal of the touch sensitive device 110 is no longer representative of the position of the point actuation. To prevent the controller 214 from processing the readings during the finger roll-off event, the controller 214 saves the readings in a buffer and processes the readings after a delay, for example, six half cycles later. Specifically, when the delay ends at step 525, the controller 214 rotates the new reading (i.e., from step 524) into the buffer at step 526. If the buffer has at least six readings at step 528, the controller 214 averages the readings in the fifth and sixth locations in the buffer to generate touch position data at step 530. In this manner, when the user stops actuating the touch sensitive device 110, the controller 214 detects this change at step 516 and sets the dimmer state to the release state at step 522 before the controller processes the readings stored in the buffer around the transition time of the touch sensitive device.

In step 532, controller 114 determines the touch location from step 530Whether the data is in the keep out region 118 (as shown in fig. 4B). If the touch location data is in the disabled area 118, the active hold routine 500 simply exits at step 538. Otherwise, it is determined whether sound should be generated at step 534. In particular, if the sound flag is set and if the sound counter has reached the maximum sound counter value S_MAXThe controller 214 drives the sound enable signal 246 high and provides the sound wave signal 248 to the audible sound generator 224 to generate the sound at step 535. Further, the sound flag is cleared at step 536 such that no sound is generated as long as the dimmer 100 remains in the active hold state.

If the touch position data is in the trigger area, i.e., the lower portion of the front surface 108 of the bezel 106 surrounding the icon 116 (as shown in FIG. 4A), the controller 214 processes the actuation of the touch sensitive device 110 as a trigger at step 540. If the lighting load 208 is currently off at step 542, the controller 214 turns the lighting load on. Specifically, the controller 214 illuminates the icon 116 with the blue status indicator at step 544 and dims the lighting load 208 to a preset level, i.e., a desired lighting intensity of the lighting load, at step 546. If the lighting load is currently on at step 542, the controller 214 turns on the orange status indicator behind the icon 116 at step 548 and dims the lighting load 208 to off at step 550.

If the touch position data is not in the trigger area at step 540, the controller 214 scales the touch position data at step 552. The output of the stabilizing circuit 220 is a DC voltage between a maximum value and a minimum value, the maximum value being substantially the DC voltage V_CCThe minimum value corresponds to the DC voltage provided by the touch sensitive device 110 when the user actuates the lower end of the upper portion of the front surface 108 of the bezel 106. The controller 214 scales this DC voltage to a value between off (i.e., 1%) and full intensity (i.e., 100%) of the lighting load 208. At step 554, the controller 214 adjusts the load 208 to the scaled level generated at step 552.

Next, the controller 214 changes the status indicator 114 disposed behind the markers 112 on the front surface 108 of the bezel 106. As the user actuates the touch sensitive device 110 to change the intensity of the lighting load 208, the controller 214 determines whether to change the currently illuminated status indicator 114. Because there are seven (7) status indicators to indicate an intensity between 1% and 100%, the controller 214 may illuminate the first status indicator (i.e., the lowest status indicator) to represent an intensity between 1% and 14%, illuminate the second status indicator to represent an intensity between 15% and 28%, and so on. The seventh status indicator (i.e., the highest status indicator) may be illuminated to represent an intensity between 85% and 100%. Preferably, the controller 214 controls the status indicators 114 using hysteresis such that successive status indicators do not toggle back and forth when the user actuates the front surface 108 at the boundary of the two aforementioned intensity zones.

Referring to FIG. 12B, it is determined whether a change to the illuminated status indicator is required at step 556. If the current LED (the result of the touch location data of step 530) is the same as the previous LED, no change to the LED is required. The current LED is set to be the same as the previous LED at step 558, the hysteresis counter is cleared at step 560, and the process exits at step 570.

If the current LED is different from the previous LED at step 556, the controller 214 determines if the LED should be changed. Specifically, at step 562, the controller 214 determines whether the current LED should be changed when the light level is changed by 2% from the light level indicated by the touch position data. If not, the hysteresis counter is cleared at step 560 and the process exits at step 570. Otherwise, the hysteresis counter is incremented at step 564. If the hysteresis counter is less than the maximum hysteresis counter value H at step 566_MAXThe process exits at step 570. Otherwise, the LEDs are changed accordingly based on the touch position data at step 568.

Fig. 13 is a flow chart of a release routine 600 that is performed by the controller 214 after the dimmer state is set to the release state at step 522 of the activehold routine 500. Next, the sound counter is reset at step 612 to ensure that no sound is produced, e.g., preferably for 18 half cycles. At step 618, it is determined whether the dimmer 100 is currently performing a dim-to-off. If not, the current level is saved as a preset level in the memory 225 at step 620. Otherwise, the desired illumination intensity is set to off at step 622, a long fade decrement is started at step 624, and the preset level is saved as off in the memory 225.

Fig. 14A and 14B are simplified schematic diagrams of circuitry for a four-wire touch sensitive device 710 and a controller 714 according to a second embodiment of the present invention. The four-wire touch sensitive device 710 has four connections (i.e., electrodes) and provides two outputs: a first output representing a position of the point actuation along the Y-axis (i.e., the longitudinal axis of the dimmer 100 shown in fig. 4B) and a second output representing a position of the point actuation along the X-axis (i.e., an axis perpendicular to the longitudinal axis). The output provided by the four-wire touch sensitive device 710 is dependent on the DC voltage V_CCHow to connect to the touch sensitive device. The stabilization circuit 720 is adapted to be coupled to a first output and the usage detection circuit 722 is adapted to be coupled to a second output.

The controller 714 controls the three switches 760, 762, 764 to correspondingly connect the touch sensitive device 710 to the DC voltage V_CC. When the switches 760, 762, 764 are connected in position a shown in fig. 14A, the DC voltage V_CCCoupled across the Y-axis resistor and the X-axis resistor provides an output to the stabilization circuit 720. When the switches 760, 762, 764 are connected in position B shown in fig. 14B, the DC voltage V_CCCoupled across the X-axis resistor and the Y-axis resistor provides an output to the usage detection circuit 722. Because the controller 714 provides an output signal to control whether the stabilizing circuit 720 or the usage detection circuit 722 is coupled to the touch sensitive device 110, the software executed by the controller 714 is the same as the software executed by the controller 214 shown in FIGS. 10-13.

Fig. 15A is a simplified schematic diagram of the circuitry for a four-wire touch sensitive device 710 and a controller 814 according to a third embodiment of the present invention. The controller 814 is used to read the location of point actuations along the Y-axis and the X-axis on the four-wire touch sensitive device 710. In determining the position along the Y-axis, the controller 814 operates the same as the controller 714 shown in fig. 14A and 14B by controlling the switches 760, 762, 764 as described above.

An additional stabilization circuit 870 is provided for determining the position of the point actuation along the X-axis. The additional stabilization circuit 870 includes a large-scale capacitor C872. The controller 814 controls a switch 874 to selectively switch the output of the X-axis between the usage detection circuit 722 and the additional stabilization circuit 870. The control circuit 814 controls the switch 874 in a manner similar to the manner in which the controller 214 controls the switches 232, 238 (as shown in fig. 8).

Fig. 15B is a simplified block diagram of a dimmer 1000 according to a fourth embodiment of the present invention. Fig. 15C is a simplified schematic diagram of the circuitry for the three-wire touch sensitive device 110 and the controller 1014 of the dimmer 1000 according to the fourth embodiment. The dimmer 1000 includes only the stabilization circuit 1020 and no usage detection circuit. The stabilizing circuit 1020 includes only a large-scale capacitor C1030. Thus, the controller 1014 is not used to control the stabilizing circuit 1020, but is responsive to the touch sensitive device 100 only through the stabilizing circuit.

Fig. 16A and 16B are a perspective view and a front view, respectively, of a touch dimmer 900 according to a fifth embodiment of the present invention. Fig. 17A is a bottom cross-sectional view of the dimmer 900, and fig. 17B is an enlarged partial bottom cross-sectional view of the dimmer 900. Fig. 18A is a left side cross-sectional view of the dimmer 900, and fig. 18B is an enlarged partial left side cross-sectional view of the dimmer 900.

The touch dimmer 900 includes a thin touch sensitive actuator 910, the thin touch sensitive actuator 910 including an actuation member 912 extending through a base 914. The dimmer 900 also includes a faceplate 916 having a non-standard opening 918 and mounted on an adapter 920. The base 914 is received behind the faceplate 916 and extends through the opening 918. The adapter 920 is attached to a clip 922, the clip 922 being adapted to mount the dimmer 900 to a standard electrical wallbox. A main Printed Circuit Board (PCB)924 is mounted inside the housing 92 and includes some of the circuitry of the dimmer 200, such as the semiconductor switch 210, the gate drive circuit 212, the controller 214, the zero-crossing detection circuit 216, the power supply 218, the stabilization circuit 220, the usage detection circuit 222, the audible sound generator 224, and the memory 225 of the dimmer 200. The thin touch sensitive actuator 910 preferably extends 1/16 "out of the panel, i.e. a height of 1/16", but the height may be in the range of 1/32 "to 3/32". Preferably, the touch sensitive actuator 910 is 3-5/8 "in length and 3/16" in width. However, the length and width of the touch sensitive actuator 910 may be in the range of 2-5/8 "to 4" and 1/8 "to 1/4", respectively.

The touch sensitive actuator 910 is used to contact a touch sensitive device 930 inside the touch dimmer 900. The touch sensitive device 930 is contained by a substrate 932. The actuation member 912 includes a plurality of elongated posts 934, the plurality of elongated posts 934 contacting the front face of the touch sensitive device 930 and arranged in an array of lines along the length of the actuation member. The posts 934 act as force concentrators to concentrate the force from the actuation of the actuation member 912 onto the touch sensitive device 930.

A plurality of status indicators 936 are arranged in a linear array behind the actuation member 912. The status indicator is mounted on a display PCB938 (i.e., a status indicator support plate), the display PCB938 being mounted between the touch sensitive device 930 and the base 914. Fig. 19 is a perspective view showing the PCB 938. The display PCB938 includes a plurality of holes 939, and a long post 934 extends through the hole 939 into contact with the touch sensitive device 930. The actuation member 912 is preferably constructed of a translucent material such that light of the status indicators 936 is transmitted to a surface of the actuation member. A plurality of short posts 940 are disposed in the actuation member 912 directly above the status indicators 936 to act as light pipes for the linear array of status indicators. The display PCB938 includes a tab 952, the tab 952 having a connector 954 on a bottom side for connecting the display PCB938 to the main PCB 924.

The actuation member 912 includes a groove 942 that separates a lower portion 944 and an upper portion 946 of the actuation member. Upon actuation of the lower portion 944 of the actuation member 912, the dimmer 900 causes the connected lighting load to toggle from on to off (and vice versa). Preferably, a blue status indicator 948 and an orange status indicator 950 are disposed behind the lower portion 944 so that the lower portion is illuminated with blue light when the lighting load is on and illuminated with orange light when the lighting load is off. Actuation of the upper (i.e., above the recess) portion 946 of the actuation member 912 causes the intensity of the lighting load to change to a level responsive to the position of the actuation on the actuation member 912. As previously discussed for the touch dimmer 100, the status indicators 936 behind the status markers 112 are illuminated to display the intensity of the lighting load.

Fig. 20 is an enlarged partial bottom cross-sectional view of a thin touch sensitive actuator 960 according to a sixth embodiment of the present invention. The touch sensitive actuator 960 includes an actuation member 962, the actuation member 962 having two posts 964 for actuating the touch sensitive device 930. A plurality of status indicators 966 are mounted on a flexible display PCB 968 (i.e., a flexible status indicator support plate), and posts 964 of the actuation member 962 are used to actuate the touch sensitive device 930 through the flexible display PCB 968. The status indicators 966 are preferably blue LEDs and are disposed along the length of the actuation member 962. Preferably, the actuation member 962 is constructed from a translucent material such that light of the status indicators 966 is transmitted to a surface of the actuation member.

Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

1. A load control device for controlling the amount of power delivered to an electrical load from an AC power source, the load control device comprising:

a semiconductor switch for coupling in series electrical connection between the source and the load, the semiconductor switch having a control input for controlling the semiconductor switch between a non-conductive state and a conductive state;

a controller operatively coupled to the control input of the semiconductor switch for controlling the semiconductor switch between the non-conductive state and the conductive state;

a touch sensitive actuator having a touch sensitive front surface responsive to point actuations characterized by a position and a force, the touch sensitive actuator having an output operatively coupled to the controller for providing a control signal to the controller; and

a stabilization circuit coupled to the output of the touch sensitive actuator;

wherein the control signal is substantially only responsive to the position of the point actuation.

2. The load control device of claim 1, wherein the stabilization circuit comprises a capacitor.

3. The load control device of claim 2, wherein the touch sensitive actuator comprises a resistive divider to provide a DC voltage at the output, the DC voltage being indicative of the position of the point actuation, the capacitor being to stabilize the DC voltage.

4. The load control device of claim 1, wherein the control signal is representative of the position of the point actuation along a longitudinal axis of the touch sensitive actuator.

5. The load control device of claim 1, wherein the control signal is only responsive to the position of the point actuation when the magnitude of the force of the point actuation is above a predetermined level.

6. A user interface for lighting control, the user interface comprising:

a touch sensitive actuator having a touch sensitive front surface that is actuated in response to a point characterized by a force and a position along a longitudinal axis of the touch sensitive actuator, the touch sensitive actuator having an output for providing a control signal representative of the position; and

a stabilization circuit coupled to the output of the touch sensitive actuator;

wherein the control signal is responsive only to the position of the point actuation.

7. A load control device for controlling the amount of power delivered to an electrical load from an AC power source, the load control device comprising:

a touch sensitive actuator having a touch sensitive front surface responsive to point actuations characterized by a position and a force, the touch sensitive actuator having an output for providing a control signal;

a usage detection circuit operatively coupled between the output of the touch sensitive actuator and the controller for determining whether the point actuation is currently occurring; and

a stabilizing circuit operatively coupled between the output of the touch sensitive actuator and the controller for stabilizing the control signal from the output of the touch sensitive actuator;

wherein the controller is responsive to the control signal when the usage detection circuit has determined that the point actuation is currently occurring.

8. The load control device of claim 7, wherein the front face of the touch sensitive actuator is disposed in an X-Y plane defined by a Y-axis extending along a longitudinal axis of the front face and an X-axis extending substantially perpendicular to the Y-axis;

wherein the control signal is representative of the position of the point actuation along the Y-axis.

9. The load control device of claim 8, wherein the usage detection circuit is to determine whether the point actuation along the Y-axis is currently occurring.

10. The load control device of claim 9, wherein the output of the touch sensitive actuator comprises a first output connection to provide a first control signal representative of the position of the point actuation along the Y-axis.

11. The load control device of claim 8, wherein the usage detection circuit is to determine whether the point actuation along the X-axis is currently occurring.

12. The load control device of claim 11, wherein the output of the touch sensitive actuator comprises a first output connection to provide a first control signal representative of the position of the point actuation along the Y-axis and a second output connection to provide a second control signal representative of the position of the point actuation along the X-axis.

13. The load control device of claim 8, wherein the stabilization circuit comprises a capacitor coupled to the output of the touch sensitive actuator.

14. A user interface for lighting control, the user interface comprising:

a usage detection circuit operatively coupled to the output of the touch sensitive actuator for determining whether the point actuation is currently occurring;

a stabilizing circuit operatively coupled to the output of the touch sensitive actuator and comprising an output, the stabilizing circuit to stabilize the control signal from the output of the touch sensitive actuator; and

a controller coupled to the output of the usage detection circuit and the stabilization circuit, the controller being responsive to the control signal when the usage detection circuit has determined that the point actuation is currently occurring.

15. In a control circuit for operating an electrical load in response to an output signal from a touch pad, the touch pad includes an elongated manually touchable resistive area that produces an output signal at an output terminal, the signal being indicative of a position of a manual touch to the touch pad, the control circuit comprising a microprocessor having an input connected to the output signal, and generating an output for controlling the load in response to a manual input to the touch pad, the improvement comprising a filter capacitor connected between the output terminal and a ground terminal, a resistive-capacitive circuit is defined in resistance with the touch pad, the resistive-capacitive circuit characterized by a time constant and adapted to prevent large transient voltage changes due to low pressure touches of the touch pad.

16. The circuit of claim 15, wherein the touch pad is a resistive sheet connected to a fixed bias voltage and an output terminal spaced from the connecting portion of the fixed bias voltage, the output terminal being connected to the resistive sheet by an operator's touch.

17. The circuit of claim 15, wherein the contact pad is a capacitive contact pad.

18. The circuit of claim 15, wherein the time constant is in a range from about 0.0304 seconds to about 0.076 seconds.

19. The circuit of claim 18, wherein the time constant is about 0.0684 seconds.

20. The circuit of claim 15, wherein the output voltage is variable between 0 and 5 volts, and wherein the filter capacitor has a size that is fully charged in 40 milliseconds.

21. The circuit of claim 20, wherein the capacitance of the filter capacitor is about 9 microfarads.

22. The circuit of claim 15, wherein the load is a dimmable light source.

23. The circuit of claim 22, wherein the touch screen is affixed to a surface of a wall box dimmer.

24. The circuit of claim 16, wherein the touch pad is a three-wire screen for generating an output related to the location along the length of the area touching the screen.

25. The circuit of claim 16, wherein the touch pad is a four-wire screen having first and second electrodes on top and bottom, respectively, of the touch pad for producing a y output voltage to the microprocessor, and third and fourth electrodes on respective sides of the touch pad for producing an x output voltage to the microprocessor, the filter capacitor connecting the y output voltage to ground, and a resistor connecting the x output to ground; the microprocessor processes the information only if both the x and y output voltages are present.

26. The circuit of claim 18, wherein the filter capacitor has a capacitance of from 4 to 10 microfarads.

27. The circuit of claim 19, wherein the filter capacitor has a capacitance of from 4 to 10 microfarads.

28. In a manual control arrangement for generating an electrical signal in dependence on the position at which a touch screen is touched; the control structure comprises a resistive touch screen having control voltages connected to terminals at opposite ends thereof and having output terminals connected to the touch screen at locations where local manual pressure is applied to the screen by a user; a microprocessor having an input connected to said output terminal and generating an output related to said position of said screen receiving said localized manual pressure; the improvement comprises a filter capacitor connected between said output terminal and ground terminal and defining an R/C circuit with a resistance of said touch screen between said location where said screen receives local manual pressure and one of said terminals of said touch screen.

29. The structure of claim 28, wherein the output at the output terminal has an output voltage versus pressure characteristic that increases from a low voltage for a low pressure touch to a higher voltage for a high pressure touch, thereby enabling a low pressure touch to be erroneously perceived as a touch on the screen that has a high output resistance in the R/C circuit; the capacitor has a value that prevents the capacitor from being charged to an operational output level to the microprocessor by large transient voltage changes due to low pressure touches to the touch screen.

30. The structure of claim 29, wherein the touch screen is a 7600 ohm screen and the capacitor has a capacitance of about 9 microfarads.

31. The structure of claim 28, wherein said touch pad is a four-wire screen having first and second electrodes on the top and bottom, respectively, of said touch pad for producing a y output voltage to said microprocessor, and third and fourth electrodes on the respective sides of said touch pad for producing an x output voltage to said microprocessor; the filter capacitor connects the y output voltage to the ground; and a resistor connects the x output to ground; whereby the microprocessor processes information only when both the x and y output voltages are present.

32. The structure of claim 29, wherein said touch pad is a four-wire screen having first and second electrodes on the top and bottom, respectively, of said touch pad for producing a y output voltage to said microprocessor, and third and fourth electrodes on the respective sides of said touch pad for producing an x output voltage to said microprocessor; the filter capacitor connects the y output voltage to the ground; and a resistor connects the x output to ground; whereby the microprocessor processes information only when both the x and y output voltages are present.

33. The structure of claim 32, wherein said touch pad is a four-wire screen having first and second electrodes on the top and bottom, respectively, of said touch pad for producing a y output voltage to said microprocessor, and third and fourth electrodes on the respective sides of said touch pad for producing an x output voltage to said microprocessor; the filter capacitor connects the y output voltage to the ground; and a resistor connects the x output to ground; whereby the microprocessor processes information only when both the x and y output voltages are present.

34. The structure of claim 29, wherein the y output is sampled approximately 99% of the time to determine the location of the point touching the touch screen and the x output is sampled approximately 1% of the time to determine whether the touch screen is touched.

35. A process for generating an operating signal from a resistive touch screen, wherein the output voltage on an output terminal is related to both the position on the screen area touched by a user's finger and the pressure of the touch; the process includes generating an x signal in response to a touch at any location on the surface of the screen and a y signal in response to the location of the touch to the screen, and applying the x and y signals to a microprocessor; the microprocessor generates an output signal to the circuit to be controlled only when there is an x output signal at the end of a predetermined sampling interval and also a y output signal.

36. The process of claim 35, further comprising connecting the x and y signals to respective low and high value capacitors.

37. The process of claim 35, wherein the y signal is sampled for at least 99% of a measurement interval and the x signal is sampled for less than about 10% of the measurement interval.