Field of Invention:
The present invention relates to a capacitive touch based switch with illumination for automotive applications. More particularly, the present invention relates to a switch or switch bank including one or more capacitive touch based switches with illumination.
Background of the Invention:
In the automotive vehicles like passenger cars, multi utility vehicles, sports utility vehicles, commercial vehicles like trucks and buses etc, a variety of electrical switching systems as hazard, airbag, eco, front fog lamp, rear fog lamp, fuel lid opener, trunk lid opener, hood opener etc, is integrated for meeting various functions.
Control switches of such electrical system for the said vehicles are mounted over the dashboard and some of these extract high current. Switches currently available for such vehicles are typically exposed contact switches and mostly include an actuator and attached plated or without plated copper contacts that may be directly actuated into and out of physical contacts with corresponding contacts of the driver circuit. Stroke of the actuator causes the actuator contact to be displaced into contact with the driver circuit contact located within the housing.
Electrical contact between the lever contact and the driver circuit contact results in a closed circuit for actuating the desired function of the particular electrical system of the vehicle. The said switches also have a source of illumination like led or bulb for showing the function on or off
In addition, physical contact between the actuator or moving contact and circuit or fixed contact is required to close the circuit and the contacts are exposed to the environment which results in high failure of function owing to frictional contact wearing, oxidation or corrosion building up at the contact points between the actuator contact and the circuit contact results in impedance of the switch and reduce the switch life, ultimately. Moreover, the said traditional switches consist of high cost of manufacturing due to

convoluted design of fixed and moving contacts meeting high current rating requirements.
Objects of the Invention:
The main object of the present invention is to provide a capacitive touch based switch with illumination. Another object of the present invention is to provide a switch bank including plurality of touch based switches with illumination.
Summary of Invention:
Accordingly, the present invention provides an illuminated capacitive touch switch comprising:
• a non-conductive cover including touch-sensitive area adapted to be touched by a user and a portion requiring illumination located within the said touch sensitive area;
• capacitive electrode provided on a surface of a touch based printed circuit board, the capacitive electrode interposed between the non-conductive cover and the touch based printed circuit board;
• light source located beneath the touch based printed circuit board; and
• aperture formed in the printed circuit board such that the light generated by the said light source traverses through the aperture and illuminates said area requiring illumination of the non-conductive cover.
In an embodiment of the present invention, a surface area of the light source emitting the light is lesser than a surface area of the portion requiring illumination.
In another embodiment of the present invention, the aperture is formed so as to fall wholly within an area defined by the capacitive electrode provided on the surface of the touch based printed circuit board.
In yet another embodiment of the present invention, shape and size of the aperture is such that the light generated by the said light source illuminates said portion requiring illumination of the non-conductive cover.
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In still another embodiment of the present invention, the light source is located on the touch based printed circuit board on a surface opposite to the surface carrying the capacitive electrode.
In a further embodiment of the present invention, the aperture is provided with a tapering such that a diameter of the aperture on the surface carrying the light source is less than or equal to a size of the light source, the diameter of the aperture on the surface carrying the light source is less than a diameter of the aperture on the surface having the capacitive electrode.
In a furthermore embodiment of the present invention, the light source is located on a printed circuit board distinct from the touch based printed circuit board carrying the capacitive electrode.
In one more embodiment of the present invention, if the light source is located on a printed circuit board distinct from the touch based printed circuit board carrying the capacitive electrode, a diameter of the aperture on the touch PCB is equal to or greater than surface area of the portion requiring illumination.
In an embodiment of the present invention, in response to a touch, the capacitive electrode provided on a surface of a printed circuit board is configured to produce a capacitance change, detectable as an ON signal and an OFF signal.
In another embodiment of the present invention, the switch further comprises a micro-controller configured to receive the ON/OFF signal from the capacitive electrode as input signal and provide an output signal to an electrical device coupled to the micro-controller through a driver circuit; said micro-controller being further configured to control flow of power to the light source upon receiving input signal from the capacitive electrode.
In yet another embodiment of the present invention, the light source is a surface mounted LED (SM-LED), and preferably a bi-colour SM-LED for indicating the ‘ON’ and ‘OFF’ position of the switch element by different colors.
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In still embodiment of the present invention, the micro-controller is configured to control the flow of power to the LED for indicating the ‘ON’ and ‘OFF’ position of the switch element by different intensity of the illumination.
In a further embodiment of the present invention, the micro-controller is configured to flash illuminated symbol w.r.t. switch application requirement.
The present invention also provides an illuminated capacitive touch based switch bank
comprising:
a non-conductive cover including plurality of touch-sensitive areas adapted to be touched
by a user and portions requiring illumination located within the corresponding touch
sensitive area;
capacitive electrodes provided on a surface of a printed circuit board, the capacitive
electrode interposed between the non-conductive cover and the printed circuit board;
light sources located beneath the printed circuit board;
apertures formed in the printed circuit board such that the light generated by the said light
sources traverses through the apertures and illuminate said areas requiring illumination of
the non-conductive cover; and
at least one micro-controller configured to receive input from each of the capacitive
electrodes and being configured to provide output signal to one or more electrical device
coupled to the micro-controller through driver circuit to suitably active or deactivate the
electrical device.
Brief Description of Drawings:
The drawings diagrammatically illustrate by way of example, not by way of limitation, one form or mechanism for carrying out one method of the invention, wherein:
Figure 1 & Figure 2 illustrates isometric top-side & bottom-side view of a capacitive touch based switch with illumination according to an embodiment of the present invention.
Figure 3 shows top view of a capacitive touch based switch with illumination according to an embodiment of the present invention.
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Figure 4 illustrates the area allocated for touch, for symbol illumination and for function illumination on the non-conductive cover according to an embodiment of the present invention.
Figure 5 illustrates the problem faced of not being able to illuminate the entire area allocated for illumination.
Figure 6 illustrates the problem faced (lack of land for mounting/soldering led on touch PCB) when the hole diameter in the touch PCB is increased so as to illuminate complete required area (i.e. symbol illumination area).
Figure 7 illustrates the capacitive touch based illuminated switch developed in accordance with the present invention wherein a leaded LED (LEDs with longer legs) is mounted on to a back face of touch PCB which has hole having a diameter substantially equal to the symbol illumination area.
Figure 8a & Figure 8b illustrate the capacitive touch based illuminated switch developed in accordance with the present invention wherein a surface mountable LED (SM-LED) is mounted onto a back face of touch PCB, wherein the touch based PCB is developed with required taper at hole upper edge.
Figure 9 illustrates top view of the capacitive touch based illuminated switch developed in accordance with the present invention which use of a secondary PCB having mounted thereupon surface mountable LED (SM-LED) onto a front face (which faces touch PCB).
Figure 10 illustrates bottom view of the capacitive touch based illuminated switch of figure 9.
Figure 11 illustrates the illumination attained on the non-conductive cover which is equal to or greater than the area allocated for symbol illumination after implementing the method shown in figures 8 and/or 9.
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Figure 12 illustrates front view of top PCB of a capacitive touch based switch with illumination according to an embodiment of the present invention.
Figure 13 shows exploded view of a capacitive touch based switch with illumination according to an embodiment of the present invention.
Figure 14, Figure 15, Figure 16 and Figure 17 illustrate the block diagrams of the circuit of the capacitive touch based switch with illumination according to an embodiment of the present invention.
Description of the present invention:
The present invention is further described here-below by way of illustration and more particularly, the following paragraphs are provided in order to describe the best mode of working the invention and nothing in this section should be taken as a limitation of the claims (which will be inserted subsequently).
Before describing in detail various embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in the combination of the various elements in the manner described in the claims. Accordingly, the drawings show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein. The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that an apparatus that comprises a list of parts / devices does not include only those parts / devices but may include other parts or devices not expressly listed or inherent to such apparatus. An element proceeded by “comprises… a” does not, without more constraints, preclude the existence of additional elements.
Accordingly, the present invention provides a capacitive touch based switch with illumination which overcomes at least one of the problems associated with the prior existing switches. The present invention also provides a switch bank which includes plurality of capacitive touch based switches with illumination. The present invention
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relates to a capacitive touch based switches with illumination comprising at least a touch sensitive switch and a micro controller.
A touch sensitive switch which is a switch that is implemented as a trace on a printed circuit board, is operative to produce “ON” and “OFF” signal. The architecture of the trace creates a capacitive element. Touching this trace with a finger creates a change in capacitance, which is detectable using a variety of techniques. The micro controller present in the capacitive touch based switches with illumination is configured to receive the signal from the trace on a printed circuit board as input signal and provide an output signal to an electrical device coupled to the micro controller through a driver circuit. The switch element also comprises a light emitting diode (LED) and has a transparent portion that receives illumination from the LED. The micro controller is configured to control flow of power to the LED upon receiving input signal from the switch element.
The present invention also relates to a capacitive touch based switch or switch bank with illumination comprising plurality of switch elements and at least one micro controller. Each of the plurality of switch element comprises LED and has a transparent portion that receives illumination from the LED. The micro-controller is also configured to control flow of power to the LED upon receiving input signal from the switch element.
Moreover, present invention also relates to a capacitive touch based switch or switch bank with illumination wherein the switch element comprising as a trace on a printed circuit board. The architecture of the trace creates a capacitive element. Touching this trace with a human’s finger creates a change in capacitance, which is detectable using a variety of techniques. Capacitive touch based switch or switch bank with illumination can be as simple as a trace on a PCB that forms one plate of a capacitor and an object that is in close proximity to the pad represents the other plate. With respect to human interface it is often a human’s finger that becomes the second plate of the capacitor. As the distance between the finger and the pad decreases, the capacitance increases inversely with the distance.
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Furthermore, present invention also relates to a capacitive touch based switch or switch bank with illumination wherein the transparent portion comprises at least one symbol which is disposed on the touch knob.
In addition, present invention also relates to a capacitive touch based switch or switch bank with illumination wherein the micro-controller is configured to control the flow of power to the LED for indicating the ‘ON’ and ‘OFF’ position of the switch function by different intensity of the illumination.
Additionally, present invention also relates to a capacitive touch based switch or switch bank with illumination wherein the micro-controller is configured to flash the illuminated symbol w.r.t. switch application requirement.
Now with reference to the drawings shown in Figure-1 to Figure-17, the fabrication of the capacitive touch based switch with illumination in accordance with the concept of present invention, the methodology of implementation and scope of the present invention are now described in detail.
Figure 1 & Figure 2 illustrates isometric top-side & bottom-side view of a capacitive touch based switch with illumination according to an embodiment of the present invention. Figure 3 illustrates the top view of switch bank which has plurality of switches that can be used for various automotive applications according to an embodiment of the present invention. The diagram illustrates various switches that may be comprised in the switch bank. The switches present can be used for controlling the functions as hazard warning, front fog lamp, rear fog lamp, fuel lid opener, heated rear window, air bag, eco etc. in automotive vehicles. All the switches present in the switch bank have symbols on them. The symbols identify the respective control function performed by the switches.
Figure 4 illustrates that in the top non-conductive cover a touch area, an area for symbol illumination and an area for illumination with function are provided. It can be noted that the area for symbol illumination is allocated within the touch area. The touch area is defined as the area beneath which a corresponding electrode is located and upon touching
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of which, a corresponding switching function (OFF to ON or ON to OFF) has to be performed by the processor forming part of the switch.
According to the teachings of the present invention, the capacitive touch based illuminated switch comprises:
• a non-conductive cover including touch-sensitive area adapted to be touched by a user and a portion requiring illumination located within the said touch sensitive area;
• capacitive electrode provided on a surface of a touch based printed circuit board, the capacitive electrode interposed between the non-conductive cover and the touch based printed circuit board;
• light source located beneath the touch based printed circuit board; and
• aperture formed in the printed circuit board such that the light generated by the said light source traverses through the aperture and illuminates said area requiring illumination of the non-conductive cover.
One of the major challenges faced in the capacitive touch based illuminated switch is the ability to illuminate the entire symbol illumination area or the entire function illumination area. As illustrated in figure 5, it has been found that the light source generally illuminates only a part of the symbol illumination area or the function illumination area. Thus, to address the aforesaid problem US Patent No. 7,923,654, the teachings of which herein incorporated as reference, provides a planar light guide. However, the Applicants have found that such a mechanism is not cost effective. Thus, the Applicants have tried various other mechanism for attaining illumination of the symbol illumination area or the function illumination area.
By way of example, and as illustrated in figure 6, the Applicants have tried to enlarge the size of the diameter of the aperture provided in the touch based PCB (from X to a larger value), but have found that if the diameter size is increased, the space available for holding of the LED decreases and it is no more possible to effectively mount the LED.
In yet another attempt, as illustrated in figure 7, the Applicants have tried to enlarge the size of the diameter of the aperture provided in the touch based PCB and mount a leaded
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LED i.e. a LED having longer legs. However, LEDS with longer legs can be broken in vibrations/ mechanical jerks etc as well as there are chances of axis misalignment. Thus, this option of addressing the problem is not found to be ideal.
Although not illustrated, attempts were made to make the touch knob itself act as a light spreading medium i.e. entire knob acts as a light guide itself. However, these attempts also did not provide a commercially viable solution.
In yet another attempt which was similar to the construction described and illustrated in figure 7, instead of leaded LED, a special chip LED holder with good strength was tried. However, even this attempt did not provide good working product and furthermore, the cost of manufacturing was very high.
Coming to figure 8a & figure 8b, a capacitive touch based illuminated switch developed in accordance with the present invention wherein a surface mountable LED (SM-LED) is mounted onto a back face of touch PCB and wherein the touch based PCB is developed with required taper at hole upper edge. In this construction, a surface area of the light source emitting the light is lesser than a surface area of the portion requiring illumination. The aperture which allows the light to pass through is formed so as to fall wholly within an area defined by the capacitive electrode provided on the surface of the touch based printed circuit board and the shape and size of the aperture is such that the light generated by the said light source illuminates said portion requiring illumination of the non-conductive cover. The light source which is SM-LED is located on the touch based printed circuit board on a surface opposite to the surface carrying the capacitive electrode and the aperture is provided with a tapering such that a diameter of the aperture on the surface carrying the light source is less than or equal to a size of the light source, the diameter of the aperture on the surface carrying the light source is less than a diameter of the aperture on the surface having the capacitive electrode.
Coming to figure 9 and 10, a capacitive touch based illuminated switch developed in accordance with the present invention wherein a surface mountable LED (SM-LED) is mounted onto a printed circuit board distinct from the touch based printed circuit board
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carrying the capacitive electrode. In this case, a diameter of the aperture on the touch PCB is made equal to or greater than surface area of the portion requiring illumination. The gap (or height) between the touch based PCB and the secondary PCB is such that the light emitted by the SM-LED is diverges and covering the entire symbol illumination area or the function illumination area (as the case may be).
The Applicants have found that by adopting the construction as illustrated in any of figures 8 to 10, it is now possible to cost effectively and sufficiently illuminate the entire symbol illumination area or the entire function illumination area (as the case may be) and the same has been illustrated in figure 11.
Referring to figure 12 is exemplary illustration of top view of touch PCB according to an embodiment of the present invention. The figure further illustrates the design of touch pad over the said PCB as per requirement of the various said functional requirement of the vehicle.
Figure 13 shows an exploded view of a capacitive touch based switch with illumination in accordance of an embodiment. The touch knob which is of non conducting transparent injection molding material, is having black painted in order to perform laser etching of symbols as shown in figure-3, to pass away the illumination as per specific shape for functional indication. Touch PCB is having touch pads as shown in figure 12, for getting input signal from the user’s finger. The said touch PCB is having through holes as illustrated in figure 8 for passing away the illumination from the surface mounted LEDs mounted over the back side of the said touch PCB. The said top pcb and the back face of the said switch knob have been joined together resulting in a touch pcb sub assembly with a both side adhesive tape or with any other adhesion means, in such a manner that there is not any slight air gap between the both. The said touch pcb sub assembly is assembled with the housing through mechanical snaps locks provided in the said housing and the said switch knob. An ECU PCB (additional PCB) which is been mounted with at least one microcontroller and other electronic components, has been provided with the slots for soldering with the terminals from the connectors in the back cover. The said back cover is designed in such a manner that at least one male connector is integral part
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of it as shown in figure in order to save very expensive readymade connectors and the said back cover is assembled with the said housing by screws as shown in figure. Instead of mounting the SM-LED in the back side of the touch PCB, it is possible as described in the embodiment with respect to figures 9 and 10, the SM-LED can be mounted on to the ECU-PCB and in which case, the space between the touch PCB and the ECU-PCB and the size of the aperture in the touch PCB can be appropriately adjusted to attain the overall objective of sufficiently illuminating the entire symbol illumination area or the entire function illumination area.
By way of example, and as illustrated in figure 14, figure 15, figure 16 and figure 17 (which are the illustrated block diagrams of the circuit of the capacitive touch based switch banks with illumination) comprising high side drivers for airbag & eco function and relays for airbag & eco function respectively in accordance of an embodiment. The capacitive touch based switch with illumination as described in the present invention is a low current type switch bank & its function based on capacitive touch technology. Output signal of said top PCB pad goes to micro-controller & driver IC, which in turn actuate the related load. Other output signals from the micro-controller control the flow of power to the various LED’s present in various switches.
Advantages of the Present Invention:
1. In the major advantage, switching feel of capacitive touch based switch is luxurious touch feeling as compared to operative feel of conventional switches involving movement of knob to a certain distance for making or breaking contact.
2. Another major advantage, switching time of capacitive touch based switch is in fraction of second and lesser as compared to the time required to operate conventional switches involving forward and backward stroke of knob to a certain distance for making or breaking contact.
3. In yet another major advantage, the aesthetic look of the capacitive switch bank is much better as compared to the conventional switch bank owing to the fact that the knob for all the switches in capacitive switch bank is single and uniform while there are separate knobs for each switch in the conventional switch bank and
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when the said separate knob moves forward and backward, height difference appears with respect to another fixed separate knobs.
4. Moreover, capacitive switch life is much more than conventional switches as no physical contact in switching mechanism and switch function is based on capacitive touch technology.
5. Furthermore, capacitive switch is more economic than conventional switches due to lesser number parts.
6. The symbol illumination achieved by means of capacitive touch mechanism is unique.
7. The capacitive switch withstands much more endurance or durability cycles as compared to conventional contact type switches.
8. The capacitive switch performs the requirements of environmental and mechanical conditions like dust proof, thermal resistance, cold resistance, thermal shocks, vibration resistance etc.
The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.

WE CLAIM:
1. An illuminated capacitive touch based switch comprising:
• a non-conductive cover including touch-sensitive area adapted to be touched by a user and a portion requiring illumination located within the said touch sensitive area;
• capacitive electrode provided on a surface of a printed circuit board, the capacitive electrode interposed between the non-conductive cover and the printed circuit board;
• light source located beneath the printed circuit board; and
• aperture formed in the printed circuit board such that the light generated by the said light source traverses through the aperture and illuminates said area requiring illumination of the non-conductive cover.

2. The illuminated capacitive touch based switch as claimed in claim 1, wherein a surface area of the light source emitting the light is lesser than a surface area of the portion requiring illumination.
3. The illuminated capacitive touch based switch as claimed in claim 1, wherein the aperture is formed so as to fall wholly within an area defined by the capacitive electrode provided on the surface of a printed circuit board.
4. The illuminated capacitive touch based switch as claimed in claim 1, wherein shape and size of the aperture is such that the light generated by the said light source illuminates said portion requiring illumination of the non-conductive cover.
5. The illuminated capacitive touch based switch as claimed in claim 1, wherein the light source is located on the printed circuit board on a surface opposite to the surface carrying the capacitive electrode.
6. The illuminated capacitive touch based switch as claimed in claim 5, wherein the aperture is provided with a tapering such that a diameter of the aperture on the
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surface carrying the light source is less than or equal to a size of the light source, the diameter of the aperture on the surface carrying the light source is less than a diameter of the aperture on the surface having the capacitive electrode.
7. The illuminated capacitive touch based switch as claimed in claim 1, wherein the light source is located on a printed circuit board distinct from the printed circuit board carrying the capacitive electrode.
8. The illuminated capacitive touch based switch as claimed in claim 7, wherein a diameter of the aperture is equal to or greater than surface area of the portion requiring illumination.
9. The illuminated capacitive touch based switch as claimed in claim 1, wherein in response to a touch, the capacitive electrode provided on a surface of a printed circuit board is configured to produce a capacitance change, detectable as an ON signal and an OFF signal.
10. The illuminated capacitive touch based switch as claimed in any of the previous claims, further comprising a micro-controller configured to receive the ON/OFF signal from the capacitive electrode as input signal and provide an output signal to an electrical device coupled to the micro-controller through a driver circuit; said micro-controller being further configured to control flow of power to the light source upon receiving input signal from the capacitive electrode.
11. The illuminated capacitive touch based switch as claimed in any of the previous claims, wherein the light source is a surface mounted LED (SM-LED), and preferably a bi-colour SM-LED for indicating the ‘ON’ and ‘OFF’ position of the switch element by different colors.
12. The illuminated capacitive touch based switch as claimed in any of the previous claims, wherein the micro-controller is configured to control the flow of power to the LED for indicating the ‘ON’ and ‘OFF’ position of the switch element by different intensity of the illumination.
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13. The illuminated capacitive touch based switch as claimed in any of the previous claims, wherein the micro-controller is configured to flash illuminated symbol w.r.t. switch application requirement.
14. An illuminated capacitive touch based switch bank comprising:
a non-conductive cover including plurality of touch-sensitive areas adapted to be touched by a user and portions requiring illumination located within the corresponding touch sensitive area;
capacitive electrodes provided on a surface of a printed circuit board, the capacitive electrode interposed between the non-conductive cover and the printed circuit board;
light sources located beneath the printed circuit board;
apertures formed in the printed circuit board such that the light generated by the said light sources traverses through the apertures and illuminate said areas requiring illumination of the non-conductive cover; and
at least one micro-controller configured to receive input from each of the capacitive electrodes and being configured to provide output signal to one or more electrical device coupled to the micro-controller through driver circuit to suitably active or deactivate the electrical device.
15. An illuminated capacitive touch based switch and an illuminated capacitive touch
based switch bank substantially herein described with reference to the
accompanying drawings.