Abstract:
A plurality of color LEDs are commonly coupled to a source of operating supply. A plurality of switching transistors and current limiting resistors in series therewith are coupled to the color LEDs to control the current there through in response to switching transistor conduction. A microcontroller having an input signal and a plurality of outputs configured in response thereto is operatively coupled to the plurality of switching transistors to control the conduction and thereby illumination output of the color LEDs to achieve incremental color blending.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to illumination systems and particularly to those utilized in products such as toys, games or the like. 
   BACKGROUND OF THE INVENTION 
   The development of light emitting diodes (LEDs) has provided a dramatic improvement in the availability of low-cost, efficient illumination sources. Such low-cost illumination sources have made possible which would otherwise be significantly larger of substantially increased in cost and power consumption. The power required to provide illumination using LEDs is dramatically reduced from that provided by other typical illumination devices such as incandescent lights or the like. 
   In addition to their advantages of lower cost and lower power requirements, LEDs also enjoy substantial advantages in their rapid response in transitioning between on and off states. Unlike incandescent lamps or the like which have a relatively slow transition time between illumination and non-illumination, LEDs are substantially more rapid in transition then can be perceived by the human eye. Thus, LEDs appear to the observer to be instantly switched on or off. 
   A still further advantage found in LEDs is their compatibility with digital electronic control circuits. One of the more interesting applications of LEDs as illumination devices is found in the art generally referred to as “color blending”. This art derives its general name from the capability of differently colored light emitting diodes being used to provide resulting colors which are combinations or “blends” of the individual LEDs in the group. Perhaps the common form of color blending using LEDs arises in systems which utilize one or more LEDs of each of the three primary colors, red, blue and green. In this use, another advantage of LEDs is evident in that the typical small size of LEDs allows their close positioning to enhance the color blending phenomenon. A simple color blending system may utilize three LEDs one of each primary color (red, blue and green) formed in a closely spaced arrangement. As the proportions of each color LED output are varied, the resulting blended color of illumination may be carefully controlled. In higher power arrays pluralities of each LED color output may be grouped or arranged as needed and controlled in a similar fashion. 
   Not surprisingly, the extended development and improvement of LEDs has motivated practitioners in the art to utilize such color blending LED illumination systems in a variety of devices. For example, U.S. Pat. No. 6,016,038 and its parent U.S. Pat. No. 6,150,774 both issued to Mueller et al. and both entitled MULTICOLORED LED LIGHTING METHOD AND APPARATUS in which an array of LEDs is controlled by a processor to alter the brightness and/or color of the generated light. Example is given utilizing pulse-width modulated signals. The resulting illumination may be controlled by a computer program to provide complex, pre-designed patterns of light in virtually any environment. 
   U.S. Pat. No. 6,095,661 issued to Lebens et al. sets forth a METHOD AND APPARATUS FOR AN LED FLASHLIGHT in which an elongated flashlight body supports a power supply and controller together with an on/off switch. The illumination head of the flashlight supports a plurality of LEDs operatively coupled to the controller. In one embodiment, differently colored LEDs are selectively powered in groups to provide a light output color using color blending. 
   U.S. Pat. No. 5,947,789 issued to Chan sets forth a TOY SWORD HAVING A VARIABLE COLOR ILLUMINATED BLADE featuring a handle section and a translucent blade section. The handle section houses a light source for illuminating an interior of the blade section. A switch energizes the light source and a multicolored filter is disposed between the light source and the translucent blade selection to provide color selection illumination of the blade section. 
   U.S. Pat. No. 6,190,229 issued to Nadel et al. sets forth a FIBER OPTIC ENHANCED FIGURINE ASSEMBLY generally resembling a horse having a quantity of fiber optic hair disposed as the main and tail of the horse. A power source within the body of the horse energizes a plurality of LEDs which illuminate the fiber optic bundles. 
   U.S. Pat. No. 6,431,937 issued to Lau et al. sets forth a TOY SYSTEM having a baton-like signal transmitter and a doll which includes an inferred signal receiver for receiving inferred signals from the transmitter. The doll produces sound such as songs or the like in response to signals received by the signal transmitter. 
   U.S. Pat. No. 3,654,710 issued to Barnard sets forth a SELECTIVELY ILLUMINATABLE TOY having a housing supporting a plurality of switches, a battery power source and a plurality of illuminatable lights. 
   U.S. Pat. No. 5,854,542 issued to Forbes sets forth FLASHING AND DIMMING FLUORESCENT LAMPS FOR A GAMING DEVICE operated continuously during normal operation and then flashed to signal promotional operation. Alternatively, an illumination lamp may be dimmed during normal operation and then operated at full brightness during promotional activities. 
   U.S. Pat. No. 4,305,223 issued to Ho sets forth a MAGIC EYEBALL having a plurality of LEDs, a power apparatus for supplying electrical power to said LEDs and a plurality of switches which are placed under suitable parts of a toy body. By means of the touch activation of the switches the LEDs are able to emit a changeable light. 
   U.S. Pat. No. 4,363,081 issued to Wilbur sets forth ILLUMINATED GREETING CARDS having a first portion formed of sheet stock as a display panel defining one or more apertures. LEDs are disposed behind the display panel to provide illumination through the apertures. A printed circuit board controls the LEDs and the light produced thereby. 
   A number of additional devices utilizing some form of selective illumination is provided in additional patents such as U.S. Pat. No. 4,373,722 issued to Kite et al., U.S. Pat. No. 4,338,742 issued to Outtrim et al., U.S. Pat. No. 4,282,680 issued to Zaruba, U.S. Pat. No. 4,600,974 issued to Lew et al., U.S. Pat. No. 4,820,229 issued to Spraggins, U.S. Pat. No. 4,874,343 issued to Rosenthal, U.S. Pat. No. 4,915,666 issued to Maleyko, U.S. Pat. No. 4,971,592 issued to Carcia, III. and U.S. Pat. No. 4,991,066 issued to McCowan. 
   Still further examples of illuminated apparatus generally related to the present invention is found in the following U.S. Pat. Nos. 5,054,778; 5,118,319; 5,139,455; 5,269,719; 5,316,293; 5,375,044; 5,575,554; 5,743,796 and 6,371,638. 
   Despite the substantial development of lighting devices and particularly the substantial development of illumination systems using LEDs, there remains nonetheless a continuing need in the art for more low-cost, effective and efficient LED color blending systems which are particularly well suited to use in lower cost toys and game products. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is general object of the present invention to provide an improved lower cost and efficient color blending illumination systems suitable for use with LEDs. It is a more particular object of the present invention to provide an improved color-blending illumination system using LEDs which is particularly well suited to effective coupling to digital electronic devices. 
   In accordance with the present invention there is provided an incremental color-blending illumination system comprising: a plurality of color LEDs each having a first electrode coupled to a source of operation supply and a second electrode; a plurality of transistor switches; a plurality of resistors coupling the transistor switches to the second electrodes; and a microcontroller having a plurality of outputs coupled to the plurality of switching transistors, the micro controlled providing incremental color blending of light produced by the color LEDs by selectively activating one or more of the switching transistors. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements and in which: 
       FIG. 1  sets forth a schematic diagram of an incremental color-blending illumination system constructed in accordance with the present invention having three transistor switches and three color LEDs; 
       FIG. 2  sets forth a schematic diagram of an incremental color-blending illumination system constructed in accordance with the present invention having three color LEDs and six transistor switches symmetrically distributed among the color LEDs; 
       FIG. 3  sets forth a schematic diagram of an incremental color-blending illumination system constructed in accordance with the present invention having three color LEDs and six transistor switches distributed in a non-symmetrical manner between the LEDs. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  sets forth an incremental color-blending illumination system constructed in accordance with the present invention and generally referenced by numeral  10 . System  10  includes a microcontroller  11  having an input  12  and three output terminals  13 ,  14  and  15 . System  10  further includes a plurality of switching transistors  30 ,  31  and  32  each having their respective emitters connected to ground and their respective bases coupled to outputs  13 ,  14  and  15  of microcontroller  11 . A trio of color LEDs  20 ,  21  and  22  are each capable of producing red, green and blue light respectively when energized. LEDs  20 ,  21  and  22  have their respective anodes commonly coupled to a source of operating supply voltage  16 . LED  20  is coupled to the collector of transistor  30  by a current limiting resistor  25 . Similarly, the cathodes of LEDs  21  and  22  are coupled to the collectors of transistors  31  and  32  by current limiting resistors  26  and  27  respectively. 
   The fundamental system shown in  FIG. 1 , and referenced as system  10 , is a basic symmetrical system in that each color LED is controlled by a single current limiting resistor and switching transistor. As a result, the light produced by LEDs  20 ,  21  and  22  is determined by the switching states of transistors  30 ,  31  and  32 . For example, if transistor  30  is turned on or conductive, resistor  25  is effectively coupled to ground and LED  20  is energized. The light output of LED  20  for a given positive voltage  16  is determined by the characteristics of LED  20  and the resistance of resistor  25 . Similarly, conduction by transistor  31  couples resistor  26  to ground and causes a current flow through LED  21 . Finally, conduction of transistor  32  couples resistor  27  to ground and causes conduction of LED  22 . The combined light output both in color and illumination is determined by the light outputs of LEDs  20 ,  21  and  22 . Since each LED produces a different color light, the blended light output of LEDs  20 ,  21  and  22  is controlled by the output signals of microcontroller  11  applied to the basis of switching transistors  30 ,  31  and  32 . Thus, if output  13  is high, transistor  30  conducts and LED  20  is activated. Similarly, if output  14  is high, transistor  31  is conductive and LED  21  produces light output. Finally, if output  15  is high, transistor  32  is conductive and LED  22  produces light output. 
   Accordingly, with three output terminals applied to three switching transistor controlling three light emitting diodes, a total combination of seven colors of blended light output from LEDs  20 ,  21  and  22  is provided. The relative conduction levels of each of diodes  20 ,  21  and  22  is established primarily by the relative resistances provided by resistors  25 ,  26  and  27  in relation to the operating characteristics of diodes  20 ,  21  and  22 . 
   System  10  is therefore capable of responding to an input signal at input  12  of microcontroller  11  to provide a combination of output signals at outputs  13 ,  14  and  15  to selectively or, in combination energize one or more color LEDs  20 ,  21  and  22  to provide incremental color blending of the combined light output. As mentioned above, the system shown in FIG.  1  and generally referenced by numeral  10  is a basic symmetrical circuit in that three color LEDs are controlled by three current limiting resistors in combination with three switching transistors. It will be apparent to those skilled in the art however that the present invention incremental color-blending illumination system is not limited to this symmetrical arrangement.  FIGS. 2 and 3  set forth below show examples of systems which are capable of substantially greater numbers of color blending increments. By way of overview, the system shown in  FIG. 2  provides a greater number of color blending increments while maintaining a basically symmetrical environment. In contrast, the system shown in  FIG. 3  provides additional color blending increments utilizing a non-symmetrical system. 
     FIG. 2  sets forth a schematic diagram of an incremental color-blending illumination system constructed in accordance with the present invention and generally referenced by numeral  40 . Illumination system  40  includes a microcontroller  41  having an input  42  and a plurality of outputs  43 ,  44 ,  45 ,  46 ,  47  and  48 . System  40  further includes a trio of color LEDs  50 ,  51  and  52  having their respective anodes commonly coupled to a source of operating supply voltage  49 . System  40  further includes a plurality of switching transistors  70 ,  71 ,  72 ,  73 ,  74  and  75  each having their respective emitter electrodes grounded and each having their respective base electrodes coupled to outputs  43  through  48  respectively. A current limiting resistor  55  is coupled between the collector of transistor  70  and the cathode of LED  50 . A current limiting resistor  56  is coupled between the cathode of LED  50  and the collector of transistor  71 . A current limiting resistor  57  is coupled between the cathode of LED  51  and the collector of transistor  72 . A current limiting resistor  58  is coupled between the cathode of LED  51  and the collector of transistor  73 . Finally, a current limiting resistor  59  is coupled between the cathode of LED  52  and the collector of transistor  74  while a current limiting resistor  60  is coupled between the cathode of LED  52  and the collector of transistor  75 . 
   In operation, outputs  43  through  48  are configured by microcontroller  41  in response to an input signal at input  42 . Microcontroller  41  may be fabricated in accordance with conventional fabrication techniques in which the respective output signals at outputs  43  through  48  are given either high or low voltage conditions in various combinations depending upon the input signal at input  42 . The conduction level and therefore output illumination of LED  50  is established at a first conduction level by switching transistor  70  to a conducting state and allowing current to flow through resistor  55 . The conduction level of LED  50  is further modified by switching transistor  71  to a conducting state and allowing current to flow through resistor  56 . A third conduction level for LED  50  may be established by simultaneously switching transistors  70  and  71  to conducting states causing current to flow through the parallel combination of resistors  55  and  56 . The conduction of transistors  70  and  71  is controlled by the output state of microcontroller  41  at outputs  43  and  44 . In a similar fashion, the conduction level and therefore illumination output of LED  51  is controlled by transistors  72  and  73  which in turn are controlled by outputs  45  and  46  of microcontroller  41 . Accordingly, a first light output is established by switching transistor  72  on and effectively coupling resistor  57  to ground while an alternative light output is established for LED  51  by turning transistor  73  on an effectively coupling resistor  58  to ground. Once again, a further light output condition is established for LED  51  by simultaneously switching transistors  72  and  73  to their on states causing a combined current to flow through resistors  57  and  58  which further changes the light output of LED  51 . Finally, the conduction level and therefore light output of LED  52  is established at a first condition by switching transistor  74  to a conducting state or alternatively, at a second condition by switching transistor  75  to a conducting state or a third condition by simultaneously switching transistor  74  and  75  to their on states. 
   It will be apparent to those skilled in the art that the use of six output terminals controlling the switching conditions of six switching transistors and six current limiting resistors coupled in pairs to three LEDs provides a total capability for incremental color blending which yields a total of sixty different color combinations. Thus, in response to an input signal at input  42  of microcontroller  41 , the appropriate output states for outputs  43  through  48  may be established to cause LEDs  50 ,  51  and  52  to provide relative conductions which generate any one of sixty available color blending combinations. The color blending is now more finally incremented in comparison to the circuit of FIG.  1 . However, the basic operation remains the same. 
     FIG. 3  sets forth a non-symmetrical embodiment of the present invention incremental color-blending illumination system generally referenced by numeral  80 . Illumination system  80  includes a microcontroller  81  having an input  82  and a plurality of outputs  83  through  88 . System  80  further includes a trio of color LEDs  90 ,  91  and  92  having their respective anodes commonly coupled to a source of operating supply voltage  93 . A transistor  110  has its base coupled to output  83 , its emitter coupled to ground and its collector coupled to the cathode of LED  90  by a current limiting resistor  100 . A pair of transistors  111  and  112  have their respective emitters grounded and their respective basis coupled to outputs  84  and  85  of microcontroller  81 . Transistors  111  and  112  have their respective collectors coupled to the cathode of color LED  91  by a pair of current limiting resistors  101  and  102 . A trio of switching transistors  113 ,  114  and  115  has their respective emitters grounded and their respective bases coupled to outputs  86 ,  87  and  88 . The collectors of transistors  1   13 ,  114  and  1   15  are coupled to the cathode of color LED  92  by current limiting resistors  103 ,  104  and  105  respectively. In operation, illumination system  80  is similar in function to the above-described symmetrical systems in that the conduction levels and therefore light outputs of color LEDs  90 ,  91  and  92  are controlled by switching transistors and current limiting resistors. The difference in illumination system  80  is the non-symmetrical transistor and current limiting resistor couplings to the color LEDs. Thus, the conduction level and therefore illumination output of color LED  90  is controlled entirely by resistor  100  and the switching of transistor  1   10 . In contrast, the conduction and therefore illumination output of color LED  91  is established by either or both of transistors  111  and  1   12  conduction. A first conduction level is established by turning transistor  111  on while a second conduction level is established by turning transistor  1   12  on and a third conduction level is established by turning transistors  111  and  112  on simultaneously. Thus, in illumination system  80 , color LED  91  is capable of three different illumination output levels in response to the operating conditions of transistors  111  and  112 . By way of comparison, it is noted that the illumination output of color LED  90  is capable of a single illumination level determined by the operative condition of transistor  110 . In a similar fashion, the conduction and therefore illumination output of color LED  92  is determined by the operating conditions of transistors  113 ,  114  and  115 . With transistor  113  conducting, a first illumination level is established for color LED  92  by conduction through resistor  103 . A second conduction level is established by turning on transistor  114  and the conduction through  104 . A third conduction level is established by turning on transistor  115  and the conduction of resistor  105 . A fourth conduction level is established by simultaneously turning on transistors  113  and  114  placing resistors  103  and  104  in parallel. A fifth operating condition is established by simultaneously turning on transistors  113  and  115  placing resistors  103  and  105  in parallel and finally a sixth condition is established by simultaneously turning on transistors  114  and  115  placing resistors  104  and  105  in parallel. 
   Thus, in the operation of system  80 , the incremental control of color light output from color LED  90  enjoys a single increment while the colored light output of color LED  91  enjoys three illumination increments while color LED  92  enjoys a total of six possible increments of colored light output. As a result, it will be apparent that the output of LED  90  is very coarsely controlled having a single output increment while the output of color LED  91  is more finely controlled having three illumination increments and the output of color LED  92  is very finely controlled having six possible incremental output levels. As a result, the control available in system  80  provides for substantial flexibility in more finally controlling certain color illumination levels relative to other illumination levels. 
   It will be apparent to those skilled in the art from the foregoing descriptions that the present invention system is not limited to any particular number of incremental controls for each and every color LED in the illumination system. It will be equally apparent to those skilled in the art that the present invention incremental color-blending illumination system is not limited to the use of three color LEDs. It will be recognized that the use of three color LEDs which, may for example, be red, blue and green light producing LEDs is a convenient and flexible system. However, a smaller or greater number of LEDs may be used without departing from the spirit and scope of the present invention. 
   While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.