Abstract:
A multiple state opto-electronic switch, having at least three states, includes a moveable member operable to move over a plurality of discrete positions. The moveable member has a plurality of radiation modulating segments from which a plurality of groups are defined. An emitting source is operable to emit radiation. A plurality of detectors, sensitive to the radiation, are each mounted proximate and in fixed position relative to motion of the movable member. Each of the plurality of discrete positions corresponds to a respective mapping between the plurality of detectors and a selected group of the radiation modulating segments. Each group of radiation modulating segments controls the radiation passing from the emitting source to each of the detectors. The plurality of detectors thereby generates a set of output signals responsive to a position of the moveable member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims priority to U.S. provisional application No. 60/241,283 filed Oct. 17, 2000 entitled “Multi-State Optoelectronic Switch.” 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention generally relates to electrical or electronic switches. This invention more particularly relates to a multiple state opto-electronic switch.  
         BACKGROUND OF THE INVENTION  
         [0003]    A number of schemes have been previously developed for user controls on devices such as appliances—e.g., washing machines, dryers, ovens, etc. Perhaps the most common in use have been mechanical switches having electrical contacts. Many of these switches include critical electromechanical contacts, which may be unreliable in service and prone to wear. Such switches can also be expensive, especially if quality of materials and workmanship is increased in the pursuit of reliability and extended useful life.  
           [0004]    Absolute position encoders using opto-electronics may be used as multi-state switches. Such devices have constraints not applicable to control switches, however, and accommodating those constraints adds to cost and otherwise limits design in ways not relevant for control switches. For example, a common type of rotational absolute position encoder, such as a typical industrial single-track Gray code shaft encoder, may be used. Such an encoder will typically be constructed to permit operation through an entire 360 degrees of rotation (or even include multi-turn counting capability) and is designed, at some cost, to eliminate or mitigate problems arising from metastability in intermediate or transitional switch positions. In contrast, a switch operating, for example, as a control knob typically needs to sweep through only a limited arc, can permit arbitrary angles between setting positions and may have an old mechanical detent or similar mechanism to prevent or inhibit persistence in intermediate positions.  
           [0005]    Thus a need exists for switches having lower cost, higher reliability, durability and/or imposing fewer mechanical design constraints than do previously-developed implementations.  
         SUMMARY OF THE INVENTION  
         [0006]    The opto-electronic switches disclosed herein are more reliable than mechanical switches because they eliminate critical mechanical contacts. In addition, such switches can be smaller and cost less than previously developed switches, including other embodiments of opto-electronic switches.  
           [0007]    According to an embodiment of the present invention, a switch is provided having a positional input and a set of binary (two-state) electrical or electronic outputs responsive to the positional input. In one embodiment, the positional input is rotational in accordance with the “control knob” paradigm for everyday appliances.  
           [0008]    In an application addressed by the switches according to embodiments of the invention, binary outputs representing a number of states are desired. For an eight-state switch, three binary outputs are required, a 16-state switch requires four binary outputs and a 32-state switch requires five binary outputs. In some situations, the number of required output states is not a power of two, in which case the number of binary outputs may be determined by rounding up to the next integer power of two and then taking the logarithm base two. Thus, for example, if nine states are desired, then four outputs (capable of supporting 16 states) are required. The binary outputs of the switch may be converted to electrical forms (e.g., voltages and currents) to operate the appliance that the switch controls.  
           [0009]    Embodiments typically use mechanical position settings to selectively modulate paths between radiation sources (emitters) and detectors. For economy and reliability, preferred embodiments use a single radiation emitter to excite multiple detectors. A single emitter may also be more fail-safe than a multiple emitter arrangement since the switch is less likely to be partly functional in the event of emitter component degradation.  
           [0010]    In this disclosure, an exemplary 16-state switch is discussed, although the concepts are applicable to switches with more states or fewer states. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Preferred embodiments of the invention are described in detail hereinafter with reference to the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 a  illustrates a frontal view of a multiple state opto-electronic switch, according to an embodiment of the present invention.  
         [0013]    [0013]FIG. 1 b  illustrates a side view of the opto-electronic switch of FIG. 1 a.    
         [0014]    [0014]FIGS. 2 a  and  2   b  illustrate frontal and side views, respectively, detailing the radiation modulating structures of the switch of FIGS. 1 a  and  1   b , according to an embodiment of the present invention.  
         [0015]    [0015]FIGS. 3 a  and  3   b  illustrate frontal and side views, respectively, detailing the radiation modulating structures of the switch, according to another embodiment of the present invention.  
         [0016]    [0016]FIGS. 4 a  and  4   b  illustrate frontal and side views, respectively, detailing the radiation modulating structures of the switch, according to still another embodiment of the present invention.  
         [0017]    [0017]FIG. 5 illustrates a frontal view of the switch of FIG. 1 a  and indicates alphabetic designators of the modulating segments and numeric designators of the detectors. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]    A multiple state opto-electronic switch  2  according to an embodiment of the present invention is shown in FIGS. 1 a  and  1   b . As depicted, switch  2  includes a wheel  10  and a base  13 . The wheel  10  features a circular rim  11  shaped as an offset flange, and which has been subdivided into segments  101   a ,  101   b , etc. through  101   p . In this embodiment the segments  101   a  through  101   p , collectively, are distributed over the entire circular rim  11  (i.e., 360 degrees). This is not an essential feature, however, and the segments could also, with advantage in some applications, be distributed in an arc of less than 360 degrees. In the present embodiment, each of segments  101   a  through  101   p  is either opaque (thereby preventing the passage of light), or transparent or comprise a hole/window (thereby allowing the passage of light). Wheel  10  is rotatably mounted on a support shaft  15  (FIG. 1 b ). The angular position of the wheel  10  is a physical variable that determines outputs signals generated by switch  2 .  
         [0019]    Base  13  is provided in fixed relationship relative to the rotatable motion of wheel  10 . In one embodiment, base  13  can be a printed circuit board (PCB) which can be connected to appropriate power supply voltage input and ground. PCBs provide stable and low cost platforms for both mounting and for interconnecting electronic, mechanical and electrical components. A number (e.g., four) of sensors (detectors)  4   a ,  4   b ,  4   c  and  4   d  are mounted on base  13  outside the rim  11  of wheel  10 . In one embodiment, the sensors  4   a  through  4   d  are placed adjacent at angular intervals equal to the mutual angular offsets of the segments  101   a  through  101   p . In this embodiment, the sensors  4   a  through  4   d  are mounted at offsets of 22.5 degrees (i.e., 360/16 degrees). This arrangement allows the sensors  4   a  through  4   d  to be mounted in relatively close proximity to one another. As described herein, it is the particular encoding of the segments  101   a  through  101   p  (as opaque or transparent/holes) on the rim  11  that make it possible for the sensors  4   a  through  4   d  to be mounted in these potentially advantageous adjacent positions. In one embodiment, each sensor  4   a  through  4   d  may be “turned on” if it detects light; otherwise, the sensor  4   a  through  4   d  may be “turned off.” The sensors in the switches disclosed herein may be optically sensitive transistors but this is not a critical feature. Other sensor technologies, such as Darlington transistors, enhanced contrast transistor sensors and/or binary sensors (e.g., diodes coupled to Schmitt trigger circuits) could be used within the general scope of the invention. And many other sensor technologies known in the arts may be used within the general scope of the invention.  
         [0020]    In the present embodiment, a light emitting source  12  provides a source of radiant emission and can be mounted on base  13  at a position proximate the axis of the wheel  10 . In one embodiment, light emitting source  12  can be an infrared light emitting diode (LED). Emitters of radiation other than infrared may also be used in cooperation with corresponding sensors. A light emitting source  12  illuminates the sensors  4   a  through  4   d  subject to modulation by the segments  101   a  through  101   p  on the rim  11 . In another embodiment, light emitting source  12  can be mounted on a wheel  10 , and many other arrangements are feasible.  
         [0021]    Segments ( 101   a  through  101   p ) that are opaque block radiation, whereas segments that are transparent/holes allow radiation to pass from source  12  to one or more of sensors  4   a ,  4   b ,  4   c  and  4   d . Thus, in one embodiment, the wheel  10 , may be placed in any one of sixteen positions so that a selected group of four segments (any adjacent four of segments  101   a  through  101   p ) block or permit radiation to reach sensors  4   a ,  4   b ,  4   c  or  4   d . The opaque or translucent property of each segment  101   a  through  101   p  determines a binary characteristic or state for that segment. Table 1 illustrates one embodiment for the binary states for segments A through P, generally corresponding to sixteen segments.  
         [0022]    [0022]FIG. 5 provides a frontal view of switch  2  with segments  101   a  through  101   p  generally labeled by letters A through P, and sensors  4   a  through  4   d  generally labeled by numbers  1  through  4 . Table 2 provides a mapping between segments A through P and sensors  1  through  4  for various positions of wheel  10 . Still referring to FIG. 5, in a first position, segment A is aligned with sensor  1 , segment B is aligned with sensor  2 , segment C is aligned with sensor  3  and segment D is aligned with sensor  4 . This is also shown as wheel position  1  in Table 2 herein, i.e., the first entry in Table 2. In wheel position  1 , segment A is aligned with sensor  1  and so the binary encoding as determined by the opaque or translucent property of segment A determines the radiation reaching sensor  1 , and thus determines the output of sensor  1 .  
         [0023]    Provided that a consistent convention is applied, any segment may be encoded opaque or transparent and binary zero may be represented by either polarity of any of a variety of signal types as is well known in the art. In wheel position  1 , segments A, B, C and D are aligned with sensors  1 ,  2 ,  3  and  4 , respectively; in wheel position  2 , segments B, C, D, and E are aligned with sensors  1 ,  2 ,  3 , and  4 , respectively; and so on.  
         [0024]    Table 3 shows the hexadecimal words produced by sensors  1  through  4  at the 16 positions of the wheel  10  for the binary states assigned to segments A through P in Table 1. Binary values represented by groups of four bits are commonly termed “hexadecimal words” in the art and herein. For example in wheel position  1 , Table 2 shows that segments A, B, C and D are aligned with sensors  1 ,  2 ,  3 ,  4 , respectively. Table 1 shows that segments A and C are encoded binary 0, whereas segments B and D are encoded binary 1; thus the output of sensors  1 ,  2 ,  3 ,  4  (for wheel position  1 ) are determined by the encoding of segments A, B, C, and D, respectively. Thus, for wheel position  1 , those outputs will be binary 0, 1, 0, 1 respectively equivalent to a hexadecimal word of “0101” or a decimal value of ten. This decimal value is formed by interpreting the four bits of the hexadecimal word as having weights of successive powers of two—i.e., 1, 2, 4, 8. Thus, in the example, ten is calculated as zero times one, plus one times two, plus zero times four, plus one times eight. This set of outputs corresponds to the first entry (row) of Table 3 and the shown successive wheel positions correspond to successive entries of Table 3.  
         [0025]    As shown in Table 3, the encoding of segments A through P is arranged so that in each of the sixteen positions of the wheel  10 , a unique hexadecimal output word is defined and is represented by each of the four sensors  1  through  4  being turned off or on. Typically a mechanical arrangement will be deployed to ensure that the wheel  10  is held aligned to one of the desired sixteen positions, rather than to any intermediate position or state. Many suitable mechanisms are well known in the mechanical arts.  
         [0026]    One aspect of an embodiment of the present invention is the particular placement of the opaque segments on the rim  11  of wheel  10 . Referring to FIG. 5, with four sensors, labeled as  1 ,  2 ,  3  and  4 , and with the wheel having sixteen segments, labeled A through P, the segments will be aligned with the sensors in the sequence shown in Table 2. In one embodiment, a sensor which is conducting current—i.e., one for which radiation is reaching the sensor via a translucent segment—is considered to be “on” or a binary 1; conversely, a sensor for which radiation is blocked by an opaque segment is considered to be a binary 0, With this convention for the wheel segments translucent and opaque as shown in Table 1, the specified binary states will be produced. Circuits and binary values may operate with opposite conventions without loss of utility. In the example cited above, the sensors are placed sequentially in a single quadrant and in close proximity to each other. Alternatively, the sensors can be located in other positions on the perimeter of the circle defined by wheel  10  and achieve a unique set of binary outputs (with a properly configured wheel).  
         [0027]    In general as described with reference to FIGS. 1 a ,  1   b , wheel segments can be used to block or allow radiation from reaching the sensor. Several alternative embodiments are shown in FIGS. 2 a ,  2   b ,  3   a ,  3   b ,  4   a  and  4   b . FIGS. 2 a ,  2   b  show plan and elevation views of selected portions of the switch  2  of FIGS. 1 a ,  1   b . In FIGS. 2 a ,  2   b , radiation absorbing walls  18  are provided along radii of the wheel  10 . Thus a path  21  taken by radiation emitted from source  12  to sensors  4   a ,  4   b  is a simple beam (sensors  4   c ,  4   d  are not shown in FIGS. 2 a ,  2   b ). The truncation of path  22  shows the effect of opaque segment  101   b.    
         [0028]    [0028]FIGS. 3 a ,  3   b  show (in plan and elevation) an embodiment in which a wheel  10  has reflecting and absorbing sectors  102   a ,  102   b , which determine whether more or less radiation reaches each sensor  4   a ,  4   b , etc., thus generating an “on” or “off” state in the sensors. The embodiment of FIGS. 3 a ,  3   b  can be implemented with sensor and emitter chips on a PCB base. Still referring to FIGS. 3 a ,  3   b , the radiation passing from source  12  to sensor  4   a  along a path  23  is reflected by reflecting sector  102   a  which may typically have a glossy finish. Conversely, radiation absorbing sector  102   b  may typically have a matte finish and the radiation following path  24  is significantly attenuated. Radiation is inhibited from a direct path by opaque wall  30  and walls  19  prevent or reduce stray radiation.  
         [0029]    [0029]FIGS. 4 a ,  4   b  show (in plan and elevation) an embodiment of the switch  2  in which the radiation from source  12  is reflected down the channel, rather than shining directly from the source  12  emitter to the sensors. Possible paths for reflected radiation is shown as beams  25 ,  26 ; however, the radiation may typically be scattered and travel along many paths. The embodiment shown in FIGS. 4 a ,  4   b  can also be implemented with a chip-on-the-board construction.  
         [0030]    Base  13  provides a mounting for amplifiers, decoders, etc., to process and condition the sensor outputs which represent the hexadecimal words reflecting of the contemporary switch position setting. However the inclusion of additional circuitry on the PCB is an economy and a convenient, rather than an essential, feature.  
         [0031]    Within the general scope of the invention, other embodiments will be apparent to a person of ordinary skill in the relevant arts. For example modulating segments, can be mounted on a movable member that slides, rather than rotates, in relative motion to the sensors. This would provide mechanical elegance in that the sensors could be arranged linearly. Users may prefer a sliding arrangement to a rotatable control knob in some applications. Another example within the general scope of the invention might involve the use sensors (detectors) that are not radiation based, for example the segments could be implements as magnetic cores and the sensors as inductors. Or Hall effect sensors or many others types may have advantages in particular applications. The invention should be regarded not as limited by the embodiments disclosed but only by the claims herein.  
                             TABLE 1                           Binary state for each       segment                Segment   State                       A   0           B   1           C   0           D   1           E   1           F   1           G   1           H   0           I   1           J   0           K   0           L   1           M   1           N   0           O   0           P   0                      
 
         [0032]    [0032]                                                                         TABLE 2                           Segment facing sensor for each       position of the wheel            Wheel   Sensor                Position   1   2   3   4                    1   A   B   C   D       2   B   C   D   E       3   C   D   E   F       4   D   E   F   G       5   E   F   G   H       6   F   G   H   I       7   G   H   I   J       8   H   I   J   K       9   I   J   K   L       10   J   K   L   M       11   K   L   M   N       12   L   M   N   O       13   M   N   0   p       14   N   O   P   A       15   O   P   A   B       16   P   A   B   C                    
         [0033]    [0033]                                           TABLE 3                           Binary word state generated at each       position of the wheel.            Wheel   Binary   Decimal       Position   State   State                    1   0101   10       2   1011   13       3   0111   14       4   1111   15       5   1110   7       6   1101   11       7   1010   5       8   0100   2       9   1001   9       10   0011   12       11   0110   6       12   1100   3       13   1000   1       14   0000   0       15   0001   8       16   0010   4