Patent Publication Number: US-6661354-B2

Title: Potentiometer with embedded signal circuitry

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation-in-part of U.S. application Ser. No. 09/567,847, filed May 9, 2000, the disclosure of which is incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to electrical potentiometers that convert angular or linear mechanical movement or position to an electrical output. 
     Various schemes exist to convert angular or linear mechanical position to an electrical output. An example of such a converter is a potentiometer, which convert position to an output voltage by acting as a resistive divider. The analog output from a potentiometer can then be converted to a digital format, if required. 
     Potentiometers are well know in the art. An example of a potentiometer is disclosed, for example, in U.S. Pat. No. 4,081,782, the disclosure of which is incorporated by reference. Such devices typically include a housing that encloses a resistive element. A rotor, rotated by a shaft, carries a rotating element that electrically interconnects with the resistive element, such as a film resistor, as the rotor is rotated to generate an electrical signal having a voltage characteristics defined by a point of contact with the resistive element. For example, the rotor may carry a rotating contact element that mechanically contacts the resistive element as the rotor is rotated, to generate the electrical signal. 
     Some potentiometers convert linear movement into the voltage signal using a slider rather than a rotor, as also understood by those skilled in the art. 
     SUMMARY OF THE INVENTION 
     The present invention converts mechanical movement of a device input into a signal that can be applied to particular purposes. In accordance with the present invention, a potentiometer and associated signal conditioning and processing circuitry are embedded together as a single unit for simplicity of assembly into particular applications, and for reliability. 
     One aspect of the invention provides an electronic device comprising a substrate having opposed first and second major surfaces; a potentiometer coupled to the first major surface of the substrate, the potentiometer having an output terminal on which an electrical signal is produced; and a programmable electronic device coupled to the second major surface of the substrate, the programmable electronic device having an input receiving an indication of the electrical signal. 
     One aspect of the invention provides an integrated potentiometer comprising a substrate having first and second substantially opposed major surfaces; a potentiometer formed on the first major surface of the substrate, the potentiometer comprising an actuation shaft, the potentiometer varying at least one electrical signal based on movement of the actuation shaft; and programmable electronic circuitry attached to the second major surface of the substrate, the programmable electronic circuitry electrically coupled to the first major surface. 
     One aspect of the invention provides an integrated potentiometer comprising a substrate having first and second opposed major surfaces; a potentiometer formed on the first major surface of the substrate, wherein the potentiometer is configured to generate an electrical signal in response to movement of an input device; and electronic circuitry attached to the substrate, wherein the electronic circuitry comprises supervisory power processing circuitry, and a logic device for processing the electrical signals generated by the potentiometer, and wherein at least some of the electronic circuitry is attached to the second surface of the substrate. 
     One aspect of the invention provides an electronic device comprising: a printed circuit board having first and second substantially opposed major surfaces; a potentiometer formed on the first major surface of the substrate, the digital potentiometer comprising: an actuation shaft having rotational and axial movement; at least one resistive element formed on the first major surface of the printed circuit board for converting rotational and axial movement of the actuation shaft into electrical signals; a programmable logic device surface mounted on the second major surface of the printed circuit board, wherein: the programmable logic device is connected through the printed circuit board to the potentiometer to receive the electrical signal generated by the potentiometer; the programmable logic device is programmed to process the electrical signal generated by the digital potentiometer; and supervisory power processing circuitry attached to the second major surface of the printed circuit board for conditioning power applied to the programmable logic device; and a communication interface circuit attached to the second major surface of the printed circuit board for receiving from the programmable logic device processed signals. 
     These and other aspects of the invention may be more fully comprehended upon review of the following in conjunction with the referenced figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a potentiometer with embedded circuitry constructed in accordance with the present invention. 
     FIG. 2 is a perspective view of the lower side of a potentiometer with embedded circuitry constructed in accordance with the present invention. 
     FIG. 3 is a top view of the potentiometer shown in FIG.  2 . 
     FIG. 4 is a side view of the potentiometer shown in FIG.  2 . 
     FIG. 5 is a front view of the potentiometer shown in FIG.  2 . 
     FIG. 6 is a schematic diagram of an electronic device embodying an integrated potentiometer in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring first to FIG. 1, a particular embodiment of the integrated potentiometer device constructed in accordance with the present invention is shown in functional block diagram form. The integrated potentiometer device receives input power through a power input  21  to a supervisory power supply protection component  23 . The supervisory power supply protection component  23  may comprise several discrete elements that regulate the power to provide a stable, clean power source; filter the power to remove high frequency noise and protect other elements of the electronic circuitry from voltage spikes; and provide a reset function to ensure proper start-up of the other elements of the circuitry. 
     An input device  25  provides functional input for the integrated device constructed in accordance with the present invention. In one embodiment the input device is a potentiometer. The potentiometer provides a variable resistence. Accordingly, the potentiometer provides a varying electrical signal, generally a voltage. 
     Programmable logic  27  receives power from the supervisory power supply protection component  23 , and potentiometer signals from the potentiometer input device  25 . The programmable logic  27  performs signal conditioning and signal processing functions on the potentiometer signals. The programmable logic is preferably programmable either by the device manufacturer, or by the manufacturer of equipment using the device, to perform functions that are appropriate for the application. The programmable logic may be one-time programmable, or may be repeatedly programmable. The logic may be a programmable microcontroller, such as a RISC-type controller. The programmable logic produces conditioned and processed signals appropriate for use by other, external devices. 
     An output function converter  29  provides an output interface for making the conditioned and processed signals generated by the programmable logic available for application to other devices. 
     In accordance with the present invention, a potentiometer that converts linear or rotational mechanical movement into digital electronic signals is formed as an integral unit with circuitry such as programmable logic that performs signal processing and other functions related to the operation of the potentiometer. In one embodiment, the programmable logic  27  is secured to the same electronic board or substrate as the potentiometer  25  itself. 
     A particular embodiment of an integrated potentiometer device  30  constructed in accordance with the present invention is shown in FIGS. 2 through 5. Referring first to FIG. 2 the integrated potentiometer device  30  is seen in a perspective view from its underside. The integrated potentiometer device  30  includes a potentiometer portion  25  mounted on a substrate  31  that comprises a circuit board having upper and lower major surfaces. 
     The circuit board substrate  31  is formed of conventional circuit board material, such as PCB FR-4, with multiple layers. The circuit board substrate  31  includes circuitry (not shown) on both major surfaces thereof, with the intermediate layer(s) (not shown) containing circuitry interconnecting the surface circuitry as appropriate for particular applications, in a manner known to those skilled in the art. 
     The upper major surface of the circuit board substrate  31  includes the potentiometer  25 , while the lower major surface of the substrate  31  includes circuitry for converting the position and movement of the potentiometer  25  into predetermined electrical signals, generating potentiometer output signals. The circuitry for generating potentiometer output signals may be of substantially conventional design for a potentiometer, which will be familiar to those skilled in the art, and is not here shown in detail. For example, the encoder may be of the type described in the aforementioned U.S. Pat. No. 4,081,782 previously mentioned or other conventional types. In accordance with aspects of some of these conventional designs, a potentiometer includes a rotor with an electrical contact attached to a surface of the rotor. The contact makes electrical contact with a resistive element or elements formed so as to provide a resistance of the device bearing on the position of the rotor. In some embodiments, an actuation shaft is attached to, and extends axially from, the rotor. The actuation shaft permits user input (rotational and axial) to the potentiometer. 
     Still referring to FIGS. 2-5, a housing  35  encloses the upper potentiometer portion  25  of the integrated potentiometer device  30 . The housing  35  includes an upwardly extending hollow cylindrical fitting  37 . The actuation shaft  33  of the potentiometer  25  extends through the hollow cylindrical fitting  37 . The hollow cylindrical fitting  37  may be externally threaded so that the cylindrical fitting may be attached to a counsel or similar device mounting structure (not shown) that is formed with mating threads. The upper surface of the housing may also include an externally threaded portion  41  to provide an additional option for attaching the integrated potentiometer to a counsel or similar mounting structure. 
     Referring now to FIGS. 2,  4 , and  5 , the lower portion of the housing  35  includes downwardly extending mounting feet  43  that may be used in mounting the integrated potentiometer device  30  in particular applications. For example, the feet  43  may abut a mounting surface (not shown) to position the integrated potentiometer device  30  in its operating environment. In certain embodiments or implementations, openings (not shown) may be provided through the feet  43  to permit mounting screws or other attachment devices (not shown) to be inserted through the housing to secure the integrated potentiometer device  30  to a mounting structure. 
     Referring again to FIG. 2, one or more circuit elements  45  are mounted on the lower major surface of the substrate  31  (opposite the potentiometer mounting). The circuit elements  45  include the supervisory power supply protection  23 , the programmable logic  27 , and the output converter  29 . Some elements may be mounted on the upper major surface of the substrate, alongside the potentiometer  25 . However, in the embodiment illustrated, the upper surface of the substrate encompasses only the potentiometer  25 . 
     The programmable logic  27  may be any of a number of devices of types that are known to those skilled in the art. For example, the programmable logic may include an application specific integrated circuit (ASIC) containing circuitry for processing the signals generated by the encoder. Such circuitry may include circuitry for modifying or conditioning the potentiometer signal, such as signal filters. Such signal filters may include de-bounce circuitry familiar to those skilled in the art. The circuitry of the logic may also include signal modifiers to identify angle of rotation and direction of rotation of the shaft, or to detect the speed with which the potentiometer shaft is manipulated. The circuitry may also provide access to multiple functions in response to particular rotational or axial movement of the shaft. Additional functions may be provided to permit hardware or software keying of functions, to enable or disable embedded features and options. Furthermore, the programmable logic preferably includes memory for programming to accomplish specific tasks desired of the circuitry. The memory may be included on an integrated logic device, or may be a separate device. The memory may be one time programmable, or may be repeatedly programmable. Thus, the memory may include EPROM or EEPROM devices. In a particular preferred embodiment, the logic is provided in a programmable microprocessor, such as a Reduced Instruction Set Controller (RISC-type) microprocessor with embedded memory. Alternatively, programmable logic arrays, and other programmable devices may be included. 
     Integrated into the programmable logic or microprocessor may be debounce circuitry analogous to the circuitry contained in a conventional MC 14490 device, application-specific decode logic, and other functions that previously performed in discrete separate devices. 
     The programmable logic  27  may be programmed in such a manner that how the programmable logic interprets signals from the potentiometer  25  can be modified to provide a different output at the output converter  29  (FIG. 1) for a given input supplied by the potentiometer  25 . An advantage of the integrated device  30  illustrated and described herein is that the programmable logic can be programmed so that it can be reprogrammed by manipulation of the actuation shaft  33  of the potentiometer  25  itself. For example, the programmable logic can be programmed so that, in certain modes of operation, the signals produced by the potentiometer  25  in response to particular manipulations of the actuation shaft  33  alter features of the programmable logic, such as selecting modes of operation, or adjusting particular performance characteristics of the signal processing functions. 
     The programmable logic or microprocessor  27  is preferably mounted on the lower major surface of the substrate  31  using surface mount technology. Surface mounting eliminates the protrusion of electrical pins through the substrate. Multilayer substrates with multiple layers of embedded electrical circuitry can be used in combination with such surface mount technology to permit the installation of electric devices on both sides of the substrate board. The circuitry on the lower major surface of the circuit board substrate therefore includes surface mount pads (not shown). Thus, the potentiometer  25  and the programmable logic  27  may be mounted on the opposed major surfaces of a single circuit board substrate  31 . 
     Additional electronic devices  45  may be attached to the lower major surface of the circuit board substrate  31 . For example, if the supervisory power supply protection function and the output converter function are not integrated into the programmable logic  27 , devices for performing those functions may be separately attached to the lower surface of the circuit board substrate. 
     The integrated potentiometer device  30  includes a plurality of input and output pins  47 . The input and output pins  47  extend vertically from a horizontal extension  49  of one edge of the circuit board substrate  31 . In the illustrated embodiment shown in FIGS. 2 through 5, the input and output pins  47  are elongate vertical metal cylinders that provide electrical connections to which a variety of external devices may be attached. Circuitry for conducting power and/or signals between and among the input and output pins  47 , the programmable logic  27 , the potentiometer  25 , and other circuit elements  45  mounted on the circuit board substrate  31  may be applied to either surface major surface of the circuit board substrate, or may be embedded in an intermediate layer of the circuit board substrate. The information of such circuitry on the circuit board substrate will be apparent to those skilled in the art. Those skilled in the art will also recognize that other forms of input and output contact points may be provided on the circuit board substrate. 
     Potentiometers are used in a variety of applications. One common application is the volume control for an audio device, such as a radio, in which the rotational position of the shaft  33  is converted into a particular volume level. In such an application, an absolute potentiometer may be most appropriate, wherein a particular rotational position of the shaft  33  is always associated with a particular signal, such as to designate a particular volume level. In many such applications, the shaft  33  may also function as the on/off switch for the audio device. For example, briefly depressing the shaft  33  axially turns the audio device on or off. In alternative applications, depressing the shaft  33  of the potentiometer  25  may produce different results in different circumstances. For example, depressing and shortly thereafter releasing the shaft  33  may function as an on/off switch or switch the device between different modes of operation, while holding the shaft in a depressed position for a longer period of time may access a menu of options that may be selected by the user. A single rotary control could therefore provide menu access to multiple functions, eliminating the need for multiple separate controls. For example, a single rotary control on an audio device can be programmed using the present invention to provide controls for treble and bass control, and for balance and fade, as well as power on/off and volume. The functions provided in response to the manipulation of the encoder shaft  33  are determined by the programmable logic included in the integrated potentiometer device  30 . 
     In certain other applications, a relative potentiometer is appropriate. A relative potentiometer generates a signal indicating relative movement of the rotor shaft. Again, the functions provided are determined by the logic included in the integrated potentiometer device  30 . 
     An exemplary detailed specific implementation of the integrated potentiometer device  30  of the present invention is illustrated in the circuit diagrams of FIG. 6 for a particular application. In the diagram of FIG. 6, a potentiometer  101  is provided on one surface of a printed circuit board (PCB)  103 . The potentiometer is, in some embodiments as previously discussed, and in some embodiments is a surface print potentiometer. The potentiometer receives a high voltage signal and a low voltage signal. In the case of the device of FIG. 6 the high voltage signal is a V CC  voltage signal  105  and the low voltage signal is a ground signal  107 . The potentiometer provides a common mode signal COM  109 . The COM signal indicates a position of, for example, a rotor controlling the variable resistance of the potentiometer. 
     The V CC  and ground signals are provided by a voltage regulator  111 . The voltage regulator is mounted to an opposing side of the PCB. The voltage regulator in some embodiments includes a surge protector and other similar power supply related circuitry. 
     The COM signal of the potentiometer is provided to a processor  123 . The processor is also mounted on the opposing side of the PCB. The processor receives power signals from the voltage regulator, and a clock signal  125  provided by an oscillating circuit  127 . The processor performs signal processing functions in accordance with the configuration of the processor. In some embodiments the processor is a programmable logic device, an ASIC, a digital signal processor (DSP), a RISC processor, or various other types of processors. 
     The processor also receives a feedback signal FB  131 . The feedback signal is provided to the processor. In various embodiments the processor provides output signals based on the values of the COM and FB signals. 
     In the embodiment of FIG. 6, the application is a motor controller. Accordingly, the processor also receives a motor indicator signal as the feedback signal. In one embodiment the motor signal indicator is a signal indicating an angular position of a shaft of a motor. Accordingly, operation of the motor results in movement of the shaft coupled to the motor, with the shaft controlling position of a potentiometer. The motor potentiometer provides the feedback signal to the processor. 
     The processor, in one embodiment, includes analog to digital converter capability and internally generates signals indicative of the voltage, and thus the position, of the potentiometer and the motor potentiometer. In one embodiment, the processor performs a comparison of the two signals, and commands the motor to rotate the shaft. Thus, for example, a processor provides a first output signal  131  and a second output signal  133 . The output signals form a differential signal. 
     The differential signals are provided to a signal driver  135 . The signal driver increases the signal strength and otherwise amplifies the signal provided by the microprocessor as necessary to provide drive signals to a motor. In one example, the signal driver is a differential buffer. In one embodiment the signal driver includes a pair of op-amps  137 ,  139 , each op-amp receiving one of the differential signals and a reference signal, with the op-amps providing an open loop gain to drive motor signals  141 ,  143 . 
     The motor signals are provided to the motor, with the differences in the voltages of the motor signal driving the motor one direction or another. In some embodiments the processor also includes a dead band, in which no motor actuation is provided. 
     Although the present invention has been described above in particular embodiments, it will be clear from the foregoing discussion that numerous variations and modifications will suggest themselves to those skilled in the pertinent arts. Such variations and modifications should be considered within the spirit and scope of the present invention, defined as the claims and their equivalents supported by this disclosure.