Abstract:
A digital electronic control unit that provides an efficient, miniature, reliable and cost-effective control mechanism for use in household and commercial appliances. It further is capable of real-time-based control, remote control and networking.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of international patent application PCT/IN99/00029, filed Jul. 5, 1999 and designating the United States of America, and of international patent application PCT/IN99/00031, filed Jul. 16, 1999 and designating the United States of America, and their specifications are incorporated herein in their entireties by this reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a digital electronic control unit that may include real-time clock-based control, remote control and networking capabilities for controlling the functions of domestic and commercial appliances such as washing machines, refrigerators, dishwashers, electric ovens, and the like. 
     BACKGROUND 
     Many modern appliances incorporate control elements that are common in the nature of their control action as well as the parameters that are controlled. For example, temperature control is a common requirement in several different appliances such as refrigerators, washing machines, dish-washers and electric ovens. Similarly, on-off control of fractional horsepower AC motors is also common to all the appliances mentioned above, besides many others. Timer based control is yet another of the common requirements in many appliances. These requirements extend to several different commercial appliances also. 
     The control mechanisms currently employed in each of these appliances are often widely different from each other. In addition, there are generally several different control mechanisms employed in each appliances, often as many as one separate control device for each controlled parameter, with each of the control devices being control device for each controlled parameter, with each of the control devices being wired together in a final circuit to perform the desired overall control function in a coordinated manner. This manner of implementation is inefficient and expensive when compared with the capabilities that emerge with the use of an integrated system of control in which the advantages offered by modem electronics technology are utilized to the fullest to provide an integrated, miniaturized implementation that is both cost-effective and efficient in terms of operation, implementation and energy consumption. 
     Some of the common parameters for control in appliances are: 
     1) Temperature 
     2) Liquid Level 
     3) On-Off control of fractional horse-power ac or dc motors. 
     4) Time sequences 
     5) Events—such as switch closures/openings. 
     In addition, some common requirements are: 
     1) Audio output (e.g. to alert users when attention is required). 
     2) Push-button/rotary adjustments of control parameters by the user. 
     3) Display of user-selections/events/parameter values by visual means—indicators or displays. 
     An implementation of the various control functions in single-chip form results in a flexible “electronic control element” that provides the maximum advantages of low-cost, small size, ease of implementation and high reliability. There are no known equivalent implementations available today. 
     Microcontroller-based implementations for some control parameters, such as temperature, are known. U.S. Pat. Nos. 4,158,759, 4,367,387, 4,399,352, 4,066,945, 4,431,893, 4,481,393, 4,504,716, 4,533,810, 4,367,387 and 4,504,716 disclose examples of such electronic controls for various appliances. These come close to realising some of the advantages but fall short in respect of optimal implementation of some of the common requirements, such as triac-firing control, a.c motor protection controls and interfaces to sensors. These requirements generally entail the incorporation of additional external circuitry and interfaces that dilute the effectiveness of the implementation. 
     Many modem control systems that are used for industrial or commercial applications incorporate the following features: 
     1) Real-time-clock (Time-of-day) based control actions. 
     2) Networking of various devices inorder to share resources or data, as well as to provide remote access to a device over the network. 
     3) Remote control using a hand-held remote control device. 
     The use of computers in control systems has further increased the need for such intercommunications. Finally, the rapid growth of the Internet and its fast expanding reach into offices and homes in the movement towards the “networked society” of the near future is expected to generate the demand for internetworking the various systems. These developments have led to the need for communication abilities even in the average devices of the home. It is therefore expected that domestic appliances would also require such capabilities. 
     Most designs of devices with such capabilities utilise microcomputers or microcontrollers as the key component for control. While this approach works very well, it is not the most cost-effective or efficient for many applications. In particular, the cost-sensitive, mass-volume application area of domestic appliances require special interface circuits, such as AC power switching devices, for which additional hardware is needed when using microcontrollers. This additional hardware can easily increase the cost and size of the control for the appliance very significantly. The use of special custom hardware provides a better solution, but existing designs of such custom hardware are very specialised to a particular application or appliance. Each appliance product therefore needs its own dedicated design of custom hardware. 
     The most desirable solution is one in which a specially-designed hardware suitable for the entire range of appliances, is configured for use in each specific product. Such a design would provide the flexibility of microprocessor-based designs at significantly lower cost and size. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a digital electronic control unit that provides an efficient, miniature, reliable and cost effective control mechanism for use in appliances intended for household and commercial applications, such as washing machines, refrigerators, dishwashers, ovens, and the like. It further relates to a flexible, digital electronic control unit for use in domestic and commercial appliances, that provides the capabilities of real-time clock-based control, remote control and networking. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described with reference to the accompanying drawings: 
     FIG. 1 shows an electronic control unit according to this invention, using potentiometers for providing user-variable input. 
     FIG. 2 shows a digital electronic control unit including real-time clock, remote control interface, and network interface, according to this invention, using potentiometers for providing user-variable input. 
     FIG. 3 shows an alternate embodiment of the unit, using switches for providing user-variable input. 
     FIG. 4 shows an embodiment in which the entire electronic control circuit excepting the power supply, external sensing elements, user variable means and external switching devices, is implemented as an Application Specific Integrated Circuit (ASIC). 
     FIG. 5 shows an embodiment in which the entire digital electronic control circuit including the real-time clock, remote control interface unit and netwok interface unit except the power supply, external sensing elements, user variable means and external switching devices, is implemented as an Application Specific Integrated Circuit (ASIC). 
     FIG. 6 shows an alternative embodiment in the form of a ASIC in which the non-volatile memory is also external to the ASIC. This facilitates the use of larger capacities of non-volatile memory. 
     FIG. 7 shows the internal structure of the output drive and protection circuit. 
     FIG. 8 shows the transformerless power-supply used to provide power to the electronic control unit. 
     FIG. 9 shows an application of the electronic control unit in a washing machine. 
     FIG. 10 shows an application of the electronic control unit in a refrigerator. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Referring to FIG. 1 of the drawings, items  1   a - 1   d  show the external sensing elements. Sensor drive circuits  2   a - 2   d  provide the bias signals for the sensors. Analog multiplexer  3  selects the signal from one of the sensing elements based on the selection data from the Central Control Unit  6  which is then converted to digital form by analog-to-digital converter  4 . This digital output is adjusted for sensor linearity, offset and sensitivity by linearity, sensitivity and offset correction circuit  5  that receives the correction factor data in digital form from non-volatile memory  17 . This corrected digital output is supplied to central control unit  6  which stores the data. User input is received by means of external potentiometers  12   a - 12   c  and is used by the central control unit  6  along with the stored digital data received from the linearity, sensitivity and offset correction circuit  5  to generate the control signal for correcting the sensed parameter. This control signal is passed through digital filter  7  to remove noise and then applied to the input of digital demultiplexer  8  which routes it to one of the control latches  9   a - 9   f  under the control of the central control unit  6 . The output of each control latch is connected to an output drive and protection circuit  10   a - 10   f . Each output drive and protection circuit drives an external switching device  11   a - 11   f  to actuate the relevant part of the appliance to correct the sensed parameter. Said central control unit  6  includes circuitry for defrost operation (not shown) and for start relay operation (not shown), if required for the appliance. The central control unit  6  drives a display drive unit  13  for displaying user input or sensed parameter value on an external display unit  14 , and also an audio drive unit  15  for providing audio output through an external audio transducer  16 . A Clock Circuit  18  and non-volatile-memory  17  are connected to various points in the circuit as indicated. 
     In FIG. 2, the central control unit  6  receives time-of-day data from real-time clock unit (C) which enables it to perform control actions based on time-of-day requirements. A remote-control interface unit (R) connected to said central control unit  6  provides the ability to receive user input data remotely form a hand-held remote control unit. A network interface unit (N) connects said central control unit  6  to external devices, which may be other similar digital control units or other devices such as computers, and enables the exchange of data between the various devices in the network. A Clock Circuit  18  and non-volatile-memory  17  are connected to various points in the circuit as indicated. 
     In FIG. 3, the user variable inputs originate from external switches  20   a - 20   c , instead of potentiometers. 
     FIG. 4 shows an implementation of the electronic control unit excluding the external blocks  1   a - 1   d ,  11   a - 11   f ,  12   a - 12   c  ,  14 ,  16 ,  19 , and  20   a - 20   c  in the form of an Application Specific Integrated Circuit (ASIC)  21  to provide a solution that is both very miniature and cost-effective. 
     FIG. 5 shows an implementation of the electronic control unit including the real-time clock, remote control interface unit and network interface unit except the power supply, external sensing elements, user variable means and excluding the external blocks  1   a - 1   d ,  11   a - 11   f ,  12   a - 12   c  ,  14 ,  16 ,  19 , and  20   a - 20   c  in the form of an Application Specific Integrated Circuit (ASIC)  22  to provide a solution that is both very miniature and cost-effective. 
     FIG. 6 shows another embodiment using an ASIC  23  in which the non-volatile memory is external to the ASIC inorder to provide for larger storage capacity. A non-volatile memory interface block MI is provided in the ASIC for connecting to the external non-volatile memory EM. 
     FIG. 7 shows the internal structure of each output drive and protection circuit. Overcurrent protection  25 , over-heat protection  26  and over-voltage protection  27  circuits inside each output drive and protection circuit monitor the electrical conditions at the output of each external switching device  11   a - 11   f  and limit or cut-off the drive to it in case of overload conditions. Additionally, a soft-start drive circuit  28  provides a gradual start-up drive signal inorder to minimise stress on the external switching device  11   a - 11   f  as well as the load (appliance). 
     FIG. 8 shows the transformerless power-supply  29  of 2 to 8 volts used to provide power to the digital electronic control unit. A capacitive voltage dropping network  30 , with a voltage clamping zener diode  31  reduces the input high-voltage AC voltage to a low value. This low value AC voltage is then rectified and filtered by a diode  32  and then filtered by a capacitor  33  to produce a low voltage d.c. supply that feeds power to the circuit. 
     FIG. 9 shows an application of the electronic contol unit in a washing machine  34 . A water level sensing element  35  placed inside the wash tank senses the water level in the tank, a temeperature sensing element  36  inside the wash tank senses the temperature of the water while a detergent level sensing element  37  placed inside the detergent supply tank senses the detergent level. The water-fill valve  38 , heating coil  39 , detergent-fill valve  40 , agitator motor  41 , motor-reversing switch  42  and water-drain valve  43  are controlled by the electronic control unit  45  based on the signals received from the various sensing elements and from the user setting switches  44 . The status and user settings are displayed on the machines user-interface panel  46  and when required, alarms are annunciated on the audio unit  47 . 
     If required, a handheld remote-control unit (RC) is also used to control the user settings and receive status information remotely. A real-time-clock (CL) on the front panel of the washing-machine displays time-of-day information and can be used to set control actions, e.g. turning-on or turning-off the washing-machine at programmed times during the day. A network (NW) connects the washing machine to other appliances in the home and to home computer (not shown), to provide computer controlled operation from within the home. 
     FIG. 10 shows an application of the electronic contol unit in a refrigerator  48 . A temperature sensing element  49  placed inside the freezer compartment senses the temperature near the cooling coils  50 , another temperature sensing element  51  placed inside the main compartment senses the temperature inside that compartment while a third temperature sensing element  52  senses the temperature of the compressor housing. A door switch  53  located on the door frame senses the open-close condition of the refrigerator&#39;s door. The digital electronic control unit  54  receives the signals from each of these sensing elements and operates the compressor unit  55 , circulating fan  56 , refrigerator light  57  and door-open alarm  58  based on the signals received from each of the sensing elements and switches. 
     If required, the refrigerator has a real-time-clock (RCL) display on the front-panel (FP) that is used to display the time-of-day as well as to define control actions at programmed times of day. The network interface inside the digital electronic control unit is also used to connect the refrigerator to a network (NET) in the home that connects the various appliances to a central home computer (not shown) for monitoring and control. 
     Sensing elements  1   a - 1   d  (which may be linear or non-linear transducers) are driven by sensor drive circuits  2   a - 2   d  and produce analog voltage signals in response to sensed parameters. These analog voltage signals are applied to the inputs of analog multiplexer  3 . Analog multiplexer  3  outputs the signal from one of the sensing elements to analog-to-digital converter  4  under control of channel-select signals received from the central control unit  6 . Analog-to-digital converter  4  produces a digital output that is the equivalent of the analog voltage supplied at its input. This digital output corresponding to the signal received from the selected sensing element, is received by linearity and sensitivity and offset correction circuit  5  and modified by it, using data stored in non-volatile memory  17  at the time of manufacture of the digital electronic control unit, to correct for non-linearities, offsets and sensitivity deviations in the sensing element&#39;s output. This produces a corrected, digital sensed parameter value. The central control unit and the linearity and sensitivity and offset correction circuit are digital logic circuits. 
     The corrected sensed parameter value is stored by the central control unit  6  which receives these values for each of the sensing elements. In addition, the central control unit  6  also receives user-supplied inputs from potentiometers  12   a - 12   c  or switches  20   a - 20   c  . The values of these inputs and the stored parameter values are evaluated by the central control unit  6  in accordance with control data that is supplied by the non-volatile memory  17 . The result of the evaluation is in the form of a digital value that is output from the central control unit  6  to the input of the demultiplexer  7  alongwith selection signals that determine the output to which the result is routed. The sequence of evaluation is repeated for each output of the demultiplexer in a repetitive manner. 
     The central control unit  6  also includes circuitry for defrost operation and start relay operation, if required for the appliance. 
     In addition, the central control unit  6  also outputs digital signals for driving the display drive unit  13  and audio drive unit  15  in accordance with control data supplied by non-volatile memory  17 . 
     The output from the demultiplexer is stored in one of the control latches  9   a - 9   f  based on the selection control signals generated by the central control unit  6 , and is used to enable/disable the corresponding output drive and protection circuit  10   a - 10   f . Each output drive and protection circuit  10   a - 10   f  when enabled by its corresponding control latch  9   a - 9   f  generates the signals necessary to drive the external switching device  11   a - 11   f  inorder to actuate the relevant part of the appliance to correct the sensed parameter. The output drive and protection circuit  10   a - 10   f  also monitors the load conditions continuously and deactivates the drive to the external switching device  11   a - 11   f  if overload conditions are encountered. 
     A Clock Circuit  16  based on a quartz crystal oscillator in the 32 KHz-25 MHz frequency range generates all the timing signals necessary to operate each circuit block while a Power Supply  18  supplies the necessary voltage and current to each circuit block of the electronic control unit. 
     A real time clock unit (C) provides time-of-day input to the central control unit  6  for enabling control actions based on time-of-day values. A remote control interface unit R connected to said central contrl unit  6  makes it possible for the user to input data remotely, instead of from the front panel of the digital control unit, with the help of a hand-held remote control device, which may be an infrared, ultrasonic or radio-frequency remote control transceiver. A network interface unit (N) connected to said central control unit  6  provides the facility to connect the digital control unit to other devices, such as other similar digital control units or computers, inorder to exchange information. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.