Refrigeration – With indicator or tester – Diverse function indicators or testers
Reexamination Certificate
2000-12-21
2004-05-25
Tanner, Harry B. (Department: 3744)
Refrigeration
With indicator or tester
Diverse function indicators or testers
C062S153000, C062S298000, C068S012020
Reexamination Certificate
active
06739145
ABSTRACT:
This invention relates to a configurable electronic control unit designed to perform control functions in a wide variety of applications. The applications range from the control of appliances to implementation of control functions in commercial, industrial and automotive environments. Some examples of applications are refrigerators and washing machines in the field of appliances, HVAC (Heating, Ventilation and Air-Conditioning) and security controls in residential and commercial environments, and passenger compartment climate control in the automotive area. The controller is configurable in a variety of ways to provide flexibility and optimisation of control in the intended application, at low cost.
BACKGROUND
Control systems are used to regulate the operation of a device or system in a desired manner. This activity, in most cases, involves the control of one or more physical parameters such as temperature, pressure, level, flow, position, speed, and the like. To perform such a function it is generally necessary for the control system to sense and measure the value of the physical parameters, compare the measured values with the requirement and then operate one or more actuation devices (e.g. motors, valves, heaters) to automatically adjust the values of these parameters to desired levels. Depending upon the physical parameters involved, various transducers/sensors are used to convert the value of the physical parameter to a signal suitable for processing by the control system. In electrical/electronic control systems the conversion is to a suitable electrical parameter e.g. voltage, current, resistance, while in electro-pneumatic or mechanical systems the conversion is generally to a suitable mechanical property e.g. presssure, displacement. The selection of a transducer/sensor for a specific application depends upon the physical parameter that is required to be measured as well as the type of signal to which the conversion is to be made.
Electronic controls provide inherent advantages over other types of controls, in the vast majority of applications. For this reason, electronic controls are replacing electromechanical and electropneumatic controls in an increasing number of applications. We shall therefore limit our analysis to electronic controllers and all subsequent references to controllers and control systems shall pertain to electronic controllers and control systems.
The various types of transducers/sensors have different interface requirements and produces output signals with different characteristics. The control system has to provide the necessary interface conditions required by each transducer and possess the ability to process the signals received from it. This makes it necessary for the control system to provide different interface signals for each type of transducer/sensor.
In like manner, the various output devices that are required to be actuated by the control system inorder to bring about the correction or “control” of the sensed physical parameter, differ in their requirements for actuation DC motors and AC motors for example, have different drive requirements. In some applications using AC loads simple ON-OFF control of the load is required, while in other applications phase-angle control or integral-cycle control or integral half-cycle control may be necessary. Similarly, in controlling DC loads a simple ON-OFF control may be adequate while in other applications pulse-width-modulation output is necessary. Likewise, different types of power switching have differing requirements for operation. Triac-firing requirements are very different from the requirements for switching relays or contactors. For each case the electronic circuitry in the controller has to change inorder to provide compatibility.
User interfaces also exist in a wide variety of forms, each requiring differing interfaces to the electronic control system. Analog devices such as potentiometers, for example, interface differently from digital devices such as keyboards. Similarly, remote control devices require a special interface which varies depending on the type of remote control used-viz. radio-frequency, infrared, ultrasonic. Also display devices come in many varieties—e.g. LED, LCD, vacuum-fluorescent—each type requiring different interface signals.
Several electronic control systems in use today are based on microprocessors/microcontrollers that use software/firmware for defining the operation of the system. However, the various options described in the preceeding paragraphs, are not implementable through changes in software. Therefore in present designs the desired options are achieved by modifying the design and providing circuitry for each case. This implies that a control system designed and made for one type of sensor/transducer will not work with another transducer/sensor without making significant changes to the hardware. The electronic circuitry requirements are different for each of the interfaces. What is therefore required is that the circuitry is tailored for each interface. This requirement is achieved in one of 2 forms in existing designs. The less expensive designs are “hardwired” for a particular set of interfaces. A different “hardwired” version is used for each combination of interfaces. This results in a number of “models” or variants that differ only in the interface specifications. More expensive controllers, on the other hand, are designed in a modular fashion, with the input and output interfaces designed as separate modules. There are a number of different types of modules available, one for each of the various interface options. The controller can be configured for various interface options by installing interface modules as required. This configuration may also be changed as required. However, the modular construction still requires physical change of modules for converting from one interface option to another. This implementation generally comes at a significant cost, and is hence applied only to relatively expensive products.
An additional constraint of existing electronic controls which are typically designed around microprocessors/microcontrollers which are programmed to perform the desired control actions is that the microprocessors/microcontrollers are very limited in terms of interfaces. This limitation stems from the fact the architecture of these devices is compute-oriented rather than control-oriented. The actual environment of a control application typically involves the processing of a significant number of signals and devices (e.g. sensors, switches, motors, etc.) some of which are analog in nature. Consequently, a significant amount of circuitry is required in addition to the microcontroller—such as latches, decoders, drivers, multiplexers, analog-to-digital converters, digital-to-analog converters, signal-conditioning circuitry, etc. Some more expensive microcontrollers are available today that incorporate some additional circuitry such as analog-to-digital converters. PWM circuits, etc. However, these devices also require substantial additional circuitry in the majority of applications as the internal circuitry is still quite limited and involves compromises with the implementation of other functions. As a result, the application does not realise the full benefits of an electronic solution. U.S. Pat. Nos. 4,158,759, 4,367,387, 4,399,352, 4,406,945, 4,431,893, 4,481,393, 4,504,716, 4,533,810, 4,367,387, and 4,504,716 are examples of such electronic controls for applications in various appliances.
Some reconfigurable electronic controllers are also known. U.S. Pat. Nos. 5,306,995, 5,412,291, 5,619,614, and 5,647,231 describe some reconfigurable electronic controllers. However, the inventions covered by these patents are limited to only washing machines and dryers, and are at the same time relatively expensive to implement as they make use of fairly computation-intensive algorithms utilising fuzzy-logic implementations on microprocessor-based hardware. The limitations cited above in the case of microprocessor-based implementations are also applic
Needle & Rosenberg P.C.
Tanner Harry B.
Vasu Tech Limited
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