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A controller is provided for a gas valve including a movable valve element, a main diaphragm chamber having a main diaphragm therein coupled to the valve element to displace the valve element relative to a valve opening, and a servo-regulator diaphragm for regulating flow of gas that acts against th

A controller is provided for a gas valve including a movable valve element, a main diaphragm chamber having a main diaphragm therein coupled to the valve element to displace the valve element relative to a valve opening, and a servo-regulator diaphragm for regulating flow of gas that acts against the main diaphragm, to adjust the valve element and vary the flow rate. A stepper motor is configured to move in a stepwise manner to displace the servo-regulator diaphragm to adjust the valve element and gas flow rate. The controller for the stepper motor includes a microprocessor that receives an input signal indicating an operating capacity level, and determines the steps the stepper motor must move to displace the servo-regulator diaphragm to establish a flow rate corresponding to the operating capacity level. The microprocessor generates a signal to move the stepper motor the number of steps to adjust the gas valve.

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1. A system including a controller in combination with a stepper motor operated gas valve configured to vary the gas flow rate for varying the level of heating operation of a heating apparatus, the system comprising: a valve element movable relative to a valve opening in the gas valve;a main diaphra

1. A system including a controller in combination with a stepper motor operated gas valve configured to vary the gas flow rate for varying the level of heating operation of a heating apparatus, the system comprising: a valve element movable relative to a valve opening in the gas valve;a main diaphragm chamber disposed in the gas valve;a main diaphragm disposed in the main diaphragm chamber and coupled to the valve element, the main diaphragm being configured to controllably displace the valve element relative to the valve opening in response to changes in gas pressure acting against the main diaphragm;a servo-regulator diaphragm configured to regulate flow of gas to the main diaphragm chamber that acts against the main diaphragm, to thereby adjust the valve element to vary the flow rate of gas through the valve opening;a stepper motor configured to move in a stepwise manner to displace the servo-regulator diaphragm for varying the flow of gas to the diaphragm chamber, to thereby control the rate of gas flow through the valve opening; anda stepper motor position sensor configured to detect the stepwise movements of the stepper motor;the controller having an input connector configured to receive an input signal from a furnace controller, the input signal from the furnace controller comprising a pulse-width-modulation signal having a specified duration and a duty cycle ratio indicative of a desired operating capacity level at which to operate the heating apparatus, and the controller having a microprocessor in communication with the stepper motor position sensor and the input connector of the controller to receive the input signal from the furnace controller, the microprocessor including a programmable memory encoded with one or more instructions operable to determine the number of steps the stepper motor must move to displace the servo-regulator diaphragm to establish a gas flow rate corresponding to the desired operating capacity level indicated by the PWM input signal from the furnace controller, generate a stepper motor control signal that causes the stepper motor to move the determined number of steps to displace the servo-regulator diaphragm to establish the gas flow rate corresponding to the desired operating capacity level, and compare the determined number of steps with the number of steps the stepper motor actually moves as detected by the stepper motor position sensor, to verify the position of the stepper motor;wherein the microprocessor is configured to respond to the furnace controller when the PWM input signal is received from the furnace controller by generating an output signal to the furnace controller that echoes the PWM input signal prior to generating the stepper motor control signal to move the stepper motor, thereby allowing the furnace controller to verify the correct PWM input signal was received at the microprocessor, the microprocessor is configured to respond to a PWM input signal from the furnace controller having a duty cycle below a predetermined threshold that corresponds to a reset request from the furnace controller by generating a stepper motor control signal instructing the stepper motor to displace the servo-regulator diaphragm as required to close the valve opening and shut off the gas valve, and the microprocessor is configured to generate an output signal to the furnace controller after the stepper motor has moved confirming that the stepper motor has moved the number of steps to establish the gas flow rate corresponding to the desired operating capacity level indicated in the input signal. 2. The system of claim 1, wherein the input signal is a pulse width modulated signal having a duty cycle ratio of between 4 percent and 95 percent. 3. The system of claim 1, wherein the input signal is a pulse width modulated signal, in which a duty cycle that varies between about 30 percent and about 95 percent respectively corresponds to an operating capacity level that varies between about 35 percent and about 100 percent of the full operating capacity of the heating apparatus. 4. The system of claim 1, wherein the controller is configured to generate an output signal that is a pulse width modulated signal having a duty cycle ratio less than about 30 percent, to confirm that the stepper motor has moved the number of steps to establish the gas flow rate corresponding to the desired operating capacity level. 5. The system of claim 1, wherein the predetermined threshold is a duty cycle ratio of about 30 percent. 6. The system of claim 1, wherein the controller is configured to respond to a pulse width modulated signal having a duty cycle ratio less than 30 percent that corresponds to a stepper motor position request by generating an output signal that is a pulse width modulated signal having a duty cycle ratio associated with a specific operating capacity level that corresponds to the number of steps the stepper motor has moved to reach its current position. 7. The system of claim 1, wherein the controller is configured to diagnose one or more operating problems, and to control at least one indicia device to indicate one or more diagnostic conditions. 8. A system for controlling the operating capacity level of a variable capacity heating apparatus, the system comprising: a valve element movable relative to a valve opening in the gas valve;a main diaphragm chamber disposed in the gas valve;a main diaphragm disposed in the main diaphragm chamber and coupled to the valve element, the main diaphragm being configured to displace the valve element relative to the valve opening in response to changes in pressure acting against the main diaphragm;a servo-regulator diaphragm for regulating gas flow to the main diaphragm chamber for controlling the pressure that acts against the main diaphragm and moves the valve element to vary the flow rate of gas through the valve opening;a stepper motor configured to move in a stepwise manner to displace the servo-regulator diaphragm for varying the gas flow to the main diaphragm chamber, to thereby control the rate of gas flow through the valve opening;a stepper motor position sensor configured to detect the stepwise movements of the stepper motor;a furnace controller configured to communicate an input signal comprising a pulse-width-modulation signal having a specified duration and a duty cycle ratio that is indicative of a specific level of heating operation for the variable capacity heating apparatus;a controller for controlling operation of the stepper motor, the controller having a microprocessor in communication with the stepper motor position sensor and the furnace controller, the microprocessor configured to detect the presence of an input signal from the furnace controller that is indicative of a desired operating capacity level, the microprocessor including a programmable memory encoded with one or more instructions operable to determine the number of steps the stepper motor must move to displace the servo-regulator diaphragm to establish a gas flow rate corresponding to the desired operating capacity level, generate a stepper motor control signal that causes the stepper motor to move the determined number of steps to displace the servo-regulator diaphragm to establish the gas flow rate corresponding to the desired operating capacity level, compare the determined number of steps with the number of steps the stepper motor actually moves, as detected by the stepper motor position sensor, to verify the position of the stepper motor; and generate an output signal to the furnace controller confirming that the stepper motor has moved the number of steps to establish the gas flow rate corresponding to the desired operating capacity level requested by the furnace controller;wherein the microprocessor is further configured to respond to the receipt of the input signal from the furnace controller by generating an output signal to the furnace controller that echoes the input signal, prior to generating the stepper motor control signal to move the stepper motor, to verify receipt of the input signal to the furnace controller, and to respond to an input signal from the furnace controller having a duty cycle below a predetermined threshold that corresponds to a reset request from the furnace controller, by generating a stepper motor control signal instructing the stepper motor to displace the servo-regulator diaphragm as required to close the valve opening and shut off the gas valve. 9. The system of claim 8, wherein the input signal is a pulse width modulated signal having a duty cycle ratio of between 4 percent and 95 percent. 10. The system of claim 8, wherein the input signal is a pulse width modulated signal, in which a duty cycle that varies between about 30 percent and about 95 percent respectively corresponds to an operating capacity level that varies between about 35 percent and about 100 percent of the full operating capacity of the variable capacity heating apparatus. 11. The system of claim 8, wherein the controller is configured to generate an output signal that is a pulse width modulated signal having a duty cycle ratio less than about 30 percent, to confirm that the stepper motor has moved the number of steps to establish the desired operating capacity level. 12. The system of claim 9, wherein the predetermined threshold is a duty cycle ratio of about 30 percent. 13. The system of claim 8, wherein the controller is configured to diagnose one or more operating problems, and to control at least one indicia device to indicate one or more diagnostic conditions. 14. The system of claim 13, wherein the indicia device includes one or more light emitting diodes and/or audible alarm devices. 15. The system of claim 13, wherein the one or more diagnostic conditions include at least one of whether the input signal is a valid command, whether the stepper motor has moved the required number of steps, whether the stepper motor has closed the valve opening to shut off the valve, whether there is a leak, whether there is a defective coil winding on the gas valve, and whether there is an excessive pressure within one or more valve chambers. 16. The system of claim 7, wherein: the indicia device includes one or more light emitting diodes and/or audible alarm devices; andthe one or more diagnostic conditions include at least one of whether the input signal is a valid command, whether the stepper motor has moved the required number of steps, whether the stepper motor has closed the valve opening to shut off the valve, whether there is a leak, whether there is a defective coil winding on the gas valve, and whether there is an excessive pressure within one or more valve chambers. 17. The system of claim 1, wherein the specified duration of the pulse-width-modulation signal is about 0.5 seconds. 18. The system of claim 8, wherein the specified duration of the pulse-width-modulation signal is about 0.5 seconds.