Control of stepper motor operated gas valve

摘要

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.

主权项

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; and a 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.