Abstract: A method and system for allowing multiple local simple communication buses to be selectively and separately connected as part of a larger, global communication bus. This interconnection is done transparently to the local buses, which may continue to operate autonomously and employ readily available and low cost devices based on time division multiplexing (TDM) protocol. A number of such TDM local buses are each provided with a switching device. A global bus and controller connects to each of the local bus switching devices. By uniquely addressing each switching device, the global controller can receive and transmit on any selected local bus, and issue commands to specific devices thereon. In a rapid fault polling mode, each local bus switching device is commanded to check its local bus devices for fault codes, and signal the presence thereof to the global controller, which can then access the local bus(es) which have the faults.

Abstract: A power controller has upstream and downstream switches in series connection to provide redundant switching for power supplied from a power source to a load. A switch operating system closes the switch closer to the load first (downstream) and then the switch closer to the source (upstream). The operating system conditions closing the downstream switch on absence of power voltage on an upstream power terminal of the downstream switch. A preferred embodiment of the operating system performs a number of real time status checks during the connection process to assure that power voltage is properly absent and present at switch terminals during the stages of the connection process. This operating system guards against supplying power to the load if either the upstream or downstream switch's pair of contacts are welded at the time the connection process starts.

Abstract: An annunciator for the conduction status of individual switches wired into a series circuit records this status as status history at regular intervals in a memory. The status history is preferably recorded as individual entries having the identification number of an open switch along with a time stamp specifying the length of time which that switch has been open. The current entry is recorded in the memory and a new entry started each time the switch for which an entry in the memory is being created closes or a switch currently receiving power opens. A controller separate from the annunciator generates a request signal and provides a request time value to the annunciator specifying the time which has elapsed since the request condition was detected. The annunciator uses the request time value to determine the probable switch conduction status at the time of the request.

Abstract: An annunciator for the status of interlock switches connected into a series circuit for supplying power from a power source to a load, includes a memory recording the status of each switch at a selectable instant. A plurality of display elements are arranged in a pattern corresponding to the pattern of the interlock switch circuit. A manually operable switch allows a user to select for graphically showing with the display either the switch status recorded by the memory or the current status of the switches. The signals controlling the display are conditioned so that the particular display element assigned to the first out switch as recorded in the memory flashes to indicate the switch closest to the power source which was not conducting at the selectable instant.

Abstract: The position of the power output member of a motor actuator which is normally controlled by a microprocessor in response to system-supplied condition signals may be set manually by providing a manually controlled selector signal to the microprocessor allowing manually controlled adjustment signals rather than the normal condition signals to form the parameters from which is derived the motor control signal. In the preferred embodiment, a first switch generates the selector signal and a second switch generates the adjustment signal. Such apparatus allows a repairer or installer to adjust a mechanical positioning system driven by the motor actuator while the positioning system is in a variety of precisely selected positions. This control system contains a feature allowing one to change position of the motor actuator's power output member either continuously or incrementally by appropriately manipulating the switch which generates the adjustment signal.

Abstract: The present invention is a method and apparatus for conditioning an AC input signal to a control system having a plurality of AC input signals. An AC system signal is substantially phase-synchronous with the AC input signal. The AC input signal is sampled a plurality of times to determine whether it is present or absent during a periodic half cycle of the AC system signal. A result value is determined which represents a state of the AC input signal determined a majority of the times that it was sampled. It is then determined whether the state of the result value has changed.

Abstract: The present invention is a method and apparatus for changing fuels used in a heating system without substantially recycling the heating system where a main flame burns fuel supplied to the heating system. A fuel changeover signal is received from a fuel selector. Flow of a first fuel to the heating system is regulated in response to the fuel changeover signal to achieve a low fire state in the heating system. A pilot flame is established in the heating system and flow of the first fuel is shut off. A fuel indicator signal is received from the fuel selector indicating a desired fuel. The main flame in the heating system which is burning the first fuel is extinguished. The pilot flame is monitored for stability and the main flame is re-established in the heating system burning the desired fuel in response to the fuel indicator signal.

Abstract: A method and apparatus determine signal quality of AC input signals to a control system where the AC input signals and an AC system signal are phase-synchronous. A read cycle, for reading the AC input signals, is scheduled to be performed during periodic cycles of the AC system signal. The presence or absence of the AC system signal is determined. A number of good read cycles are counted where the good read cycles represent the read cycles performed when the AC system signal is present. A ratio is determined between the number of good read cycles counted during a predetermined time and a total number of read cycles scheduled to be performed during the predetermined time.

Abstract: The present invention is a method and apparatus for preventing a decision made by a controller from being made based on incomplete information where the controller periodically runs a decision making routine. The controller makes decisions based on a plurality of AC input signals being present or absent. The presence or absence of the AC input signals is read by the controller during a read cycle performed during periodic half cycles of the AC system signal. The AC system signal and the AC input signals are substantially phase-synchronizes. Before the controller runs the decision making routine, the controller determines whether the presence or absence of the AC input signals has changed since the previous decision making routine. Where the presence or absence of the AC input signals has changed since the previous decision making routine, the decision making routine is delayed for a predetermined number of half cycles of the AC system signal.

Abstract: The present invention is a method and apparatus for monitoring a plurality of AC input signals to a control system. An AC interrupt signal is generated, based on an AC system signal which is substantially phase-synchronous with the AC input signals, for an interrupt time period corresponding to a time period when the AC system signal exceeds a predetermined threshold voltage. The AC interrupt signal is verified and a timer is set for a pseudo-random time value. The AC input signals are sampled when the timer has reached the pseudo-random time value to determine the presence or absence of valid AC input signals.

Abstract: A burner control system has a microprocessor for testing parameters of operation and for indicating deviations from a preset range for each. The sensors monitoring the parameters provide their outputs as analog voltages to analog to digital (A/D) converters which provide the parameters in digital form. Tests using preset voltage standards increase the likelihood of A/D converter accuracy. In addition, as operating conditions for the burner change, different preset ranges are used for each sensor output when testing them so as to provide maximum confidence of proper burner operation.

Abstract: Damper position of a damper in a heating system is monitored. The damper is movable between end positions in response to movement of a motor shaft. The motor shaft moves in response to a movement request signal. A shaft position signal is received by a position detector and has a value representative of position of the motor shaft. When the damper reaches an end position, it is determined whether the value of the shaft position signal is within a predetermined tolerance. If it is outside of the tolerance, then the system is shut down as unreliable; otherwise, the shaft position signal is recalibrated to maintain accuracy.

Abstract: An anti-bounce system for control of critical loads is provided. A control system contains two subsystems. The first subsystem functions for normal control of the critical loads, but has a relatively long information processing time. This long time might prevent the system from controlling the loads in a safe manner. The system has a second subsystem that has a very rapid processing time. Both of the subsystems are connected to the load by coupling means to monitor as a feedback signal the exact state of the loads. The second subsystem overrides the first, and disconnects power whenever there has been an interruption of power for a short period of time.

Abstract: A flame safeguard control system using a microcomputer is disclosed. The microcomputer responds to the flame signal as provided from a normal flame amplification chain and an analog-to-digital converter. A safety backup circuit in the form of a redundant flame signal detection circuit analyzes the analog signal being provided to the analog-to-digital converter. In the event that the microcomputer is unable to shut the main fuel valve off, the redundant flame detection circuit becomes operative to deenergize part of a series circuit including the relay for the main fuel valve.

Abstract: A microcomputer utilizing a crystal controlled clock and a power line responsive clock operates both the control system and into a safety timing means. The safety timing means can take the form of a pair of retriggerable monostable multivibrators that are operated to monitor the microcomputer along with a feedback circuit from a load control means. The feedback from the load control means senses the status of a safety switch means and provides the microcomputer with the ability to monitor and be monitored for safe operation.

Abstract: A flame safeguard sequencer incorporates an interlock checking means that verifies the proper status of the start or preignition interlocks in the burner system and the run interlocks of the burner system. In the event that an interlock opens during a period of time when it should not be open, the system can limit the operation of the sequence to a short time period (typically 30 seconds) to allow the interlock to reestablish a normal running state. If the correct state is reestablished, the system continues normal operation. If the correct state is not reestablished, the system is shut down on safety and a coded fault-hold indicator advises a serviceman of where to find the problem.

Abstract: A purge time hold circuit is provided in a flame safeguard sequencer to in turn provide a safe start check of a burner control system. If a flame is indicated during a prepurge period, the purge time hold means will reset to a zero status and the timer will hold until the signal clears itself. If the flame signal does not clear itself within a preset time, a safety shut down will be commanded.

Abstract: The high fire and low fire switches normally operated by a damper in a fuel burner installation are verified by a switch test function. In the event that the switches are malfunctioning, the fuel burner sequence is extended to compensate, or the sequence is terminated and annunciated. The extension of the sequence is accomplished by a time sequencer alteration means that is part of a flame safeguard sequencer.

Abstract: A safety circuit which connects a condition responsive circuit to a cyclic signal detecting circuit. In order to provide the cyclic signal detecting circuit with a continuous cyclic input, the condition responsive circuit and a cyclic redundancy checker is provided. The cyclic redundancy checker identifies a specific series of logic bits from the condition responsive circuit and responds favorably only to that series of logic bits. If any other series of logic bits occurs, the cyclic redundancy checker of the system ceases to function, thereby causing the cyclic signal detecting circuit to cease to function and it in turn opens a series contact to deenergize a critical load in a control system.