Abstract: A burner control system conditions opening of the fuel control valve on proper operation of a hot surface igniter for igniting the fuel. Current flow through and voltage across the hot surface igniter is constantly monitored, and if either is not proper, the valve closes. A pair of diodes provides half wave DC current of different polarity respectively for the hot surface igniter and the valve actuator.

Abstract: A heating system controller is suitable for controlling a heating system based on a plurality of sensed control signals representing control parameters. The heating system controller has a first input suitable for being coupled to provide a control signal. The heating system controller also includes a sensor, coupled to the first input, for sensing control signals at the first input, the control signals having a first pattern, a second pattern, or a third pattern detected over at least two successive time periods. The heating system controller includes a control mechanism, coupled to the sensor for controlling the heating system based on the first, second and third patterns. The control mechanism causes the controller to change modes when the third pattern is sensed.

Abstract: A temperature control system has a thermostat which provides an on/off signal. The on/off signal has an on period and an off period and is indicative of a temperature error. The temperature control system is suitable for controlling temperature control equipment. The on/off signal is sensed and the temperature error is determined based on the on/off signal. The temperature control system is controlled based on the temperature error determined.

Abstract: The moving coil actuator of a pressure regulator has two threaded adjustment screws each mounted parallel to the actuator's path and which project through a limit surface of a carrier for the moving oil actuator. Both adjusting screws can be rotated by means of a tool, but their mounting prevents them from being moved longitudinally. Each of the adjustment screws carries a limit element, one on each side of the carrier's limit surface. The position of each of the limit elements on its adjustment screw is adjustable by means of an internal thread. In the preferred embodiment, each adjustment screw is partly enveloped by a projection on the limit element carried by the other adjustment screw, by which each limit element is secured against rotation during adjustment. The limit elements independently limit the stroke of the moving coil at each end by blocking movement of the limit surface when the actuator reaches its desired limit.

Abstract: A leak detector for a valve controlling flow of fuel to a combustion chamber employs a fuel concentration sensor in a sensing chamber placed downstream from the valve seat. The valve has a downstream chamber which is in communication by diffusion through an orifice, with a source of pressurized air. By injecting air into the downstream chamber through this orifice after the valve has closed and then measuring with the sensor the fuel concentration within the sensing chamber, excessive fuel leakage by the valve can be detected.

Abstract: The tendency of a motor-driven actuator driving against a dynamic (non-frictional) load to return upon reaching the limit switch sufficiently to again close the limit switch and create a persistent oscillation at the limit position can be prevented by placing a positive temperature coefficient thermistor across the limit switch involved. Such loads typically arise in actuators having spring-driven return capability, and can also arise when positioning air dampers and other loads where the actuator force is opposed by a spring or gravity.

Abstract: A circuit for detecting presence of a flame receives a flame signal from a standard photocell positioned to receive radiation from the flame and digitally processes the amplitude variations in the photocell's output to sense for the presence of frequencies near a frequency which is characteristic of a flame. The frequencies substantially higher than the characteristic frequency are filtered from the signal, and the remaining signal is sampled at a frequency which is preferably four times the characteristic frequency. The samples are converted to digital values and processed using a discrete Fourier transform. If the value resulting from the transform operation exceeds a preselected value, presence of a flame is essentially certain. Such digital processing allows use of a dedicated microcircuit or a microprocessor for the flame sensing function and avoids the need for many large discrete components.

Abstract: A communications system has an active master node which transmits request messages in serial bit fashion on a data bus, and a plurality of responder nodes each of which receives the request messages on the data bus and may respond to a request message with a serial bit answer message. The possiblity exists that a plurality of responder nodes may provide concurrent answer messages forming a composite signal which the active master node may not be able to recognize as containing answer messages. A low pass filter is provided in the active master node which provides as its output only those pulses in the composite signal whose length is within a predetermined interval, typically from approximately a tenth to one half of the interval for each bit in the answer messages. A counter receives the low pass filter output and provides a collision signal to the associated master node if more than a preselected number of pulses within the predetermined interval are present.

Abstract: A conventional thermostat has separate high and low temperature switches for controlling a reversible motor driving a modulating damper or valve whose position controls the temperature of an enclosure by controlling the injection and removal of heat from the enclosure. In the improvement, relay contacts control the current flow to the thermostat's heat and cool anticipator resistors, and only relay control current flows through the motor windings. This avoids degraded motor performance resulting from anticipator resistor current flow through the motor windings and makes the anticipator resistor current level independent of the motor impedance. The relay chosen is one whose activating element draws very little current to close the relay contacts. The preferred embodiment uses a solid state relay which includes a light emitting diode whose light emissions control the impedance of a semiconductor circuit forming the "contacts" of the relay.

Abstract: An electronic network of communication and processing nodes particularly suitable for control of environmental systems has pluralities of the nodes which are sources for certain types of status messages each of which comprise communication of a particular kind of information on the network. To resolve the question of which of the nodes shall furnish each type of status message, one node is designated the coordinator node, and it stores a status message source list which associates the node assigned for each type of status message with the status message type itself and transmits all or a part of the list on the network to allow each of the status message source nodes to determine therefrom their responsibility with respect to each status message type. These status message source nodes can also transmit request messages on the network by which they request responsibility for furnishing a particular type of status message.

Abstract: A fuel burner includes an electrical igniter which lights a pilot burner which then lights the main burner. Operation of each of these steps is monitored, and if any are improper, the control device reverts to lighting the pilot burner with the main burner valve shut. If the igniter is sensed as incapable of lighting the pilot burner, the pilot burner valve is shut, and an error is indicated to the operator.

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: A power control system includes a voltage follower circuit which may be interposed between a load power control circuit which adjusts the level of power applied to a load, and a variable impedance whose internal impedance prescribes the desired level of power. A feedback voltage from the output of the voltage follower circuit is compared with a corresponding voltage across the variable impedance and the difference between them is used to drive the output voltage of the voltage follower circuit toward the input voltage. The voltage follower circuit permits control by a single variable impedance of many more load power control circuits than a single variable impedance can normally handle, and without appreciably affecting the power level as a function of the impedance level. This circuit is particularly useful in a system for controlling the level of light received from fluorescent light fixtures controlled by electronic ballasts.

Abstract: A setback thermostat controlling a device which holds and changes the temperature in a space includes the capability of sensing and recording the difference between the time at which recovery to a new setpoint temperature occurs and the selected time at which this temperature is specified to be reached, and if the difference is nonzero, calculates a new time at which to begin recovery the next time a change to the new temperature is specified. The calculation of the time at which recovery begins takes account of the fact that greater time is required to achieve a one degree temperature change near the new setpoint temperature than far from it because of the additional thermal load on the space as temperature nears the new set point. A non-linear function is used to calculate the time at which recovery to the new temperature is begun. The invention is included in a method for operation of the device which changes the space's temperature.

Abstract: A burner control system for an intermittent pilot burner system uses a single pole double throw relay to control first and second electromagnetic valves respectively supplying fuel for both burners and for the main burner only. The normally open contact pair supplies the current for the first and the normally closed contact pair supplies the current for the second valve. By selecting the valve supplying fuel for both burners to be of the type which has an appreciably higher pull-in current than drop-out current, and by shunting the relay's normally open contacts with a properly selected resistor, only a single relay is necessary. This resistor is selected to supply current sufficient to hold the valve open (current greater than the drop-out value) after the valve has received pull-in current through the closing of these normally open contacts, but insufficient to open the valve. Use of a single relay reduces cost, size, and power, and increases safety of the control system.

Abstract: A method and apparatus detect a faulty air switch in a heating system which has an operation cycle comprising a plurality of operating periods. The air switch senses air flow in the heating system and causes air flow limit contacts to open when the air flow is outside a predetermined limit. The air flow is outside the predetermined limit during a first operating period of the operation cycle. A series circuit comprises the air flow limit contacts, coupled in series with other limit contacts between a limit sense terminal and an energized input terminal. The other limit contacts should be closed during the first operating period of the operation cycle. The limit sense terminal is sampled during the first operating period to determine whether the limit sense terminal is energized. Based on whether the limit sense terminal is energized, the air switch is determined to be faulty or operating properly.

Abstract: A load power control circuit which adjusts the level of power provided by a load in response to changes in the impedance across control terminals includes a control circuit which disconnects the load from the power source when the voltage across the control terminals in within a certain range. The control circuit is particularly useful in controlling fluorescent light fixtures controlled by electronic ballasts because the control circuit avoids the need for a separate on/off switch for the fixtures.

Abstract: A stop pin which has a forward end and a latching end is employed between spaced plates or walls having aligned apertures. The latching end of the stop pin has locking buttons formed on longitudinal faces of the stop pin and a shoulder spaced from the locking buttons by the thickness of the first plate. The forward end of the stop pin is inserted through the first aperture and into the second aperture. Additional axial force on the stop pin forces the lock button through the first aperture by rotating the latching end into relieved portions of the first aperture while the forward end of the stop pin opposes rotation. After the stop buttons pass through the first plate the pin straightens and is latched with the stop button and the shoulder on opposite sides of the first plates.