Honeywell G.m.b.h.

Scott M Peterson

Edward L Schwarz

John E Bohan, Jr

Vicki L Perschbacher

A self-checking temperature sensing circuit in which temperature sensitivity is provided by first and second resistive elements having positive and negative temperature coefficients respectively. The resistive elements are connected in parallel current paths, one of which includes a diode for allowing only unidirectional current flow. The resistances of the restrictive elements are determined by a circuit which periodically reverses the polarity of a voltage applied across the parallel paths.

Self checking temperature sensing circuit

A controller for a gas burner system compensates for the tendency of a flame rod sensor in the burner system to on occasion provide a spike in its signal on first lightoff of a pilot flame, by delaying the signal which causes opening of the burner system's main burner valve until the sensor signal has had a chance to reach to its normal level indicative of the presence of the pilot flame. This time varies from about 5 to 30 seconds.

Gas burner controller with main valve delay after pilot flame lightoff

A fuel valve and ignitor control system in which pull-in current for a fuel valve operating on rectified alternating current is supplied through a first normally open relay whose coil is connected in series with normally open contacts of a second relay and an intermittently operating hot surface ignitor. Normally closed contacts of the second relay are connected in series with the ignitor and the fuel valve through a holding resistor, whereby actuation of the second relay provides unrectified alternating current to the ignitor and actuates the first relay to provide pull-in current to the fuel valve, and whereby deactivation of the second relay provides holding current to the fuel valve through the ignitor.

Burner control system with continuous check of hot surface ignitor

A driver circuit for an ultraviolet detector (UV) tube discriminates between firing of the UV tube in response to ultraviolet radiation impinging on it and a high resistance short between its output terminals. A capacitor charged on half cycles of AC power applied to the circuit discharges partially when the UV tube fires. This charge is transferred to a second capacitor to create a voltage displaced from ground. Each time the UV tube fires, the steep wave front generated thereby is passed by a high pass filter to a switch which momentarily grounds the voltage on the second capacitor through a resistor. The rapid change in the switch element's voltage signifies the presence of ultraviolet radiation on the UV tube.

Circuit for detecting firing of an ultraviolet radiation detector tube

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.

Fuel burner valve operator circuit with intermittent ignition

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.

Fuel burner having an intermittent pilot with pre-ignition testing

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.

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Eden Prairie, MN, United States of America

Scott M Peterson