Carrier Corporation

United Technologies Corporation

Thomas W Essig

William O Shreeve

Laurie L Werbowsky

Rajendra K Shah

An electronic thermostat having a safety feature includes a controller which sends control signals to circuitry used for activating a system for conditioning air. The control signals are used to control the active state of the system for conditioning air. Furthermore, safety cutoff circuitry is incorporated into the thermostat whereby the safety cutoff circuitry is used to override the control signal sent from the controller when a predetermined temperature is reached in the space being heated or cooled.

Electronic thermostat having safety feature

An electronic thermostat having a short circuit protection feature has a controller which sends control signals to circuitry used for activating and deactivating a system for conditioning air. Short circuit protection circuitry monitors the circuitry within the thermostat and indicates to the controller when a short circuit has occurred. When a short circuit is detected, the controller sets its control signal to deactivate the system for conditioning air for a predetermined period of time.

Thermostat having short circuit protection

An improved duty cycle timer provides a duty cycle control signal having alternate 'on' and 'off' intervals of different logic states. The timer utilizes integrated circuitry having first and second independent clock sources respectively driving first and second multistage, binary counters. One counter measures the 'off' interval and the other counter measures the 'on' interval. Each counter provides a signal representative of the completion of the interval which it measures, and that signal is connected to a resetting input of the opposite counter for initiating the measuring interval of that opposite counter. Typically, one interval is longer than the other. The duty cycle control signal is provided by the output of one of the counters. In an illustrated embodiment, the duty cycle timer controls operation of a defrost mechanism for a refrigeration circuit and the 'off' interval is longer than the 'on' interval. Associated 'hold' circuitry is operative to suspend operation of the duty cycle timer when some particular demand is satisfied, but resumes operation of the timer from where it stopped when the particular demand returns.

Growing community of inventors

Fort Wayne, IN, United States of America

Thomas W Essig