1. Field of the Invention
This invention relates generally to smoke detectors and more particularly is directed towards a new and improved, temperature-compensated, reflected light optical smoke characterized by a minimum number of components.
2. Description of the Prior Art
Conventional optical smoke detectors typically comprise one or more light sources operating in conjunction with one or more photocells with one light source often serving as a reference for comparison with the light output of the other sources. In an obscuration type detector smoke passing between one light source and a photocell visible to the source will reduce the output of the photocell and alarm circuitry, set to a predetermined voltage level output of the photocell, will be actuated. In a reflected light type of detector, the light source is directed at a zone that is visible to the cell. If smoke is present in the zone, light reflected from the smoke will fall on the cell, increasing its output. Alarm circuitry will again be actuated in the event of such an increase.
Insofar as many of the components in a smoke detector circuit are temperature sensitive, many detectors are provided with rather complex means to compensate for changes in ambient temperature. In general any increase in the complexity of the circuit adds to the cost of the circuit because of additional components and assembly requirements.
Accordingly, it is an object of the present invention to provide a simple, low cost, reflected light optical smoke detector characterized by a minimum number of components.
Another object of this invention is to provide a temperature-compensated, reflected light optical smoke detector having selected components with complementary temperature coefficients that automatically correct for changes in ambient temperatures.
A further object of this invention is to improve the reliability of smoke detectors by reducing the number of parts thereof.