Sensor for detecting fine particles such as smoke or dust contained in the air
AssigneeNohmi Bosai Ltd.
InventorNobuyuki Ichikawa
Life of this patent
Estimating the term…
Abstract
An LD light-emitting circuit 2 comprises an analog multiplexer MP having a plurality of switches, and resistors R7, R8, R9 and R10 connected to these switches. When the temperature is not higher than a normal temperature, the resistor R7 is connected so that the amount of light emitted from the LD 1 is maintained constant. As the temperature rises, however, the resistor R8, R9 or R10 having increasing resistance is connected in response to a signal from a control circuit, in order to decrease the driving current that flows into the LD 1. This enables the LD 1 to suppress its own heating and to lengthen its life.
Claims16
A sensor for detecting fine particles such as smoke produced by a fire or dust contained in air, comprising:
- a light source;
- a light-emitting circuit electrically connected to the light source for causing light to be emitted from the light source and for keeping the amount of emitted light constant;
- light-receiving means for producing a sensor output upon detecting light scattered by the presence of fine particles in the light emitted from said light source;
- control means electrically connected to said light-emitting means for controlling a driving current of said light source;
- and
- temperature-measuring means for measuring the temperature of said light source;
- wherein said control means controls the driving current of said light source based upon the values of a temperature measured by said temperature-measuring means.
A sensor for detecting fine particles such as smoke produced by a fire or dust contained in air, comprising:
- a light source;
- light-emitting means electrically connected to the light source for causing light to be emitted therefrom;
- light-receiving means for producing a sensor output upon detecting light scattered by the presence of fine particles in the light emitted from said light source;
- control means electrically connected to said light-emitting means for controlling a non-light emitting interval of said light source;
- and
- temperature-measuring means for measuring the temperature of said light source;
- wherein said control means includes means for feeding to said light-emitting means a signal which increases said non-light emitting interval when said temperature-measuring means has detected a high temperature which is not desirable for said light source.
A sensor for detecting fine particles such as smoke produced by a fire or dust contained in air, comprising:
- a light source;
- light-emitting means electrically connected to the light source for causing light to be emitted therefrom;
- light-receiving means for producing a sensor output upon detecting light scattered by the presence of fine particles in the light emitted from said light source;
- and
- control means electrically connected to said light-emitting means for controlling a driving current of said light source;
- wherein said control means is provided with sensitivity switching means for switching the sensitivity of the sensor for detecting fine particles, and when the sensitivity of the sensor for detecting fine particles is switched by said sensitivity switching means, said control means feeds to said light-emitting means a signal for changing the amount of emitted light by changing the driving current fed to said light source so as to correspond to the sensitivity.
Dependencies are inferred from the claim text.