| 摘要 |
PURPOSE:To provide effective sensing function for a smoke sensor through actual operation and improve the sensing precision by setting voltage of a constant voltage circuit a little lower than that of a battery, enhancing the decomposition ability of the smoke sensor and cutting off a misoutput of a detecting circuit that is generated when voltage is extremely reduced at the operating time of a starter or some other time. CONSTITUTION:A smoke sensing circuit 1 generates an output signal of a high level when sensing smoke. A constant voltage circuit 5 is applied for driving the smoke sensing circuit. When a voltage of an automotive battery is reduced extremely, a comparator 2 generates an output to have a transistor 4 ground the output of the detecting circuit 1, on account of which the output is therefore cut off. Apparatuses such as an air purifier and so on which are connected to an output terminal Vout will not perform any malfunction. On the other hand, when the battery has a normal rated voltage, the sensor senses smoke with high decomposition ability. The constant voltage circuit 5 is, at this time, set to a little lower voltage with respect to the battery voltage. Except where the battery voltage is set to an extremely low value at the starting time of a starter or some other time, the constant voltage circuit 5 will keep a constant voltage so that the detecting circuit may be operated correctly. |
