| 摘要 |
The proposed smoke fire detector contains an electronic valve element, a power-supply unit, an alarm signal former, a current-limiting element, an integrator, a capacitor, an indicator, a binary counter, a clock pulse generator, a comparator, a current switch, a threshold element, a direct-current pulse amplifier, a reset circuit, an infrared light-emitting diode, and a photodiode. The input of the valve element is connected to the first terminalfor connecting the fire detector to the fire alarm loop, and the output is connected to the first terminal of the power-supply unit and the input of the current-limiting element. The output of the current-limiting element is connected to the input of the integrator and the first terminal of the capacitor. The second terminal of the capacitor is connected to the second terminal for connecting the fire detector to the fire alarm loop and the secondterminal of the power-supply unit. The output of the alarm signal former is connected to the input of the indicator, and the input is connected to the output of the counter, the counting input of the counter, and the input of the clock pulse generator. The first output of the clock pulse generator is connected to the timing input of the counter, the second output is connected to the first input of the comparator, and the third output is connected to the input of the switch. The power-supply terminals of the switch are connected to the corresponding terminals of the capacitor. The output of the comparator is connected to the reset input of thecounter. The second input of the comparator is connected to the output of the amplifier via the threshold element. The first power-supply terminal of the amplifier is connected to the output of the integrator, and the second power-supply terminal is connected to the second terminal of the capacitor. The third input of the comparator is connected to the output of the reset circuit. The infrared light-emitting diode is connected to the output of the switch. The photodiode is optically coupled with the infrared light-emitting diode. For the purpose to extend the operating temperature range, the fire detector contains a resistor and a low-pass filter. The output of the filter is connected to the output of the photodiode. The resistor is connected in parallel to the photodiode. |
