Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1982-03-12
1984-11-06
Rowland, James L.
Communications: electrical
Condition responsive indicating system
Specific condition
250574, G08B 1710
Patent
active
044815069
ABSTRACT:
A photoelectric smoke sensor wherein a photo diode having a junction capacitance of 100 pH or less is employed and a resistor having a high resistance value of the order of mega-ohms is connected in series with the photo diode to obtain a photo output through the resistor, so that the voltage of the photo output may be sufficient to be directly subjected to comparison by the comparator without high-gain amplification even if the driving current for a light emitting diode is reduced. This enables omission of a high-gain amplifier and accordingly enables omission of a shield case for the circuits of the sensor which has been required to eliminate noises. Further this photoelectric smoke sensor is arranged so that the light emitting diode is driven intermittently, the photo output is compared with a reference voltage in synchronism with the driving of the light emitting diode, and the output from the comparator is data-read in by flip-flops at the timing of the decay of the photo pulse, to reduce the current consumption and simplify the circuit formation.
REFERENCES:
patent: 4260984 (1981-04-01), Honma
Fogiel Max
Hochiki Kabushiki Kaisha
Myer Daniel
Rowland James L.
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