LED smoke detector circuit

Details LED smoke detector circuit LED smoke detector circuit

1975-10-06

1977-05-24

Caldwell, John W.

Communications: electrical

Systems

Call station

250574, 340251, G08B 1710

Patent

active

040259153

ABSTRACT:
A simplified smoke or other particle detector circuit includes a light emitting diode in series with a compensating photocell and a photocell sensing LED light scattered from particles. In parallel with the LED is a high resistance, and in parallel with the photocells is a low resistance, the resistances having a common junction coupled to a threshold circuit input as is the output of the photocells. Sensing smoke produces a photocell output which triggers the threshold device to generate an alarm signal. Failure of the LED produces a voltage at the resistance junction which similarly triggers the threshold device to alarm.

REFERENCES:
patent: 3316410 (1967-04-01), Meili et al.
patent: 3534351 (1970-10-01), Harnden, Jr. et al.
patent: 3655289 (1972-04-01), Walker
patent: 3727056 (1973-04-01), Enemark
patent: 3846773 (1974-11-01), Lintelmann et al.
patent: 3882477 (1975-05-01), Mueller
patent: 3922655 (1975-11-01), Lecuyer
patent: 3922656 (1975-11-01), Horvath et al.

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