Apparatus for detecting presence of person inside room having do

Details Apparatus for detecting presence of person inside room having do Apparatus for detecting presence of person inside room having do

1991-08-29

1992-10-06

Ng, Jin F.

Communications: electrical

Condition responsive indicating system

With particular system function

340521, 340523, 340541, 340565, G08B 1900

Patent

active

051535602

ABSTRACT:
An apparatus for detecting the presence of a person or persons inside a room having a door. The apparatus comprises a pyroelectric infrared sensor and a piezoelectric air pressure sensor. The infrared sensor detects movement of a person and produces a signal indicating the movement. The air pressure sensor detects opening and closing of the door and produces a signal indicating the opening and closing. A logic device including monostable multivibrators, AND gates, and an OR gate is connected between the outputs of the two sensors. When the signal indicating the movement is applied to the logic device later than the signal indicating the opening and closing, the logic device produces a signal indicating the entry of a person. When the signal indicating the opening and closing is applied to the logic device later than the signal indicating the movement, the logic device produces a signal indicating the exit of a person. These signals are processed by the logic device to know the presence or absence of a person.

REFERENCES:
patent: 3990063 (1976-11-01), Schuman
patent: 4195286 (1980-03-01), Galvin
patent: 4590460 (1986-05-01), Abbott et al.
patent: 4882567 (1989-11-01), Johnson

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