Light obstruction type smoke sensor

Details Light obstruction type smoke sensor Light obstruction type smoke sensor

1999-01-14

2000-07-25

Wu, Daniel J.

Communications: electrical

Condition responsive indicating system

Specific condition

340578, 340584, 340630, 250574, 356438, G08B 1700

Patent

active

06094143&

ABSTRACT:
A driving unit generates a driving current corresponding to a light generation control signal CTL supplied from a light generation controlling unit. The driving current is supplied to an LED. Light emitted from the LED impinges on a light receiving circuit through a space of a monitoring area. The received light level of the light receiving circuit is converted into a received light level signal RLV in an A/D. The received light level signal RLV is supplied to a smoke detecting unit and the light generation controlling unit. The received light level signal RLV is monitored in a short period by the smoke detecting unit. When the received light level signal RLV is equal to or lower than an alarm level, an alarm signal ALM is output. The light generation controlling unit compares the received light level signal RLV with a reference level in a long period. The light generation control signal CTL is increased or decreased so that the level difference between the received light level signal RLV and the reference level is eliminated.

REFERENCES:
patent: 4695734 (1987-09-01), Honma et al.
patent: 4930095 (1990-05-01), Yuchi et al.
patent: 5574435 (1996-11-01), Mochizuki
patent: 5705988 (1998-01-01), McMaster
patent: 5708414 (1998-01-01), Peltier et al.
patent: 5831537 (1998-11-01), Marman
patent: 5864293 (1999-01-01), Lewiner et al.

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