A single-chip CMOS smoke and temperature sensor for use as an intelligent
fire detector is proposed. The proposed smoke sensor measures smoke
density based on the light-scattering method.
The temperature sensor is integrated with the smoke sensor not only to sense
heat from a fire but also to compensate for the temperature dependency of the
smoke sensor.
The prototype chip includes an on-chip photodiode (PD), pixel circuit,
correlated double sampling (CDS) circuit, and analog-to-digital converter
(ADC). The prototype chip was fabricated using a 0.35-mu m CMOS process
and was placed inside the smoke detection chamber, while the thermistor for
the temperature sensor is placed outside the chamber.
The measurement results show plusmn 1% smoke detection accuracy over the
range 4% ~ 25% and plusmn1degC temperature-sensing accuracy over the
range 25degC ~ 95degC. The power consumption of the prototype chip is 220
nW, excluding the infrared light-emitting diode (IR LED).
