Optical module reduces smoke-detector false alarms

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Built with two LEDs, two photodiodes, and an analog front end (AFE), the ADPD188BI integrated optical module from Analog Devices reduces smoke-detector false alarms. The photometric front end provides high ambient light rejection and reduces power consumption to enable longer battery life, while the LEDs minimize false alarms often caused by steam and dust.

All of the integrated components are housed in a custom 3.8×5.0×0.9-mm, 24-lead LGA package that prevents light from going directly from the LED to the photodiode without first entering the smoke detection chamber. Engineered to meet UL217 requirements, as well as EN54/14604 specifications, the ADPD188BI employs two LEDs, a blue 470 nm and an infrared 850 nm, to separate particle sizes, increasing the ability to detect and classify smoke types and reject nuisance sources. A backscattering design with closer proximity of the LED to the photodiode reduces circuit board size and allows for smaller smoke detectors.

The optical module also includes two external sensor inputs, three 370 mA LED drivers, and a burst accumulator that permits 20 bits per sample period. Data output and functional configuration of the ADPD188BI are handled over a 1.8 V I2C interface or SPI port.

Now in full production, the ADPD188BI optical module costs $4 each in lots of 1000 units. An evaluation board, the EVAL-ADPD188BIZ-SK, costs $60 and provides a simple means of evaluating the ADPD188BI for smoke and aerosol detection applications.

To learn more, visit www.analog.com

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