Across the most of the world’s regulations now require smoke detectors to be installed in homes, schools, public and commercial buildings. In addition to sounding an audible alarm when a fire breaks out, smoke detectors must also communicate an alarm notification to a remote control location, such as the local fire station. To detect smoke an LED inside the smoke sensor illuminates and measures the current corresponding to the amount of light output by a light receiving sensor. The current is converted to a voltage by an op-amp, and the voltage is read using an A/D converter. The LED inside the sensor illuminates at regular intervals controlled by a timer in order to reduce the power consumption by sampling the smoke volume intermittently.
Renesas’ RL78/G1x integrate on-chip the peripheral functions necessary for use in smoke detector design, making it possible to reduce the overall product size. Low-voltage operation contributes to extended battery life, which is essential for detectors that must operate over extended periods of time.
System Block Diagram
|Block||Semiconductor device||Recommended products||Features, etc.|
|Main controller||MCU||78K0/Kx2-L||20-pin, low power consumption|
|H8/38602R Group||32-pin, low power consumption|
|RL78/G1x||32 MHz, 16-bit general purpose, True low power|
|EEPROM||R1EX24xxx Series||I2C bus interface *1|
|R1EX25xxx Series||SPI bus interface *2|
|Op-amp.||HA1630xxx Series||CMOS low power consumption, small package, low voltage operation|
|μPC358GR||Bi-polar single power, low power consumption, small pakage|
|MCU peripheral||Reset IC||RNA519xx Series||Variable detection voltage|
*1 I2C: Inter-Integrated Circuit
*2 SPI: Serial Peripheral Interface
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