ZHCSH75A September 2017 – December 2017 ADS7142
PRODUCTION DATA.
A passive infrared (PIR) sensor is a commonly used sensor to detect motion by measuring infrared light emitted from any object that generates heat. PIR sensors are small, inexpensive, low-power, rugged, have a wide lens range, and are easy to use. PIR sensors are commonly used in security lighting and alarm systems used in indoor environments. When there is no motion or heat-emitting object in the vicinity of the sensor, the PIR sensor output is a DC voltage which is typically specified in the PIR datasheet. When a source of heat, such as a person or animal, comes into the sensor field of view, then the PIR sensor output changes. The amplitude of this signal is proportional to the speed and distance of the object relative to the sensor and is in the range of millivolts peak-to-peak. PIR sensors are often followed by a signal conditioning stage which amplifies the IR sensor output. A PIR sensor can be interfaced with the ADS7142 to make an ultra-low-power, autonomous PIR motion detector. The Autonomous Modes of the ADS7142 with threshold monitoring enables the system to put the host MCU into a low-power sleep mode and wake up the MCU only when motion is detected by the PIR sensor. Figure 119 shows a typical block diagram for an autonomous PIR motion detector using the ADS7142.