Prometeusz Jasinski, Excelitas Technologies Abstract

Title:  A lens-less SMD thermopile solution for near field people recogintion in todays thin battery operated devices

Abstract:  Up to now pyroelectric sensors in combination with a multi-focal fresnel lens were the best value solution for most applications dealing with people motion detection. But todays devices are becoming so small, compact and design oriented that the traditional approach is reaching it's limitations. Thermopiles are sensitive enough to recognize the presence of a person for distances of several meters. The solution for a realible operation however is not the high sensitivity alone but a smart algorithm to separate the signal from back ground. We have developed a sensor which consists of a single-pixel thermopile and a signal processing unit in one package, able to detect people in a range of up to 3 meters in a field of view of 120° without any optical system. In order to suppress unwanted false triggers an internal back-ground subtraction algorithm is applied. Besides motion and presence detection, also temperature measurement and monitoring features were implemented in a small SMD package. The combination of an interrupt feature and a very low power consumption of only 50µW makes this device ideal for todays thin battery operated hand-held devices.