Sensing algorithm for standing and moving human body at room temperature is shown in Figure 7. The algorithm is consists of three steps: Starting point (normal states): detection 1 (temperature detection of moving human body), and detection 2 (temperature detection of a standing human body). During this step, hardware is initialized by MCU firmware, chopper is opened, while LED is in “off state”, and the interruption of MCU enables the “on-state”. Then, the next is detection 1: if human body was detected, LED will turn on and timer starts counting for 5 seconds, MCU will be interrupted that leads to off-state. Otherwise, it will return to the starting point. After 3 seconds, chopper will open, the timing delay will be 100msec, and the interruption of MCU will be enabled. Finally, if human body was detected at detection 2, it will return to detection 1. Otherwise, MCU will reset the timer after 2 seconds and will proceed to the initial step.
This algorithm, uses time delay of 100msec for MCU in order to reduce thermal noise between Fresnel lens and PIR sensor.