... after connecting the electricity, that is because all PIR sensor and IC should have starting time.. After 1-2mins, ... left to right or from right to left, the sensor will be sensitive. But when people walk from the ... to down or even from bottom to top, the sensor will be insensitive or does not work. Tomeet the ... lens, so that all the four sides of the probe will be sensitive, but the up-down direction is ...