| 摘要 |
PURPOSE:To increase noise resistance when rain fall is detected, by integrating values corresponding to an extended pulse width. CONSTITUTION:A rain drop detection circuit 81 outputs a rain drop detection pulse with a level corresponding to the size of rain drops passing through a detection area while a pulse extension circuit 1 outputs a pulse signal obtained by extending the pulse width of the rain drop detection pulse according to the level thereof. A comparator 2 compares an output from the circuit 1 with a threshold V1 and give comparison output '1' while the output of the circuit 1 is larger to be supplied to a wiper action timing circuit 3 through a line 88. The circuit 3 integrates the input signal through an LPF to form a wiper driving signal. Thus, rain fall can be detected by removing noise even when the noise overlaps the line 88.
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