| 摘要 |
PURPOSE:To adjust the intermitted time of operation of a windshield wiper depending on the quantity of raindrops to enable accurate operation, by converting the output of a raindrop detecting piezoelectric element into digital signals, counting the signals and driving the wiper with the intermitted time depending on the counted value. CONSTITUTION:A piezoelectric element 1 converts raindrop vibration into an electric signal, which is applied to a shaping circuit 6 to shape the wave form of the signal to send out a pulse signal. Such pulse signals are applied to a counter circuit 7 so that the pulse signals are counted. When the counted number has reached a prescribed value, a pulse signal is sent out to a wiper drive circuit 5 to operate a windshield wiper. According to this constitution, even if the output of the piezoelectric element 1 fluctuates minutely, the output timing of the pulse signal from the counter circuit 7 is not adversely affected, so that the intermitted time of operation of the wiper is controlled to be appropriate depending on the quantity of raindrops. |
