Vehicle windshield and wiper with rain sensor

A motor vehicle windshield and wiper system comprising:

• a windshield having at least one glass layer;
• a wiper system having a blade on the outside of the windshield and drive means activatable to drive the blade in a predetermined pattern across a designated area of the windshield;
• first and second outer conducting members on the outside of the windshield within the designated area, said first and second outer conducting members being made of semi-transparent tin oxide and being slightly separated along a long common border to define a border resistance in parallel with a first capacitance therebetween, the border resistance being essentially infinite when dry but decreasing with water bridging the border;
• first and second inner conducting members adjacent the first and second outer conducting members, respectively, made of the same material and separated therefrom by at least the glass layer of the windshield, the first inner and outer conducting members being effective to define a second capacitance therebetween and the second inner and outer conducting members being effective to define a third capacitance therebetween in electrical series with the first and second capacitances;
• electrical oscillator circuit means comprising a comparator having a fixed reference connected to one input, a timing circuit connected to the other input, the timing circuit comprising the second, first and third capacitances in series, with the infinite resistance across the first capacitance, to form an equivalent capacitance, as de by charging and discharging current therethrough, the electrical oscillator circuit means further comprising comparator switched current means effective to charge and discharge the equivalent capacitance at a frequency determined thereby and thus varying with change in the border resistance;
• and
• additional circuit means responsive to the frequency of the electrical oscillator circuit means to produce a first mode of wiper operation when the common border is dry and a second mode of wiper operation when the common border is bridged by water.