Device for automatically adjusting the frequency of activation of a motor vehicle windscreen wiper

Claim 1

An electronic circuit for automatic adjustment of the frequency of activation of an intermittent motor vehicle windscreen wiper based upon the quantity of moisture on the windscreen, comprising: a wiper motor; means for detecting the variance in current passing through said motor wherein said means generates a proportional voltage signal (V i ); means for filtering and amplifying said voltage signal (V i ) generated by said detecting means wherein said filtering and amplifying means generates a filtered voltage signal (V 2 ); means for generating a threshold voltage signal (V s ); means for comparing said voltage signal (V 2 ) derived from said detecting means with said threshold signal (V s ) wherein said comparing means generates a control signal (V 3 ); means for controlling the power supplied to said motor responsive to said control signal wherein said controlling means simultaneously controls a first direct supply circuit for said motor and a second circuit forming a short circuit connection to said motor; means for overriding the intermittent activation of the wiper wherein said overriding means provides continuous operation for at least two wiping cycles upon initial activation of the circuit whereby said means generates a voltage signal which is added to said signal derived from said detecting means; and switch means for controlling the activation of the circuit.