Detector for protecting air dams of motor vehicles

摘要

A motor vehicle sensing and warning circuit is described that includes a series of N Schmitt triggers with MOS P-channel and N-channel enhancement devices included in a single monolithic structure to perform waveform generation, sensing, comparison and control functions. The Schmitt triggers are configured to deliver as an astable oscillator in circuit with a sensing antenna through a balance circuit as well as deliver as an audio oscillator to drive a piezo element to alert the driver of the presence of an invading object that should be avoided. Shaping and conditioning of the reference waveform are generated by the free running oscillator, as is a comparison function in association with a series of strobing diodes resulting in a strobed output summing function between a Schmitt sensing trigger and a Schmitt reference trigger associated with the free running oscillator. The resulting inverted output is then connected to a pair of signal comparators which have their non-inverting inputs connected to a set point reference source. In operation, as the object to be avoided is sensed by the antenna, the strobed output is modulated by such effects. As a result, an amplified output signal appears at the inverted inputs of the signal comparators. As the output state of the comparators goes HI, visual and audio indicators adjacent to the operator of the vehicle are driven to active states. Evasive action then can be initiated.