Vehicle head lamp monitoring circuit - has photocell and reference signals fed to comparator with logic control to operate warning device

摘要

The vehicle lighting circuit is fitted with a photocell to monitor the outside illumination and operate a warning if the lights are not switched on in poor visibility. The output of the photocell is compared with a reference level, by a comparator circuit. A logic control circuit operates in two modes, to operate the alarm if the switch is off in poor visibility as well as operate the alarm if the switch is closed in good visibility. The same alarm circuit is used for both modes so that the driver has adequate warning if he leaves his lights on in good visibility ie in instances when sunlight obscures the dashboard indicators, and there is a danger of the lights being left on when he leaves the vehicle.