Headlamp monitoring circuit - with photosensitive part to indicate if lights not on if illumination too low

摘要

An impulse generator is formed by two complementary transistors coupled into a photo-sensing circuit to monitor the outside illumination of the vehicle. The system is connected to the live terminal of the ignition switch to ensure that the circuit only operates if the ignition is switched on. The system is further coupled to the live terminals of the headlamps, so that if these are switched on the warning system operates if any headlamp fails. The warning system operates a flashing lamp and/or buzzer with the flashing/buzzing rate determined by the RC circuit in the system.