Circuit arrangement for continuously controlling the brightness of signalling lamps

摘要

These signalling lamps are used in traffic light systems. The aim of the invention is a circuit arrangement which automatically adapts the brightness of the signalling lamps to the ambient brightness. On the one hand, distinct recognisability of the signalling lamps is to be achieved without there being a blinding effect and, on the other hand, the life of the incandescent lamps is to be increased and electrical energy saved. The essence of the invention consists in that the incandescent lamps are driven with a lower power system voltage. To generate this low power system voltage, the values of the ambient brightness and the magnitude of the power system voltage are processed in a microcomputer. The microcomputer uses these values to program a programmable timing element which is started at the zero crossing of the power system phase and outputs a signal for driving the signalling lamps in the rising phase. Depending on the time programmed, the current flow angle in the signalling lamp changes and with it the brightness. The field of application is traffic light systems for controlling road traffic at junctions.