The road traffic light signals have designed to be powered from traffic controllers of road intersections, which have “Zero Crossing” function, so there is smoothing in alternation of electric power, to protect the light sources of the traffic lights, from phenomenon of “Arc -Flashing “.
The “Zero Crossing” function applied to traffic controllers for decades, but now the need for this is incumbent upon more, because of big difference of cost between the incandescent or halogen lamps and the LED signal modules, as and the sensitivity of LED signal modules due of electronic circuits which containing.
The use of electromagnetic relays, regarded as improper quality power supply for powering of traffic lights, because due to mechanical contacts which feature, create the phenomenon of “Arc-Flashing”, causing damage on circuits of LED signal modules.
So in case that a traffic light, should be installed in application, in which there is no traffic controller of road intersections or other device that has a “Zero Crossing” function, an intermediate solution is the use of electronic relay (Solid State Relay), where in Open state exhibit a small leakage voltage of the order of 30 to 50 V, but which prevents the phenomenon of “Arc-Flashing”.
For these reasons and in order to prevent extensive damage to traffic lights installations that do not have “Zero Crossing” function, we recommend as an intermediate solution to the use of electronic relay (Solid State Relay).