Two pins connect to a coil that creates a magnetic field. You can use it to control devices that need to turn on or. A 5 pin relay is a versatile electrical component used to control high-current devices with low-power signals, commonly found in automotive systems, home automation, and industrial machinery. It works in things like headlights or horns. It also works. At its core, a 5 pin relay is an electromechanical switch that is controlled by an electrical signal.