At its core, the PCB electromagnetic relay operates on the principle of electromagnetism. The relay consists of several key components： a coil, an armature, contacts, and a spring. When an electrical current passes through the coil, it generates a magnetic field that attracts the armature, which is mechanically linked to the contacts. This movement can either close or open a circuit, depending on the design of the relay.

    In its idle state, the armature is held in place by the spring. When the coil is energized, the magnetic field overcomes the spring's tension, causing the armature to move. In a normally open (NO) relay, this movement will close the circuit, allowing current to flow. Conversely, in a normally closed (NC) relay, the armature's movement will open the circuit, interrupting the current flow. Once the current to the coil stops, the magnetic field dissipates, and the armature returns to its original position due to the spring, thereby resetting the relay.