When the relay module is working, the electromagnetic iron is energized, which pulls down the armature to make contact between D and E, and the working circuit is closed. When the electromagnet loses its magnetism, the spring pulls up the armature and cuts off the working circuit. Therefore, a relay is a switch that uses an electromagnet to control the on/off of a working circuit.

The benefits of using relays to control circuits: using low voltage to control high voltage; Remote control; Auto-Control. A relay is an automated electrical switch that operates through electromagnetic induction.

The working principle and characteristics of relays.

A relay is an electronic control device that has a control system (also known as an input circuit) and a controlled system (also known as an output circuit). It is commonly used in automatic control circuits and is actually an "automatic switch" that uses a smaller current to control a larger current. Therefore, it plays a role in automatic regulation, safety protection, and circuit conversion in the circuit.

Electromagnetic relays are generally composed of iron core, coil, armature, contact spring, etc. As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil, thereby generating an electromagnetic effect. The armature will overcome the pulling force of the return spring and be attracted to the iron core by the electromagnetic force, thereby driving the moving contact of the armature to engage with the stationary contact (normally open contact). When the coil is powered off, the electromagnetic attraction also disappears, and the armature will return to its original position under the reaction force of the spring, causing the moving contact to be attracted to the original static contact (normally closed contact). This suction and release achieves the purpose of conduction and disconnection in the circuit. For the "normally open" and "normally closed" contacts of a relay, they can be distinguished as follows: the static contact that is in a disconnected state when the relay coil is not energized is called a "normally open contact"; The static contact in the connected state is called a "normally closed contact".