1. Brief introduction of relays

A relay is an electrical control device that makes a predetermined step change in the controlled quantity in the electrical output circuit when the input quantity (excitation quantity) is changed to meet the specified requirements. It has an interactive relationship between the control system (also called input circuit) and the controlled system (also called output circuit). Usually used in automatic control circuits, it is actually an “automatic switch” that uses a small current to control the operation of a large current. Therefore, it plays the role of automatic regulation, safety protection and conversion circuit in the circuit.

2. The main role of relays

Relay is an automatic switching element with isolation function, when the change of excitation in the input circuit reaches the specified value, it can make the output circuit of the controlled power to a predetermined step change in the automatic circuit control device. It has a sensing mechanism to respond to external excitation (electrical or non-electrical), an actuator to control the “on” and “off” of the controlled circuit, and an intermediate comparison mechanism to compare, judge and convert the magnitude of the excitation. Relays are widely used in remote control, telemetry, communication, automatic control, mechatronics, and aerospace technology to control, protect, regulate, and transmit information.

Relays generally have an induction mechanism (input part) that reflects certain input variables (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.); an actuator (output part) that controls the controlled circuit “on” and “off”; and an intermediate mechanism (drive part) that couples and isolates the input quantity, processes the function and drives the output part between the input and output parts. Between the input and output parts of the relay, there is an intermediate mechanism (drive part) that couples and isolates the input, processes the function and drives the output.

As a control element, the relay has several roles.

(1) Expanding the control range: For example, a multi-contact relay control signal up to a certain value can be switched, opened and turned on multiple circuits at the same time according to the different forms of contact groups.

(2) Amplification: For example, sensitive relays, intermediate relays, etc., with a very small amount of control, you can control a very high-power circuit.

(3) Integrated signals: For example, when multiple control signals are fed into a multi-winding relay in a prescribed form, they are compared and integrated to achieve a predetermined control effect.

(4) Automatic, remote control, monitoring: For example, relays on automatic devices, together with other electrical appliances, can form programmed control lines, thus enabling automated operation.