What is a relay? What is a relay?

Update:20-10-2021
What is called a relay, a relay is an electrical control device, which is an electrical appliance that causes the controlled quantity to undergo a predetermined step change in the electrical output circuit when the input quantity (excitation quantity) changes to the specified requirements. When we use electrical appliances, if we do not have a relay, we cannot complete many actions. The tripping and power-off actions of the relay are very important, so let's take a look at what a relay is.

What is a relay?
A relay is a device that uses the effect of current to close or open a circuit for automatic protection and automatic control. In most cases, the relay is an electromagnet, and the armature of this electromagnet can close or open one or several contact points. When current flows through the winding of the electromagnet, the armature is attracted by the electromagnet, thus changing the state of the contact. The main function of the relay is for signal detection, transmission, conversion or processing. Its on-off circuit current is usually small, that is, it is generally used in the control circuit (compared with the "main circuit").

For example:
1. Relays are used in the automotive field
The more common relays are: starter relays to start motors, horn relays, motor or generator disconnection relays, charging voltage and current adjustment relays, transition signal flashing relays, light brightness control relays, air conditioning control relays, and automatic sliding door opening and closing control Relay; window lift control relay.

2. Relays are used in household appliances
Air conditioning relays are mainly used to control compressor motors, fan motors and cooling pump motors to perform related control functions.

3. Relays are used in industrial control relays
The main control function is completed by the universal AC relay. The relay is usually driven by a button or limit switch. The contacts of the relay can control solenoid valves, larger starting motors, and indicator lights.

Regarding what is called a relay, we can understand that when the input (electricity, magnetism, sound, light, heat) reaches a certain value, the output will be an automatic control device that will change in a jump, then it is a relay.

Classified according to the working principle of the relay:
1. Electromagnetic relay: a kind of electrical relay that uses the suction force generated between the electromagnet core and the armature in the input circuit.
2. Solid state relay: refers to a relay whose input and output are isolated with electronic components performing their functions without mechanical moving parts.
3. Temperature relay: a relay that acts when the outside temperature reaches a given value.
4. Reed relay: a relay that uses the reed action sealed in the tube and has the dual functions of the electric shock reed and the armature magnetic circuit to open, close or switch the circuit
5. Time relay: When the input signal is added or removed, the output part needs to be delayed or time-limited before closing or disconnecting the controlled circuit relay until the specified time.
6. High-frequency relay: A relay with minimal loss for switching high-frequency and radio-frequency circuits.
7. Polarized relay: a relay that has a combined action of polarized magnetic field and control current through the magnetic field generated by the control coil. The operating direction of the relay depends on the direction of the current flowing in the control coil.

Other types of relays: such as optical relays, acoustic relays, thermal relays, instrument relays, Hall effect relays, differential relays, etc. The action mode of the relay is basically the same, it will automatically close or open after reaching a certain condition.