1. What is a relay?
A relay is an electrically operated toggle switch. Specialized for switching large currents that control circuit systems cannot directly interfere. People will use relays to switch high currents.
The relay device has 2 states ON and OFF. The relay is in the ON or OFF state depending on whether current flows through the relay or not. Besides, it comes in many different shapes and sizes and pins.
2.Structure and Working principle of Relay
Structure of the Relay
Relays are composed of basic parts such as electromagnets, drive levers and input and output terminals.
When a current flows through the electromagnet coil, the mechanical energy changes the output circuit from the closed port to the open one. And the switch bars can be fitted with spring levers to make the switching process happen definitively.
Working principle of Relay
When a current flows through the relay and through the coil inside and creates an attractive magnetic field. This magnetic field acts on a lever to open or close the electrical contacts and thus change the state of the relay. The number of electrical contacts changed can be 1 or more, depending on the design.
The relay has 2 independent circuits that operate. One circuit is to control the coil of a relay: It controls the relay to be ON or OFF. A current control circuit we need to control whether through the relay or not based on the ON or OFF state of the relay.
On the relay there are 3 symbols: “NO, NC and COM”. In there:
- COM: is a common pin, it is always connected to 1 of the other 2 pins. As for which pin it is connected to, it depends on the operating state of the relay.
- NC: That means it’s normally closed. That is, when the relay is in the OFF state, the COM pin will be connected to this pin.
- NO: When the relay is in the ON state (with current flowing through the coil), the COM pin will be connected to this pin.
>>> Connect the COM and NC when you want to have the joystick current when the relay is in the OFF state. And when the relay is ON, this current is cut off. Otherwise, connect COM and NO.
Applications of Relay
Relays are used to divide signals to many other parts in the control circuit diagram system. Not only that, the relay is also an output element and can isolate the voltage between the actuators such as AC, high voltage with the control part to transmit the signal to the rear part.
In addition, relays are widely used in industries and daily life by their automation and monitoring of safety systems. Or used to cut off power to machinery to ensure safety.
