What are the basics of an electrical relay?
- Types and Classification
- Structure and Operating Principles
- Characteristics and Mechanism
Electrical Relay Definition
Relays are electrically operated switches that open and close the circuits by receiving electrical signals from outside sources. Some people may associate “relay” with a racing competition where members of the team take turns passing batons to complete the race.
The “relays” embedded in electrical products work in a similar way; they receive an electrical signal and send the signal to other equipment by turning the switch on and off.
For example, when you push the button on a TV remote to watch TV, it sends an electrical signal to the “relay” inside the TV, turning the main power ON. There are various types of relays used in many applications to control different amounts of currents and number of circuits.
Electrical Relay Types and Classification
- Movable contacts
( Mechanical Relay )
This type of relay has contacts that are mechanically actuated to open/close by a magnetic force to switch signals, currents and voltages ON or OFF.
- No movable contacts
( MOS FET relay, Solid State Relay )
Unlike mechanical relays, this type of relay has no moving contacts but instead employs semiconductor and electrical switching elements such as triac and MOS FET. By the operation of these electronic circuits, signals, currents and voltages are switched ON or OFF electronically.
Electrical relay Structure and Operating Principles
2. MOS FET Relay
- Basic structure of MOS FET relays
MOS FET relay is a semiconductor relay that uses power MOS FETs in output elements.
MOS FET relay consists of the following three components:
- LED ( light-emitting diode ) chip
- PDA ( photodiode array ) chip
* Photodiode Array ( solar cell + control circuit )
- MOS FET chip
* Metal Oxide Semiconductor Field Effect Transistor ( metal, oxide, semiconductor, field, effect, transistor )
- Operating principles of MOS FET relays
MOS FET relays operate according to the following principles.
Electrical relay Characteristics and Mechanism
2. The Three Actions of Electrical Relays
- 1. The relay permits a small amount of electrical current to control high current loads.
When voltage is supplied to the coil, small current passes through the coil, resulting in a larger amount of current passing through the contacts to control the electrical load.
- 2. The relay sends different types of electrical signals.
AC loads can also be electrically controlled (Switching) from DC power source.
- 3. The relay drives multiple outputs with only one input .
One input signal to the coil can simultaneously control several independent circuits (switched).