Relays are electromechanical or electronic switches that open and shut circuits. Relays operate one electrical circuit by opening and shutting contacts in another. When a relay contact is usually open (NO), there is an open contact when the relay is not activated, as seen in relay schematics. When the relay contact is normally closed (NC), there is a closed contact when the relay is not activated.
The simplest type of relay is a mechanical switch with two contacts, one for each phase. When you turn a knob or push a button on this type of relay, it opens or closes these contacts. These simple relays were used extensively in early radio and television sets to control lamps, motors, and other devices that were not powered directly from the line voltage.
Electromagnetic relays are similar to mechanical relays but use magnetic forces instead of physical levers to connect or disconnect circuits. This type of relay is used in place of mechanical switches for applications where vibration or movement must be prevented during switching operations.
Solid-state relays use semiconductor components such as transistors to replace some or all of the electromechanical parts in a relay. These relays are more reliable than their mechanical counterparts and can also handle higher current loads. They are used in many low-voltage applications such as home appliances and industrial machinery.
The term "relay" may also refer to the act of opening or closing contacts.
A relay is essentially a device with contacts that opens and shuts a switch in response to an input signal (voltage or current) delivered to a coil. Relays can be divided into two types: mechanical relays and solid-state relays. Mechanical relays are still used in some low-speed applications such as power on/off switches, but they are being replaced by solid-state devices in most other applications.
Solid-state relays use semiconductor components instead of electromechanical parts. They are more reliable and require less maintenance than their mechanical counterparts. Also, SSRs can handle higher voltages and currents than mechanical relays. Their main disadvantage is that they cannot be switched "on" or "off" like a mechanical relay; rather, they must be programmed to either the "on" or "off" position. This is not a problem for many applications where the relay will only be on or off for a short period of time (such as when lighting up an indicator lamp). However, if you need to control something that requires continuous communication with the line, then an SSR is not suitable. Also, SSRs are much more expensive than mechanical relays.
Electromagnetic relays are similar to electrical switches but they use magnetic forces instead of electrical circuits to operate them. These devices were commonly used in early computers because they needed simple on/off switching ability at relatively high voltage levels.
A relay is a switch that is powered by electricity. It has a set of input terminals for a single or many control signals, as well as a set of operational contact terminals. The switch may contain an unlimited number of contacts in various contact types, such as make contacts, break contacts, or combinations of the two. A relay can be controlled either directly or indirectly via another device such as a transistor.
Relays were originally used in radio and television sets to enable or disable parts of the system during testing or maintenance. Today they are used in virtually all devices with a on/off requirement where a simple circuit cannot be used because it would always turn off when not needed. This category includes lights, appliances, and equipment ranging from small lamps to large generators. Relays can also be found in computer peripherals such as printers, scanners, and cable modems. They are even used as replacements for mechanical switches in certain applications!
The term "relay" comes from the old name for a magnetic switch, which was called a "receiver". These early radios used magnetic switches to connect audio sources (such as microphones) to speakers (for example).
In modern technology, relays are usually made from semiconductor materials; however, they work on the same principle as their older mechanical counterparts. Semiconductor relays have advantages over mechanical switches because they are less likely to experience wear-and-tear damage and malfunction over time.