Relay

How it is used

Found in every control cabinet, often to let a PLC output switch a load or to separate voltages. You talk about the coil, NO and NC contacts, relay outputs and interface relays. Safety relays are special relays that monitor E-stops and guard doors.

Example sentences

1. The PLC output drives a relay, and the relay switches the 230 V lamp.

2. The safety relay won't reset until both E-stop channels are closed.

Common collocations

• relay coil
• relay contacts
• safety relay
• interface relay
• relay output

Related terms

• PLCShort for programmable logic controller: a rugged industrial computer that reads inputs from sensors and switches, runs a control program and drives outputs such as motors, valves and lamps.
• I/OShort for inputs and outputs: the signals a controller receives from sensors and buttons, and the signals it sends to valves, motors, lamps and other devices.
• ladder logicA graphical PLC programming language that looks like an electrical relay diagram, with contacts and coils placed on horizontal lines called rungs between two vertical rails.
• emergency stopA red mushroom-shaped button on a yellow background, or the function behind it, that stops a machine as quickly and safely as possible in a dangerous situation.
• solenoid valveA valve that is opened or switched by an electric coil to control the flow of air or liquid. In pneumatics it sends air to one side of a cylinder or the other.

This word in other fields

The same English word can have a different meaning in another field:

• relay · Electrical & Electronics Engineering

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