Relay Modules

Relays are switches that open and close circuits. They control one electrical circuit by opening or closing contacts in another circuit. When a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is normally closed (NC), there is a closed contact when the relay is not energized. Applying electrical current to the contacts will change their state. Many relays use an electromagnet to mechanically operate a switch, but other operating principles such as solid-state relays are also used. Relays are used where it is necessary to control a circuit by a low-power signal or where several circuits must be controlled by one signal. Depending on the structural features and operating principle, relays are of different types such as monitoring, regulating, auxiliary and protective. Classification of the types of relays depend on the function for which they are used.

Relay modules contain components that make switching and connecting easier, and act as indictors to show if the module is powered and if the relay is active. On the input side of a standard single-channel relay module, is the screw terminal block. This is the part of the module that comes in contact with the mains, and screw terminals make it easier to connect thick mains cables. The three connections on the terminal block are connected to the normally open, normally closed and common terminals of the relay. An input jumper is used to supply power to the relay coil and the ‘relay status LED.’ The output connectors are wires that are suitable for hardware connection.

PLC logic relays combine logic, interface and field connections. They have a modular design with a variety of relay modules enabling channel-specific configurations, and sensors and actuators that can be connected directly to the relay. In addition to the basic module, extension modules can be added for more complex tasks. Up to 48 IO signals can be acquired with a basic module and two extension modules. Parameter adjustments and monitoring can be accomplished using an app for IOS and Android.