In a relay output, how are the terminals typically wired?

In a relay output, how are the terminals typically wired?

• A. Both terminals to PLC.
• B. One terminal to the output device, and the other to the power source.
• C. Both terminals to the device.
• D. One terminal to ground, the other to PLC.

Answer: (B)

Relays act as switches that control power to a load. In a typical relay output, the power path is broken by the relay contacts, so the device gets power only when the relay closes. One terminal is connected to the output device and the other to the power source. When the PLC energizes the coil, the contact closes and current flows from the power source through the relay to the device, completing the circuit. Wiring both terminals to the device or both to the PLC wouldn’t provide a proper power path or would bypass the switching function.

Relays act as switches that control power to a load. In a typical relay output, the power path is broken by the relay contacts, so the device gets power only when the relay closes. One terminal is connected to the output device and the other to the power source. When the PLC energizes the coil, the contact closes and current flows from the power source through the relay to the device, completing the circuit. Wiring both terminals to the device or both to the PLC wouldn’t provide a proper power path or would bypass the switching function.