Where used in a control circuit, relay coils are connected to the ___ terminals on a programmable controller.

Where used in a control circuit, relay coils are connected to the ___ terminals on a programmable controller.

• A. Input
• B. Output
• C. Controller
• D. None of these

Answer: (B)

In a PLC-based control circuit, devices like relay coils are considered the loads that the controller powers to produce action. The coil needs a controlled source of voltage/current, which is provided by the PLC’s output terminals. The outputs are specifically designed to switch external loads on and off under program control, so connecting the relay coil to the output terminals allows the PLC to energize or de-energize the coil as needed. Input terminals are for sensing signals from field devices (like sensors or switches) and do not supply load power. The controller refers to the PLC’s central processing unit, not a terminal type. None of these would be appropriate because there is a proper place for a coil to be driven: the output terminals.

In a PLC-based control circuit, devices like relay coils are considered the loads that the controller powers to produce action. The coil needs a controlled source of voltage/current, which is provided by the PLC’s output terminals. The outputs are specifically designed to switch external loads on and off under program control, so connecting the relay coil to the output terminals allows the PLC to energize or de-energize the coil as needed.

Input terminals are for sensing signals from field devices (like sensors or switches) and do not supply load power. The controller refers to the PLC’s central processing unit, not a terminal type. None of these would be appropriate because there is a proper place for a coil to be driven: the output terminals.