Controls › Control Panels
PLC Panels
The control section of a panel around a programmable controller.
Written guides in this section
Full references, procedures, and diagnostic guides published under PLC Panels.
PLC Power
Powering the controller section of a panel: the control transformer and 24 volt supplies, separating controller power from field I/O power, sizing with margin, the UPS and what rides through, protection and monitoring, the DC ground, and restart sequencing.
8 min readUpdated Sep 5, 2026
Panel I/O
Arranging the I/O in a controller panel: module types for the field devices, sinking, sourcing, and isolated inputs, fused and relay outputs, the path from field terminal to module, spare capacity, and addressing that follows the I/O list.
8 min readUpdated Sep 5, 2026
Relays in the PLC Panel
The relays a controller panel needs and why: interposing relays between outputs and loads, input relays for high-voltage and remote signals, isolation and safety relays, monitoring relays, coil and contact selection, and keeping logic out of relays.
7 min readUpdated Sep 5, 2026
Isolation
Isolating the controller from the field: why grounds differ and what that does to signals, signal isolators and isolated channels, isolation transformers and their limits, relays as isolation, fiber as the ultimate isolator, and when isolation is worth it.
8 min readUpdated Sep 5, 2026
Panel Surge Protection
Surge protection of a controller panel as a system: a single entrance and the ground bar it lands on, staged protection on the power, protectors on every loop and data line that leaves the building, the radio feed, layout, and the checklist after a strike.
8 min readUpdated Sep 5, 2026
Panel Networking
The network inside a controller panel: which networks exist and how they are kept apart, where the switch sits, copper patching and fiber entry, the radio or cellular router as a panel component, cable management, shield grounding, and labeling.
7 min readUpdated Sep 5, 2026
Topics in this area
PLC Power
PLC Power — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Panel I/O
Panel I/O — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Relays
Relays — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Isolation
Isolation — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Panel Surge Protection
Panel Surge Protection — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Panel Networking
Panel Networking — practical reference notes for controls engineers, integrators, and technicians working with plc panels.
Direct contact
Have a controls question?
Reach Eric Sullivan directly about anything on this site, a controls or automation topic, or one of his personal projects.
References to manufacturers, products, model numbers, software platforms, technical specifications, companies, standards organizations, or other organizations are provided for informational purposes and do not imply sponsorship, endorsement, authorization, or affiliation unless expressly stated. Manufacturer specifications must be independently verified against current manufacturer documentation.