PLC and SCADA are the two terms you hear most when a factory line gets automated — and they are often confused. This is a guide to physical industrial control systems on a real production line. To be clear up front: this is industrial and factory automation — not consumer or humanoid robotics, robotics education, AI, or RPA (robotic process automation) software. RoboFactory Africa engineers both PLC and SCADA as part of automation systems integration in Ghana and Togo, since 2018.

The Short Answer

A PLC (Programmable Logic Controller) is the controller on the floor that runs the machine logic — reading sensors, driving actuators, executing the control sequence in real time. SCADA (Supervisory Control and Data Acquisition) is the supervisory layer above it — visualising the process, collecting data, raising alarms, and letting operators monitor and adjust the line. They are complementary, not competing.

What a PLC Does

The Real-Time Controller

The PLC is deterministic and fast. It reads inputs (sensors, switches, encoders), executes logic, and writes outputs (motors, valves, robotic-cell handshakes) — cycle after cycle. PLC programming is commonly engineered to IEC 61131-3, the international standard for PLC programming languages.

It Lives on the Floor

A PLC sits in a control panel — itself an assembly engineered to recognised practice such as IEC 61439 — wired into the machinery it controls.

What SCADA Does

The Supervisory & Data Layer

SCADA gives operators a window onto the process: live screens, trends, alarms, and the controls to supervise the line. It collects data from one or many PLCs and presents the plant’s state in one place.

It Is About Visibility and Decisions

Where the PLC decides what the machine does millisecond to millisecond, SCADA is where humans and higher systems see and steer the process.

How They Work Together

On an integrated line, PLCs run the machine-level control and a SCADA layer supervises across the plant. Where production data must reach the MES/ERP, that integration follows ISA-95. Where the control system is exposed to networks, OT cybersecurity practice such as IEC 62443 applies. We describe these as the framework we work to, and claim a specific certification only where it is actually held.

Safety Sits Across Both

Neither PLC nor SCADA replaces a safety case. Machinery and robot-cell safety is risk-assessed to ISO 12100 and ISO 10218-2, and functional-safety / SIL practice (IEC 61508 / IEC 61511) applies where the process demands it — all within Ghana’s factory-safety regime: the Factories, Offices and Shops Act 1970 (Act 328) / DFI, not the GSA.

What It Costs

A PLC/SCADA system is scoped and quoted per project — controller count, I/O, SCADA scope and integration all drive it. There is no flat published rate, and we never quote an invented figure.

Frequently Asked Questions

Is SCADA a replacement for a PLC?

No. The PLC runs the real-time control; SCADA supervises, visualises and collects data above it. A typical integrated line uses both.

Is this the same as RPA software?

No. RPA automates software tasks on computers. PLC and SCADA control physical machinery and processes on a factory floor — this is industrial automation.

Which PLC programming standard do you follow?

We engineer PLC programming to recognised practice including IEC 61131-3, as the framework we work to.

Request a consultation — or scope an automation project: +233 20 531 3333.