What will be used before the control of PLC and SCADA?

What will be Used Before the Control of PLC and SCADA?

In the realm of industrial automation, the evolution of technology has paved the way for sophisticated systems like Programmable Logic Controllers (PLCs) and Supervisory Control and Data Acquisition (SCADA). But before these powerful tools came into play, there were foundational technologies that laid the groundwork for automation as we know it today. In this article, we’ll delve into the tools and systems that preceded PLCs and SCADA, shaping the landscape of industrial control.

1. Relays and Timers:

Before PLCs revolutionized industrial control, relays and timers were the backbone of automation. Relays acted as switches, allowing control signals to manage the operation of machinery and processes. Timers, on the other hand, provided the ability to introduce time delays and sequences into control circuits. While effective, these systems were limited in functionality and scalability compared to modern PLCs.

2. Hardwired Control Systems:

Early industrial automation relied heavily on hardwired control systems, where electrical circuits were physically interconnected to perform specific tasks. These systems were cumbersome to design and modify since any changes required rewiring of components. Despite their limitations, hardwired systems were instrumental in automating simple, repetitive tasks in manufacturing environments.

3. Pneumatic and Hydraulic Controls:

In addition to electrical control systems, pneumatic and hydraulic controls played a crucial role in industrial automation. These systems utilized compressed air or fluid pressure to actuate valves, cylinders, and other mechanical components. While effective for certain applications, pneumatic and hydraulic controls lacked the flexibility and precision offered by electronic control systems like PLCs.

4. Analog Control Systems:

Analog control systems were prevalent before the widespread adoption of digital technologies. These systems utilized continuous signals to regulate processes, with components such as potentiometers and analog amplifiers playing key roles. While analog control provided smooth and precise regulation, it was susceptible to noise and environmental interference, limiting its reliability in industrial settings.

5. Manual Control Panels:

Before the advent of automated control systems, manual control panels were commonplace in industrial facilities. Operators manually adjusted switches, knobs, and levers to regulate machinery and processes. While simple and intuitive, manual control panels were prone to human error and lacked the efficiency and consistency offered by automated systems.

6. Relay Logic Control Systems:

Relay logic control systems represented a significant advancement in industrial automation before the introduction of PLCs. These systems utilized relay-based circuits to implement control logic, allowing for more complex sequences and interlocks. While an improvement over hardwired control, relay logic systems were still limited by the physical constraints of relay technology.

7. Distributed Control Systems (DCS):

In certain industries, distributed control systems emerged as a precursor to SCADA systems. DCS decentralized control functions across multiple nodes or controllers, allowing for greater flexibility and redundancy. However, DCS lacked the comprehensive data acquisition and visualization capabilities that would later define SCADA systems.

8. Process Control Computers:

Before the integration of SCADA systems, process control computers were used to monitor and control industrial processes. These early computers provided rudimentary data logging and analysis capabilities, but lacked the real-time monitoring and remote access features of modern SCADA systems.


Before the rise of PLCs and SCADA systems, industrial automation relied on a variety of tools and technologies to achieve control and optimization. From relays and timers to manual control panels and process control computers, each of these predecessors played a vital role in shaping the evolution of automation. While they may seem primitive by today’s standards, these foundational systems laid the groundwork for the advanced control systems that drive modern industry. As we continue to innovate and advance, it’s essential to recognize the contributions of these early technologies to the field of industrial automation.

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