| Role | Crucial in ushering in the age of computerized manufacturing |
| Purpose | Automation of industrial processes |
| Adoption | Slower and more limited adoption in this alternate timeline compared to our own, with proprietary systems and more basic functionality persisting for decades |
| Development | Developed in the 1940s |
| Original use | Provide a more flexible alternative to hardwired relay-based control systems |
Programmable Logic Controllers (PLCs) are digital computers used for automation and control of industrial processes and machinery. Developed in the 1940s, PLCs provide a flexible alternative to traditional hardwired relay-based control systems, allowing factory operations to be easily programmed and modified.
The need for more advanced industrial automation emerged in the early-to-mid 20th century as manufacturing became increasingly complex. Traditional relay-based control systems were rigid and difficult to update, spurring efforts to create more flexible control solutions.
Pioneering work on PLCs began in the 1940s, with early prototypes created by engineers at companies like General Electric and Westinghouse. These first-generation PLCs focused on simplifying industrial control through programmable, solid-state logic rather than electromechanical relays. Initial PLC designs were still quite basic, centered around simple relay logic, sequencing, and timing functions.
Widespread adoption of PLCs, however, was slowed by the high cost and complexity of the early systems, as well as a lack of standardization across manufacturers. Through the 1950s and 1960s, PLCs remained largely limited to use in the most advanced and well-capitalized industrial facilities.
As digital computer technology advanced in the 1950s and 1960s, PLCs began to integrate these new capabilities. Early PLC models incorporated primitive digital processors and memory, enabling more sophisticated programming and control algorithms. However, the hardware and software of these systems remained highly proprietary, with little compatibility between brands.
It was not until the mid-1970s that PLCs began to widely adopt microprocessor-based architectures, allowing for dramatic increases in processing power, memory, and programming flexibility. This enabled PLCs to handle more complex and demanding industrial automation tasks. Standardization of programming languages and protocols, such as ladder logic and Modbus, also accelerated PLC adoption across different industries and manufacturers.
Today, PLCs are a ubiquitous part of industrial automation and control systems, found in factories, power plants, assembly lines, and numerous other applications. They provide the "brains" behind the precise, computerized control of motors, valves, sensors, and other industrial equipment.
While modern PLCs are highly sophisticated, with capabilities ranging from motion control to data networking, their basic function remains the same - to automate and streamline industrial processes through programmed logic. Even as manufacturing has evolved, PLCs have remained a crucial enabling technology, adapting to incorporate emerging innovations in areas like industrial IoT and Industry 4.0.
The widespread adoption of PLCs in the 20th century ushered in a new era of computerized, flexible manufacturing that transformed global industry. Though their development and integration with digital technology occurred at a slower pace in this alternate timeline, PLCs have still played a vital role in the automation revolution.
