Ken Ball for Control Engineering

How Programmable Logic Controllers Emerged from Industry Needs

Programmable logic controllers (PLCs) were more of a technology evolution than a startling discovery. The earliest robust, easily re-programmed industrial controller—which we know as the PLC—evolved nearly concurrently along three independent paths and involved five companies: Bedford Associates; General Motors Hydra-matic Division, Ypsilanti, MI plant; International Instruments Inc.