LinuxPlanet: Automating Manufacturing Processes with Ethernet-Enabled I/O Modules, Linux

“Traditional control of industrial processes has been carried
out by small special purpose-built microprocessor based systems
called PLCs, also known as programmable logic controllers. They
have very fast cycle times and essentially run in an endless loop
looking at inputs, making decisions and controlling outputs. PLCs
are programmed with an industry standard language known as ladder
logic. They can respond, in real time, to hundreds of inputs and
can control all types of motors, relays and actuators. PLCs are the
quick thinking brains of the industrial automation world.

“As the old hot rodding saying goes, ‘Speed costs money, how
fast do you want to spend?’ PLC systems are plenty fast and plenty
pricey. In the case of PLCs all that speed also needs to be
protected from the industrial environment. The control computer
(PLC) and I/O modules have always been located physically near the
industrial machine in a metal cabinet, right out there on the shop
floor. Putting the cabinet next to the machine being controlled
made sense because all the switches, sensors, motors and relays had
to be connected by heavy wires back to the I/O modules…”

Complete
Story