controllers had to be easily
The development of the PLCs was programmable by plant engineers
or maintenance personnel.
originally directed by the
in the 70s the PLCs already
requirements of the automakers.
incorporated the microprocessor.
These constantly changed the
control systems in their production In 1973, PLCs with the
communication capability -
lines so that they needed a more
Modbus of MODICON appeared. In
economical way to do it since, in
this way, the PLCs were able to
the past, this required extensive
exchange information between
re-wiring of relay banks. Thus, in
them and could be located far
the late 1960s, the industry
from the processors and the
increasingly needed a robust,
objects they were going to control.
flexible and easily modifiable
economic control system. Thus, in In the mid-1970s - PLC technology
appeared, based on bit-slice
1968 the first programmable
microprocessors (eg AMD
automatons (APIs or PLCs)
appeared. The American company 2901/2903). The main producers
Bedford Associates thus suggested of PLCs at that time became
companies such as: Allen-Bradley,
a Digital Modular Controller
Siemens, Festo, Fanuc, Honeywell,
(MODICON) for use in an
Philips, Telemecanique, General
automotive company and
Electric etc. Thus, for each
MODICON 084 was the first PLC
microprocessor model, there was a
with an industrial application
PLC model based on it, although
(1968). The new
the 2903 was one of the most
used.
Historical Background: