The continuous development of science and technology, increasing
demands of the production process, electrical control technology has
evolved from manual to automatic, from simple to complex, from single
to multi-function, changes from hardware control software of control
and efforts. 19 century to the beginning of the early 20th century for
the production of machinery and electric drive. With the continuous
evolution of dragging, electric drive control also undergo constant
change, from the manual step by step to control direction. In the 1960
of the 20th century there was a sequential controller, this logical
component plug control systems, programming simple, greatly reducing
cost, however it is still a means of hardware, and relatively large size.
In the 1970 of the 20th century-a new industrial
controllers-programmable logic controller (PLC) was, with
micro-processing technology as the core, integrated computer technology,
control technology and communication technology, software means to
implement features control, with high anti-jamming ability, suitable
for all kinds of bad environment, combines the advantages of computer
and relays control in two ways.
Transforms the workshop with PLC the old engine bed in the existing
enterprise is the extremely realistic technological transformations
plan, has the investment province, effective quick characteristic.After
uses PLC to transform this engine bed electrical system, has removed
the original engine bed intermediate relay, the time relay, the smooth
diode and the resistance, causes the line to simplify.
Keywords: PLC hardware software relays
