08-09-2016, 10:23 AM
1453714603-IntrotoPLCs.pdf (Size: 2.14 MB / Downloads: 39)
The Need for PLCs
• Hardwired panels were very time consuming
to wire, debug and change.
• GM identified the following requirements for
computer controllers to replace hardwired
panels.
– Solid-state not mechanical
– Easy to modify input and output devices
– Easily programmed and maintained by plant
electricians
– Be able to function in an industrial environment
The First Programmable Logic
Controllers (PLCs)
• Introduced in the late 1960’s
• Developed to offer the same functionality as
the existing relay logic systems
• Programmable, reusable and reliable
–
Could withstand a harsh industrial environment
They had no hard drive, they had battery backup
Could start in seconds
Used Ladder Logic for programming