Chapter 1 Flashcards
1
Q
What is a PLC
A
Industrial grade computer that is capable of being programmed to perform control functions
2
Q
Other names for PLC
A
PEC = programmable electronic controllers PC = programmable controller
3
Q
What does PLC mean
A
Programmable Logic Controller
4
Q
Advantages of PLC
A
- increased reliability
- more flexibility (change program instead of rewiring)
- if # of relays needed is greater/equal to 6, PLC is cheaper
- communication capability
- faster response times
- easier to troubleshoot
- easier to test field devices
5
Q
Parts of a PLC
A
- CPU (central processing unit = brain, microprocessor)
- input/output (I/O) section
- power supply
- programming device
6
Q
Open/closed architecture
A
- open: system can be connected easily to devices/programs made by other companies
- closed: harder to connect with other systems (proprietary)
7
Q
Inputs
A
push button, limit switch, pressure switch, proximity switch, photo eyes
8
Q
Outputs
A
lights, horn, solenoids, motor, starter, coil
9
Q
HMI
A
human machine interface
10
Q
PAC
A
- programmable automation controller
- blends advantages of PLC style control with that of PC based systems
11
Q
Fixed vs Modular I/O
A
- fixed: fixed number of connections built in for inputs/outputs (cheaper)
- modular: has expansion capabilities (more flexible)
12
Q
Programming Languages for PLC
A
- relay ladder logic (most common)
- instruction list (IL)
- structured text
- function block diagram (FBD)
- flow charting methods (Grafcet)
13
Q
Scan
A
reads inputs, executes program rung by rung, updates outputs, checks communications
14
Q
Scan time
A
- time required for one full cycle
- depends on how difficult the program is
15
Q
PLC
A
- most common control program
- more versatile than hardwire, can have as many contacts and coils as you want
