J4 PLC Flashcards
List the four elements of a PLC
Input section
CPU section
Programming device
Output section
Describe the input section of a PLC
designed to sense the state of the field devices that are wired to the input terminals.
Describe the CPU section
is the “brain” of the PLC
has a battery to support essential parts of the volatile memory
Describe the Output section
provides power to loads
loads must be in the range of about 10 A
Program entry
can be accomplish on the screen of the PLC or with an external PC and PLC software
Documentation
text descriptions for ladder diagrams
Run Mode
gives the PLC the go ahead to solve the program
Monitoring
PC monitors the PLC ladder diagram in real time.
Used for trouble shooting
What is an intelligent terminal?
will allow a PLC program to be developed without being connected to the PLC itself
What is a dumb terminal?
on that must be connected to the PLC to operate it has no stand alone capabilities.
Hand-held programmers
are a type of dedicated terminal
rugged
Advantages of a PLC
Reliability Flexibility Expandability Accuracy Ease of installation Maintainability
describe a byte
it is 8 bits
whats a bit
one piece of information such as a 0 or a 1
describe 16 bit
it is a 2 byte word
a 16 bit machine can process
2 bytes at a time
Executive memory
never changes and is stored on a some type of non-volatile memory
all input and outputs must be
addressed properly for the CPU to be able to process them.
a Discrete input
has only two states on or off
DC input modules (sink/source)
sink: positive is switched in the field and the input goes positive
source: negative is switched in the field and the input goes negative
Grounding and shielding
shields must be grounded at one point only
Master control relay
for safety
shuts of power to all inputs and outputs
List three items on which the scan time depends on
speed of the CPU
Length of program
Number of I/O
What is required to capture high-speed switching events
interrupts
