Plc Flashcards
Where and what kind of field were plcs first used and what were they called
GM
Automotive
Modicon
Plcs are programmed using ____________ ladder __________.
Relay ladder logic
Plcs can typically run _____________ programs at a time
One
T/F relay ladder logic is the same as motor control ladder schematics.
False
Plcs also include communications for _____________/_________/________________.
Internet/wifi/programming devices
What are the basic parts of a Plc.
-input module
-isolations
-cpu
-power supply (battery backup?)
-programming device
-output module
What could a programming device be?
-remote
-pc
-laptop
-phone?
-programming pack
What kind of isolators are typically used in plcs
Opto-isolators
T/F there is electrical connection between input module-cpu-output module
False
Advantages of a Plc
-robust power
-reliable in high electric noise areas
-lots of various I/I voltage combinations
-low power pilot devices like pb’s and limit sw
-led indicators on input and output modules
-work in wide range of temperatures
-reduced use of electromechanical relays.
Memory structure of a Plc
Executive
Scratch pad
Data tables
User program
Which parts of the memory structure are part of the system memory (firmware like bios)
Executive
Scratch pad
Which parts of the memory structure is part of the application memory
Data tables
User program
One word equals ___ bits
16
___ bits make a byte
8
___ bits make a nibble
4
Data tables includes what?
Bits
Timers
Counters
Input image
Output image
Scanning includes
Reading inputs
Executing program
Updating outputs
Scan time depends on what
Number of inputs and outputs
Program length
Types of instructions
In a block from how does the scanning process look
Read input image table
Solve program logic
Update output image table
Scan time in the 1990’s was around
______msec
100
Scan time in the 2000’s was ______msec
20
Scan time in the 2010’s ______msec
5-20
Scan time in the 2020’s was improved to about _______msec
1-20
Inputs can be ___________ which means on/off
Descreet
What is another word for a discreet input
Digital
Inputs can be ______ or _____
Ac or DC
Common input voltages are
24vac, 24vdc, 10-60vdc, 5vdc 120vac etc
Inputs can also be ___________ which is variable
Analog
Common variable input values are
4-20mA, 1-5vdc, 0-10vdc etc
Analog input modules have a __________ to ____________ converter and give a __________ value out.
Analog to digital
Binary
Outputs are usually ______________
Discreet or digital
Outputs can be _____ or ______ or ___________ outputs
Ac
DC
Relay outputs
Relay outputs are also known as ____________ or ___________
Potential free or dry contacts
Ac outputs typically use a ___________ for switching
Triac
Triac (AC) have about a ____A max
2
Triac outputs have a small ________________ when off, which may activate small high impedance output devices. Why is this bad?
Leakage current
It’s dangerous(could be voltage when not expected )
_______________ relays or ____________ resistor can be used to prevent the leakage current in a triac output
Interposing
Burden
Analog output modules use a ____________ to ____________ converter to convert a _____________ value into a 4-20mA, 1-5vdc etc signal
Digital to analog (DAC)
Binary
1 word is 2^15 which would have ______________ distinct levels
32,768
If current is flowing from a switch to the output device:
The switch is ______________
The output is ______________
Sourcing
Sinking
If current is flowing from the output device to a switch then:
The switch is. _______________
And the output is _______________
Sinking
Sourcing
——–] [———– this is a?
Examine if on instruction
—–]/[—– this is a?
Examine if off instruction
An examine if on instruction is looking for a ___ if it has one the instruction will be ______
1
True
An examine if off instruction is looking for a ___ if it has one the instruction is ______
0
True
Plc logic scans from ________ to ________
And _________ to ___________.
Left to right
Top to bottom
—–( )—– this is a?
Out put instruction
What are these called
I:0.0/00
^^ ^ ^
12 3 4
1 input
#2 slot #
#3 word#
#4 bit#
An internal bit is essentially a ___________ coil
Virtual
Internal bits are _____________
Registers ( little memory places)
Internal bits are used for ____________
One shots
Internal bits are updated ___________ the logic and not _______________
During
At the end of scan
Internal bits will be on ________________ scan.
Every other
What instruction will set an output on even if the logic in the rung becomes false
Latch
What instruction remains true even in the even of a power outage
Latch
A latched output will only become false when the ____________ is true
The unlatch output
A _______ is an input instruction that will be true for one scan only.
Osr
Osr stand for
One shot rising
When the prior input instructions are true the osr will be true for __________________.
One scan only
An osr is placed in a ring after other _________________________.
Trigger input instructions
The output instruction of an osr will only be true for the ______________________.
Duration of the scan
Applications of an osr
Incrementing speed of a motor equally with one press of a button
Capturing a fast computer which otherwise would be unreadable
Fusing for a plcs output must be _____________
External
If you needed to switch a load with a voltage higher than the output voltage of the Plc what would you use
Interposing relay
What are the different kind of power supply that can be applied to a Plc from okay to best (5)
Raw power
Isolating transformer
Voltage regulating transformer
Conditioned power
Uninterruptible power supply
______________ voltages have less effect on current type inputs
Transient
______________ input wiring for sensors reduces I’ll effects of EMI and RFI
Shielded
For shielded input wiring the bonding must be only __________________
Connected on one end of the shield
________________ is critical for sensitive signals
Good bonding
_______________ uses very large conductors
Brute force
A _____________ retains the accumulated value when the timer is done
RTO
A RTO must have a __________ instruction addressed to it
Reset
Applications for an RTO
Track the running time of a motor for maintenance
Runtime counter for a back up generator
A counter or timer reset is not used for which kind
TOF
OV is when
But=1
When accumulated is greater than preset
In is when
Bit=1
When accumulated is less than ∅
Input devices for fail safe operation should not be wired ________ they should be ______ or in some cases ___________
No
Nc
Nohc
A twisted conductor will have _____ the voltage on each conductor
1/2
A locap conductor with a line and a return is considered
Unbalanced
