PLC 2 Flashcards
What is floating master?
Processor holds token and gives it to another processor who wants it.
What is token passing?
Token is passed from the lowest node number to next number. Can only hold token limited amount of time.
Data Highway Plus - Up to how many stations can a token passing network have? How is it numbered?
Up to 64 stations, 0 to 77 octal
Data Highway Plus - What cable is built a twisted pair with a shield?
Belden 9463
Data Highway Plus - Cabling may be installed in what two ways?
Daisy chain and trunk line/ drop line
What is the industrial ethernet of siemens?
ProfiNET
Most I/O communications are a slave master relationship; true or false?
False: Most I/O communications are a MASTER SLAVE relationship
How does master slave operation work?
- The PLC or master scans the remote devices for data
- It reads input data and writes output data
What does bit shift do?
Shifts individual bits in an array to the left or right.
What data type must Bit shift use for its array?
DINT
What is the .UL bit in a Bit Shift instruction?
That is the unload bit. This contains the value of the last bit shifted out.
What does the Bit Shift use to load a bit into the array?
Source is the value to be loaded into the array
What happens to the rest of the bits in an array if you are only shifted 7 bits?
It ignores the rest because you only chose to shift 7 bits
You want to copy an array to another array, what instruction should you use?
COP (copy instruction) or FAL instruction
Parts are being loaded into a warehouse bay each one has a unique
serial number associated with it. What instruction can I use to keep
track of these parts?
LIFO unload (LAST IN FIRST OUT)
A conveyor belt has a number of stations. I need to keep track of which stations have parts at them as the conveyor belt moves. What instruction can I use to keep track of these parts?
BIT SHIFT!
What instruction allows PLCs to read/write to/from each other?
Message Instruction (MSG)
What is the data type of a MESSAGE instruction?
Message Control Tag
Can you using the same MESSAGE tags for more than one MSG instruction?
No
In the configuration tab of the message instruction - If reading from a plc what should you put in the source element?
The target PLC tag you want to read which is usually an array
In the communication tab of the message instruction - What goes in the path option?
The necessary information for the PLC to connect to the target PLC
When talking to ControlLogix to ControlLogix, what does this mean:
LocalENB, 2, 192.168.1.30, 1, 0
◦ LocalENB is the name of your Ethernet Card
◦ 2 indicates Ethernet/IP
◦ 192.168.1.30 is the IP address of the other PLC
◦ 1 indicates communications across the backplane
◦ 0 indicates the slot of the processor
When talking to ControlLogix to CompactLogix, what does this mean:
LocalENB, 2, 192.168.1.30
◦ LocalENB is the name of your Ethernet Card
◦ 2 indicates Ethernet/IP
◦ 192.168.1.30 is the IP address of the other PLC
When talking to CompactLogix to CompactLogix, what does this mean:
2, 192.168.1.30
◦ 2 indicates Ethernet/IP
◦ 192.168.1.30 is the IP address of the other PLC
True or false: A msg instruction needs the rung to be true to execute instruction?
True
How would you know if a MSG instruction is successful?
The .DN bit will activate
How would you know if a MSG instruction failed?
The .ER bit will activate
Where can you find the error information of the MSG instruction?
Go into the configuration box, you will see it in the bottom
How many connections are made with a MSG instruction?
1
What are the 5 programming languages for PLCs
*Ladder Diagram (LD)
*Function Block Diagram (FBD)
*Structured Text (ST)
*Instruction List (IL)
*Sequential Function Chart (SFC)
How do you get inputs and outputs in Function Block Diagram?
Using input reference and output reference
What is the datatype of a timer in Function Block Diagram?
FBD_Timer
What is Sequencial Function Charts?
*It’s a flow chart, but you get to control equipment with it
*Made up of steps and transitions
*The program will stay on a step until the next transition becomes true
*Then it moves on to the next step
*Most likely to be used when your application goes through a series of
steps before starting over again (e.g. an automation cell has a part
placed in it, then is clamped down, then is welded, then unclamped,
then removed, then the process starts over)
In SFC, what does the step instruction do?
The step is responsible for ordering any actions
In SFC, what does the transition instruction do?
When the conditions in transition become true, we move to the next step
In SFC, what is in the action instruction of the step instruction?
What we want to do in the in that step
How do VFDs control speed?
*AC drives vary the frequency applied to a 3 phase AC motor
*Vary the frequency and you vary the speed
*Voltage must also be varied or the motor will be destroyed (it will cook)
True or false: 99.99% of AC drives use PWM due to its efficiency
True
What options do you have in controlling an AC drive frequency?
Drive frequency may also be controlled by:
◦ A 0 – 10V signal from an analog output card
◦ A 4 – 20 mA signal
◦ Selector switches that select preset frequencies
What can an HMI offer?
*Soft pushbuttons (normally open, normally closed, maintained – push
on/push off)
*Soft pilot lamps
*Numeric data displays
*Numeric input objects (with floating keypads)
What is an I/O List?
*A list that details what cards/modules are in each slot of the chassis
*Also details what is wired to each point/channel of each card
Why use an I/O List?
*Makes programming easier
*A reference for troubleshooting
*Document that is used by multiple people (programmers, engineers,
electricians)
What is a Sequencer?
*An organized way of stepping through a sequence of events
*At each step we can turn on/off any number of outputs
*This can greatly simplify our logic but requires some planning
How to make SQO work
- Make array of DINTS
- Map individual elements in the array for conditions need (ex. 1010)
-Put the array in the source
-Use a subnet mask so that it will only see those 4 bits and ignore the rest
-Destination bit will be used as the input. It will have those mapped bits depending on which sequences its on
What does SQI do?
Compares bits from a source and an array and if they are the same it will send a 1
