1. GE Counters and Order of Operation
MAIN 222
Industrial Controllers
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2. Introduction Program Execution See the sheet on Program Execution
The PLC writes inputs to register then drives outputs
Per each rung usually
Sequence is very important
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3. Program Execution In class activity Order of Operations
What is the difference between the programs?
Which one is the one shot?
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4. Instruction Sets Output Type Instructions Right Side of the rungs
Depend on logic Preceding it
MOVE Instructions
Time & Counters
Internal Relays
Math Instructions
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5. Positive Going Coil = 1 shot
When we strobe an input such as a counter or timer we have problems with switch debounce.
To prohibit this condition we need only one pulse per switch activation
The 1 shot solves this problem by only allowing 1 shot regardless of the switch bouncing
You can have a PGC as an output but micro90 does not like having multiple outputs with a PGC in it.
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6. Types Of Counters Up Counter Down Counter Counts Up (Increments Up)
The output is on when when current value = or greater than preset value
Down Counter
Transition from off to on causing current value to decrease by 1
Output is on when current value is less than or equal to preset value
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7. Differences between PLCs
GE PLCS
Counters and Timers are functions that give an output
AB PLCS
Counter and timers are functions that give an output
MITSUBISHI PLCS
Like Koyo and TI the counter and timer are outputs, that is they are not a function they are an output
The address of output is used to drive or do something
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8. Counter Set up
To address a counter or any other type of internal function use %R
Every counter or timer address must be incremented by 3 words
%R1 %R4 %R7
The counter uses 3 Register #s to store the data
If we don’t, registry is over lapped
Trying to save the data for 2 counters in one location
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9. Addressing A Counter The Input
This is the location where the change of state is observed (can be from an actual input, other function ie counter or and output)
The Reset
An address that confirms resetting the PV (preset value) back to its original value. Note that we can “lock” the counter out if the reset input is forced ON
If we need to create a reset that resets the Counter we can in the Reset line (parallel with actual reset command such as %I2) use a FST_SCN a first scan command that will reset all values when the PLC is first scanned in the run mode
The PV
The Preset value is the address numerically after the counter number
If we have %R2 as a counter then %R3 is the PV registry
Highest Number is 32767
We can have a Hardcode value a set value such as 10, ect.
Or we can have %R, %AQ or a %AI variable as its PV
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10. Universal Counter Info
All PLCs use 3 words for addressing the counter
GE uses a %R register because it gives greatest flexibility
For example Mitsubishi has C=256, T=256 and D=1028 so what if you need 270 counters cannot do it!
GE has in the Micro %R so that gives us 685 (2056/3) anything Timer or Counters
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11. Special Note Resetting R value
We have to have an ALWAYS_ON in series with the INPUT rung to COUNTERS and TIMERS on the Series 90 Micros. It is caused by a function of the programming of the VersaPro software.
In the Mitsubishi PLC the command is 9038
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12. Where to Get More Information
See Web Site
VersaPro 2.02/3 users guide
Series 90 Micro Workshop
Believe it or not the help in VersaPro
Then Index
Look up counters
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