GE Counters and Order of Operation

1. GE Counters and Order of Operation MAIN 222 Industrial Controllers

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

3. Program Execution • In class activity Order of Operations • What is the difference between the programs? • Which one is the one shot?

4. Instruction Sets • Output Type Instructions • Right Side of the rungs • Depend on logic Preceding it • MOVE Instructions • Time & Counters • Internal Relays • Math Instructions

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.

6. Types Of Counters • Up 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

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

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

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, 10000 ect. • Or we can have %R, %AQ or a %AI variable as its PV

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 90 2056 %R so that gives us 685 (2056/3) anything Timer or Counters

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

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