1. GE Timers and Isolation of the PLC System
MAIN 222
Industrial Controllers
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2. Caution with Counters and Timers
When using a timer or counter we have a possible problem with switch bounce or multiple counts
YOU MAY NEED A ONE SHOT
this will only allow for a single increment not multiple
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3. Timers
ON-Delay if you want to program a time delay before an instruction becomes true
Normal Timer
Off-Delay off-delay timer increments while no accumulator is present, and resets to 0 when there is an accumulator. Time may be counted in tenths of seconds or hundredths of seconds, or thousandths of seconds, depending on the time-base. The range for this timer is 0 to +32,767 time units.
When there is an accumulator available to the off-delay timer, it sets CV to 0. If the accumulator is removed from the function, the timer starts incrementing CV.
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4. Timer OFF example
In this example, an Off Delay Timer is used to turn off an output (%Q00001) whenever an input (%I00001) turns on. The output is turned on again 5.0 seconds after the input goes off.
Note: CV (the current value) does not display on the version of this function.
Variable Declaration
Name Type Length Reference
%I00001 BOOL 1 %I00001
%Q00001 BOOL 1 %Q00001
%R00004 OFDT_TENTHS 1 %R00004
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5. ON Timer Example
In this example, an On Delay Stopwatch timer is used to create a signal (%Q00011) that turns on 8.0 seconds after %Q00010 turns on, and turns off when %Q00010 turns off.
Note: CV (the current value) does not display on the version of this function.
Variable Declaration
Name Type Length Reference
%Q00010 BOOL 1 %Q00010
%Q00011 BOOL 1 %Q00011
%R00001 ONDTR_TENTHS 1 %R00001
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6. Addressing A Timer The Input The Reset The PV
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
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
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7. Special Note
We have to have an ALWAYS_ON in series with the INPUT rung to COUNTERS and TIMERS on the Series 90 Micros.
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8. 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
Timer Function (Versa Mas Series 90-30)
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9. Input / Output Isolation
Why Isolate ? Isolate What?
The PLC is a messenger of allowing on or off a signal
Its job is not to provide current, voltage
Need to separate the high voltage side from internal side of PLC
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10. Input Isolation
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11. Output Module
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