Documentation
Real Scheduler (T18)
Time scheduler, real
Block name
T18_REAL_SCHEDULER
ST call
PROGRAM TEST_T18
VAR
FB : LIB.HVAC.V1_0.T18_REAL_SCHEDULER := (TPGVALUE := [(STARTTIME := 0, STATE := 0),
(STARTTIME := 370, STATE := 1),
(STARTTIME := 650, STATE := 3),
(STARTTIME := 2070, STATE := 8)],
EXCEPTIONS := [(STARTTIME := 1000, ENDTIME := 2000, STATE := 3)]);
DT1:DT;
REAL1:REAL;
END_VAR
DT1:=getlocaltime();
FB(CURRENTTIME:=DT1, OUT=> REAL1);
END_PROGRAM
Library
LIB\HVAC
Version
V1.0
Description
Time scheduler is a source of a real variable which value changes according to a weekly schedule with maximum 42 events (changes of state). Exception events (exceptions) defined by date, time, and state can be inserted.
Inputs
| Input | Type | Description |
|---|---|---|
| CURRENTTIME | DT | Date and time in case that other date and time than system date and time shall be used |
| DEFAULTVALUE | REAL | Output value if en=false |
Outputs
| OUT | REAL | Current time schedule state |
Description of internal structures
| Description | Importance |
|---|---|
| STATE | Current state of the time program |
| STARTTIME | Minutes from the beginning of the day |
Function
The time scheduler compares current date and time with the definition table and sends the actual state to the output. The output is a real value. The time scheduler can be edited from Idekit Studio or HMI - LCD display, web interface, touchscreen, SCADA or another client).
Application example
Time scheduler is used to specify variable setpoints in time directly. (Use T19_INT_SCHEDULER for multistate output, like switching between Comfort, Standby, and Off, and boolean scheduler to enable plant operation according to a time schedule.)
At the image below, T18 is used to generate a temperature setpoint for an air handling unit. A correction from a room unit (AHU1_TEMP_CORR) is added, and the result is brought to the air supply PI controller.
In the editor, the basic setpoint is set to 18 °C, and the operation hours setpoint is 21 °C:
