====== Time scheduler, real ======

{{:en:mervis-ide:35-help:t18.png}}

===== Block name =====

T18_REAL_SCHEDULER

===== ST call =====

<code st-iec>
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
</code>

===== 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.

The output value is recalculated at 30-second intervals.
===== 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 IDE 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 [[en:mervis-ide:35-help:035-software_basic:060-libraries:040-hvac:020-time-programs:015-t19_int_scheduler|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.\\


{{:en:mervis-ide:35-help:t18_example.png}}

In the editor, the basic setpoint is set to 18 °C, and the operation hours setpoint is 21 °C:

{{:en:mervis-ide:35-help:t18_example2.png}}