Table of Contents

Time scheduler real, basic

Block name

T18_REAL_SCHEDULER_BASE

ST call

PROGRAM TEST_T18_BASE
  VAR 
        FB : LIB.HVAC.V1_0.T18_REAL_SCHEDULER_BASE := (TPGVALUE := [(STARTTIME := 0, STATE := 0),
       (STARTTIME := 370, STATE := 1),
     (STARTTIME := 650, STATE := 3),
     (STARTTIME := 2070, STATE := 8)], 
      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). This scheduler doesn't  support exceptions. Exceptions are implemented in T18_REAL_SCHEDULER.

The output value is recalculated at 30-second intervals.

Inputs

Input TypeDescription
CURRENTTIME DT Date and time in case that other date and time than system date and time shall be used
DEFAULTVALUEREALOutput value if en=false

Outputs

OUTREALCurrent time schedule state

Description of internal structures

DescriptionImportance
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 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: