Table of Contents

Three-point control with feedback

Block name

T6_THREE_POINT_CONTROL_FEEDBACK

ST call

PROGRAM TEST_T6 
   VAR 
        REAL1,REAL2,REAL3: REAL;
        TIME1,TIME2 :TIME;
      BOOL1,BOOL2 :BOOL;
      FB: LIB.HVAC.V1_0.T6_THREE_POINT_CONTROL_FEEDBACK;
  END_VAR
 FB(IN := REAL1, FBK:= REAL2, TRUN:= TIME1, TOVER:= TIME2, DX:= REAL3, CLOSE=> BOOL1, OPEN=>BOOL2);
END_PROGRAM

Library

LIB\HVAC

Version

V1.0

Description

The block converts a 0…100 % signal to opening and closing pulses to control a three-point peripherial, such as a valve or damper actuator. To determine the real actuator position, a feedback signal is used.

Inputs

InputTyp Description Default value
DX REALInsensivity to input signal (0…100 %) 1
FBK REALFeedback signal (0…100 %) 0
IN REALInput signal (0…100 %) 0
TOVERTIMEExtra travel time behind fully open or fully closed position for safe opening or closing1s
TRUN TIMETravel time between fully open and fully closed positions (0 to 100 % or back) 10s

Outputs

OutputTyp Description
CLOSE BOOLCommand to open
OPEN BOOLCommand to close

Function

This block is useful for valves which provide analogue position feedback signal 0..10 V or resistance - the signal is brought to the FBK input, and the block controls over the OPEN and CLOSE signals so as the FBK signal is equal to IN. It is, actually, a controller trying to keep the FBK signal the same as IN.

Application example