Three-point control with feedback
- Block name
- ST call
- Library
- Version
- Description
- Inputs
- Outputs
- Function
- Application example

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

Input	Typ	Description	Default value
DX	REAL	Insensivity to input signal (0…100 %)	1
FBK	REAL	Feedback signal (0…100 %)	0
IN	REAL	Input signal (0…100 %)	0
TOVER	TIME	Extra travel time behind fully open or fully closed position for safe opening or closing	1s
TRUN	TIME	Travel time between fully open and fully closed positions (0 to 100 % or back)	10s

Outputs

Output	Typ	Description
CLOSE	BOOL	Command to open
OPEN	BOOL	Command 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.

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