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.
Application example
