====== Three-point control with feedback  ======

{{:en:mervis-ide:35-help:t6.png}}

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

T6_THREE_POINT_CONTROL_FEEDBACK

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

<code st-iec>
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
</code>

===== 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 =====

{{:en:mervis-ide:35-help:t6_example.png}}