FB_HVACMux8

Application

This function block evaluates the FIFO memory from FB_HVACRedundancyCtrlEx. The inputs are mapped to the respective outputs according to a FIFO table.

If this function block is used, for example, to control speed-controlled fans, then the setpoints from a controller cascade can be assigned to the respective outputs (drives). To do this, the setpoints are applied to the inputs of FB_HVACMux8. The processing takes place with the aid of information from the FIFO memory (which drive is running and in which order did switch-on take place).

Example:

There are 4 drives with speed controllers (SetFC1 – SetFC4), of which a maximum of three should be running. The control range of 0 to 300% is divided into 3 setpoints (Set1 to Set3). The output arrFiFo of FB_HVACRedundancyCtrlEx supplies FB_HVACMux8 with the assignment description. In the sample the array contains: 2,3,0,0,0,0,0,0. Therefore Q2 was switched on first and then Q3. As a result rIn1 is now output on rQ2 and rIn2 on rQ3 in FB_HVACMux8.

VAR_INPUT

arrFiFo            : Array[1..8] of INT;       0 - 8
rIn1 - rIn8        : REAL;                                 

arrFiFo:contains the assignment table. The first value indicates where the first input will be copied to, the second value indicates where the second value will be copied to, etc. Identical values are permitted. No assignment is made for "0.

rIn1 - 8: setpoints to be mapped.

VAR_OUTPUT

rQ1 - rQ8     : REAL;                
bErr          : BOOL;

rQ1 -rQ8: actuator setpoint, input value mapped according to the FIFO table.

bErr: value range in the FIFO table was exceeded; 0 to 8 is permissible.