FB_DALI102ConstantLightControl

The FB_DALI102ConstantLightControl function block provides the basic functions for implementing constant light regulation.

The system attempts to regulate to a specified setpoint (nSetpointValue) by dimming up and down cyclically. The control dynamics are determined by a dead time (tDeadTime). The dead time defines the settling time between the individual DALI commands for changing the output value (nActualLevel). The smaller the dead time, the faster the control. A freely definable hysteresis (nHysteresis) prevents continuous oscillation around the setpoint. If the actual value is within the hysteresis range around the setpoint, the output value of the DALI control gears is not changed.

Operation

The function block offers the option to address a single DALI control gear via a short address, several DALI control gears via a group address, or all DALI control gears of a DALI line via a broadcast.

The variables minLevel, maxLevel, fadeRate, fadeTime, extendedFadeTimeBase and extendedFadeTimeMultiplier are parameters that are stored separately in each DALI control gear. These variables can be changed in the DALI control gears by writing to the respective properties and with a positive edge at the input bInitialize.

Control

The output value of the DALI control gears can be switched by positive edges at the inputs bOn, bOff and bToggle. If the DALI control gears are switched on and control is active (bEnable = TRUE), then they are regulated to the specified setpoint. If the control is not active (bEnable = FALSE), the output value of the DALI control gears remains unchanged.

The step-by-step adaption of the output value of the DALI control gears is carried out with the DALI commands STEP UP/STEP DOWN or UP/DOWN.

If the control deviation (nDeviation) is greater than nHysteresis, the DALI command UP/DOWN is used to adjust the output value. The number of steps by which the output value changes is specified by the eFadeRate property.

If the control deviation is between nHysteresis/2 and nHysteresis, the DALI command STEP UP/STEP DOWN is used and thus the output value is only adjusted by one step.

If the control deviation is smaller than nHysteresis/2, the output value of the DALI control gears remains unchanged.

The control deviation is calculated from nSetpointValue - nActualBrightness.

The dead time (tDeadtime) specifies the time after which the output value is adapted. The DALI command STEP UP/STEP DOWN or UP/DOWN is called only once per control cycle.

Operation via the inputs bOn, bOff, and bToggle

The output value of the DALI control gears can be changed immediately by positive edges at the inputs bOn, bOff, and bToggle. This is independent of whether the control has been enabled or disabled (bEnable).

The variables fadeTime, extendedFadeTimeBase, and extendedFadeTimeMultiplier specify the speed at which the output value is changed when the DALI control gears are switched on via bOn or bToggle. Switching off the DALI control gears by bOff or bToggle takes place immediately. In this case, nSwitchOnLevel is used as the switch-on value. This value must lie in the range of the properties nMinLevel and nMaxLevel.

DALI short address reference device (nReferenceDeviceAddress)

If several DALI control gears are addressed, the current output value of the reference DALI control gear is read out via nReferenceDeviceAddress. The DALI control gears are set to the desired output value, depending on the state of the reference DALI control gear.

The parameter nReferenceDeviceAddress is also used if the output value of the reference DALI control gear is read out cyclically in the background (tCycleActualLevel > 0 sec).

No reference DALI control gear is required if a single DALI control gear is to be controlled with the function block (eAddressType = E_DALIAddressType.Short). The output value of the individual DALI control gear is determined via nAddress. The parameter nReferenceDeviceAddress has no meaning in this case.

If nReferenceDeviceAddress is used, it must always contain the short address of a DALI control gear, which is also contained in the addressed DALI group. For a broadcast a DALI control gear with the corresponding short address must be present on the DALI line.

Sample

The following sample shows how a DALI light sensor can be combined with the FB_DALIConstantLightControl function block. In this sample, the PD11-BMS-FLAT DALI sensor from B.E.G. is used.

Since only the measured brightness is required, the instance for the movement sensor is disabled (property bEnableOccupancy).

The brightness is read out from the DALI sensor via the input bQueryBrightness. Thus, the instance for the light sensor can also be disabled (property bEnableBrightness).

At the end of the dead time, the output bControlCyclerEnding of the constant light regulation is set to TRUE. This positive edge is connected to the input bQueryBrightness of the DALI sensor. This means that the current brightness value is read out immediately before calculating the control deviation (nDeviation).

By deactivating both instances, the DALI sensor does not send any events and the DALI bus is not unnecessarily loaded.

The properties are initialized directly when the instance is declared. This means that explicit assignment at runtime is no longer necessary.

PROGRAM P_ConstantLightControl
VAR
  fbBrightness           : FB_DALI_BEG_PD11_BMS_V8_Flat(Communication.fbKL6821Communication) :=
                                 (bEnableOccupancy  := FALSE,
                                  bEnableBrightness := FALSE);
  fbConstantLightControl : FB_DALI102ConstantLightControl(Communication.fbKL6821Communication) :=
                                 (nMinLevel := 85,
                                  nMaxLevel := 254);
  bInitialize            : BOOL;
  bToggle                : BOOL;
  nBrightnessLevel       : UINT;
  nActualLevel           : BYTE;
  nDeviation             : DINT;
END_VAR

 Inputs

VAR_INPUT
  bInitialize              : BOOL := FALSE;
  bEnable                  : BOOL := TRUE;
  nAddress                 : BYTE;
  eAddressType             : E_DALIAddressType := E_DALIAddressType.Short;
  nSetpointValue           : UINT := 500;
  nActualBrightness        : UINT := 500;
  nHysteresis              : UINT := 30;
  tDeadtime                : TIME := T#5S;
  bOn                      : BOOL;
  bOff                     : BOOL;
  bToggle                  : BOOL;
  nSwitchOnLevel           : BYTE := 254;
  nReferenceDeviceAddress  : BYTE;
  tCycleActualLevel        : TIME := T#30S;
  nOptions                 : DWORD := 0;
END_VAR

Outputs

VAR_OUTPUT
  bError               : BOOL;
  ipResultMessage      : I_TcMessage;
  bBusy                : BOOL;
  bInitializing        : BOOL;
  nActualLevel         : BYTE;
  nDeviation           : DINT;
  bControlCycleEnding  : BOOL;
END_VAR

 Properties

All parameters that are written to the DALI control device via bInitialize are available as properties.

Requirements