FB_HVACPWM

This function block generates a pulse width modulated signal from the analog input signal rYIn. Furthermore, a minimum switch-on time can be parameterized.

VAR_INPUT

eDataSecurityType : E_HVACDataSecurityType;
bSetDefault       : BOOL;
bEnable           : BOOL;
rYIn              : REAL;
bReset            : BOOL;

eDataSecurityType: If eDataSecurityType:= eHVACDataSecurityType_Persistent, the persistent VAR_IN_OUT variables of the function block are stored in the flash of the computer if a value changes. For this to work, the function block FB_HVACPersistentDataHandling must be instanced once in the main program, which is called cyclically. Otherwise the instanced FB is not released internally.

A change of value can be initiated by the building management system, a local operating device or via a write access from TwinCAT. When the computer is restarted the saved data are automatically read back from the flash into the RAM.

Application example: example_persistent.zip

If eDataSecurityType:= eHVACDataSecurityType_Idle the persistently declared variables are not saved in a fail-safe manner.

Notice
A cyclically changing variable must never be linked with the IN_OUT variable of a function block, if eDataSecurityType:= eHVACDataSecurityType_Persistent. It would lead to early wear of the flash memory.

bSetDefault: If the variable is TRUE, the default values of the VAR_IN_OUT variables are adopted.

bEnable: The function block is enabled if bEnable = TRUE.

rYIn: Analog input variables of the function block (0%..100%).

bReset: Acknowledge input in the event of a fault.

VAR_OUTPUT

bOut               : BOOL;
rYOut              : REAL;
bInvalidParameter  : BOOL;

bOut: PWM signal.

rYOut: Output of the input variable of the function block (0%..100%).

bInvalidParameter: Indicates that there is an incorrect input parameter. bInvalidParameter must be acknowledged with bReset.

VAR_IN_OUT

tPWMPeriod      : TIME;
tMINPowerOnTime : TIME;

tPWMPeriod: Period of the PWM signal. The variable is saved persistently. Preset to 30 min.

tMINPowerOnTime: Minimum switch-on time of the pulsed output bOut. The variable is saved persistently. Preset to 0 s.

Figure: Scope2 recording for additional explanation of the mode of operation of the function block. The output (bOut = TRUE) is set on enabling the function block (bEnable = TRUE). See also sections 1 and 5.
A change in the input variable during a running period is only taken into account in the next period. See also sections 2, 3 and 4.

Requirements

Development environment	required library	required function
TwinCAT 3.1 build 4022.16 or higher	Tc2_HVAC V3.3.1.0	TF8000 \| TC3 HVAC V1.0.0.0