Step controller for electrical loads

Linear or binary output control

With parameter SYS-04 the user can select if the digital output stages will be controlled in a linear or binary way.


Depending on the total number of stages (SYS-01 + SYS-02), the "SeqSignal"  output of the module will provide a coded signal for the add-on module for step-controller.


The "SeqSignal" output represents the number of stages, which are still needed. If the signal has a positive value, the steps will be controlled in a linear way; when the input signal has a negative value the steps will be controlled in a binary way. If binary was selected, Stage1 is the lowest significant bit and Stage4 is the most significant bit.


Description

Default value

SYS-01: Total number of digital stages

4

SYS-04: Conversion mode

0 = linear

1 = binary

0


Step controller output signals

The SCB_ElectricHeater macro is a step controller with up to four digital output stages  ("Stage1Cmd"..."Stage4Cmd") and one analogue output "HeatControl", which varies from 0% to 100% between each digital step.
The total number of steps is defined by parameter SYS-01 + SYS-02 and is displayed in the display value DISP-01, while the value of setting SYS-03 defines the differential for switching-off the digital stages. SYS-03 is always a percentage of the heating signal allocated to one control stage. The signal allocated to one stage is equal to 100 divided by the total number of stages.
Next picture explains the output behaviour depending on the input signal coming from the strategy, with three digital output steps and an active analogue output where SYS-03 is set to a value of 50%, while the step-controller is defined to function in a linear way.



Description

Default value

SYS-01: Total number of digital stages

4

SYS-02: Enable analog output

0

SYS-03: Stage differential

50 %

SYS-04: Conversation mode

0 = linear

1 = binary

0


Control signal output

In case of an increasing control signal, the "HeatControl" provides an ascending control signal of 0…100% between each stage. At the moment, the "HeatControl" reaches the maximum value of 100%, a digital stage will be switched on and the "HeatControl" drops to 0% again. After the last stage (which was defined by parameter SYS-01), has been switched on, the "HeatControl" will stay at its maximum value. Regardless of the adjustment of the differential (SYS-03).


If an analogue output is configured, the modulating signal will descend from 100 to 0% if the control signal drops.

Whenever a digital stage is switched off, the analogue signal will start to decrease from (100% - SYS-03) between stages, as shown in next diagram.


Description

Default value

SYS-03: Stage differential

50 %


- If SYS-03 is set to x %, the descending "HeatControl" will vary from (100 - x) to 0%.This means, that:

- If SYS-03 is set to 0 %, the descending "HeatControl" will vary from 100 to 0%;

- If SYS-03 is set to 100 %, then there will be no variation on the descending "HeatControl" and this signal will stay at 0%.


Note: The Control Signal is not affected by the blocking on/ off times, defined by the parameters STx-01 and STx-02.