The Digital Input Demux (Demultiplexer) object provides four status boolean outputs from one StatusNumeric input. This component
is available in the Util folder of the kitControl palette.
A typical application for this demultiplexer object is in association with a multiplexer module to expand the IO capacity of a system. The multiplexer creates a single analog voltage output to represent the state of up to four digital inputs. The analog voltage is then demultiplexed into four status boolean outputs by the DigitalInputDemux object.
The DigitalInputDemux component has the following properties:
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Propagate Flags
By default, this object maintains independent status flags from input-linked points. However, as a configuration option you can specify “out” status to propagate from the input status. The propagate flags property specifies which status flags propagate from the “In” property to the “Out” status flags. The PropagateFlags property allows you to select any combination of the following status types for propagation:
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disabled
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fault
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down
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alarm
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overridden
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In
This is a StatusNumeric value for this object and is the input analog value from the multiplexer which represents the state of the four digital inputs. This input must be valid for the object to function.
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Out1
This is a status boolean value which is set to
trueif the object determines that the “In” property contains a value equivalent to the value set as the Out1 Value property. -
Out2
This is a status boolean value which is set to
trueif the object determines that the “In” property contains a value equivalent to the value set as the Out2 Value property. -
Out3
This is a status boolean value which is set to
trueif the object determines that the “In” property contains a value equivalent to the value set as the Out3 Value property. -
Out4
This is a status boolean value which is set to
trueif the object determines that the “In” property contains a value equivalent to the value set as the Out4 Value property. -
Out1 Value
This should be set to a value which corresponds with the equivalent setting in the multiplexer device to represent the status of digital input 1. The default is 4.80.
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Out2 Value
This should be set to a value which corresponds with the equivalent setting in the multiplexer device to represent the status of digital input 2. The default is 2.40.
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Out3 Value
This should be set to a value which corresponds with the equivalent setting in the multiplexer device to represent the status of digital input 3. The default is 1.20.
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Out4 Value
This should be set to a value which corresponds with the equivalent setting in the multiplexer device to represent the status of digital input 4. The default is 0.60.
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Dead Band
The Dead Band allows you to set a tolerance value to prevent ‘chatter’ of the outputs due to fluctuations of the input value. The Dead Band function operates purely on the input “In” value.
In the example shown in Figure 19, the DigitalInputDemux object is fed from a multiplexer device on site which is connected to four digital inputs (DI). DI1 and DI2 are in an open (off) condition and DI3 and DI4 are closed (on). The combined voltage weighting of DI3 and DI4 is 1.8v which is transmitted to the DigitalInputDemux object via an NDIO universal input. The DigitalInputDemux object then faithfully demultiplexes this signal so that “Out3” and “Out4” are both set to ‘True’.
In practice, a voltage drop occurs on the received signal and the Dead Band property allows you to engineer in some protection for this fluctuation to prevent it adversely upsetting your control strategy. The Dead Band property in this example is set to 0.10 which is applied to the “In” value. The Dead Band function operates equally in both positive and negative sense on the “In” value. In this example therefore, all values from 1.75 through to 1.85 are valid.
The default value of the Dead Band property is 0.10.
The DigitalInputDemux object has no actions.
In the example shown in Figure 20, four volt-free contacts, such as door status, are connected to a 4 channel digital input multiplexer. The IO/DIM4 multiplexer device shown is manufactured by Titan Products Ltd., although similar suitable devices are available from other equipment suppliers. The IO/DIM4 multiplexer is microprocessor based and is designed to convert 4 separate digital input signals into a single analogue voltage output. Each combination of digital input signal is converted to an output voltage level which is then connected to one universal input of an NDIO IO-16 module. The NDIO universal input is configured as a “Voltage Input Point” and its output feeds the DigitalInputDemux object. Finally, the DigitalInputDemux object provides 4 status boolean outputs which represent the status of the original 4 contacts.
