kitControl-DigitalInputDemux

This component provides four StatusBoolean outputs from one StatusNumeric input.

DigitalInputDemux 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 DigitalInputDemux component then de-multiplexes the analog voltage into four StatusBoolean outputs.

Figure 112. DigitalInputDemux object application

The illustration shows four volt-free contacts, such as door status, connected to a four-channel digital input multiplexer. The IO/DIM4 multiplexer device is manufactured by Titan Products Ltd., although similar suitable devices are available from other equipment suppliers. The IO/DIM4 multiplexer is microprocessor-based and designed to convert four separate digital input signals into a single analog 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. Its output feeds the DigitalInputDemux object. Finally, the DigitalInputDemux object provides four status Boolean outputs, which represent the status of the original four contacts.

Property	Value	Description
In	number (defaults to 0.00) and null definition	Provides a StatusNumeric value for this object to serve as 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. When null is checked, the value displayed defaults to the incoming value from the device. If you remove the check mark you can configure the`In` value.
In Offset	positive or negative number to two decimal places	Defines an offset for the input.
Out1	read-only `true` or `false` (default)	Provides a status Boolean value, which the component sets to `true` if the `In` property contains a value equivalent to the value set as the `Out1 Value` property.
Out2	read-only `true` or `false` (default)	Provides a status Boolean value, which the component sets to `true` if the `In` property contains a value equivalent to the value set as the `Out2 Value` property.
Out3	read-only `true` or `false` (default)	Provides a status Boolean value, which the component sets to `true` if the `In` property contains a value equivalent to the value set as the `Out3 Value` property.
Out4	read-only `true` or `false` (default)	Provides a status Boolean value, which the component sets to `true` if the `In` property contains a value equivalent to the value set as the `Out4 Value` property.
Out1 Value	number to two decimal places (defaults to 4.80)	Sets a value, which corresponds with the equivalent setting in the multiplexer device to represent the status of the digital input 1.
Out2 Value	number to two decimal places (defaults to 2.40)	Sets a value, which corresponds with the equivalent setting in the multiplexer device to represent the status of the digital input 2.
Out3 Value	number to two decimal places (defaults to 1.20)	Sets a value, which corresponds with the equivalent setting in the multiplexer device to represent the status of the digital input 3.
Out4 Value	number to two decimal places (defaults to 0.60)	Sets a value, which corresponds with the equivalent setting in the multiplexer device to represent the status of the digital input 4.
Dead Band	number to two decimal places (defaults to 0.10)	Sets a tolerance value to prevent output ‘chatter’ due to a fluctuating input value. This property operates purely on the input `In` value.

Dead band example

An on-site multiplexer device with four digital inputs (DI) feeds the DigitalInputDemux component. DI1 and DI2 are open (off) and DI3 and DI4 are closed (on). The combined voltage weighting of DI3 and DI4 is 1.8v. An NDIO universal input transmits the combined voltage weighting of DI3 and DI4 (1.8v) to the DigitalInputDemux component. The DigitalInputDemux object then faithfully de-multiplexes this signal, setting Out3 and Out4 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 from adversely upsetting your control strategy.

Figure 113. Operation of the Dead Band property

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.