About control points

A company’s data control model is based on experiential data collected from analog and other devices. Companies exploit this model to control building systems. Control points are the foundation for all points in the station, including all proxy points.

Figure 1. Simple control points


The framework supports eight simple control point components. Each reflects a combination of a data (value) category and a point type. The Points folder of the control palette provides a container for these types or categories of points.

VersionsBooleanNumericEnumString
Read-onlyBooleanPointNumericPointEnumPointStringPoint
WritableBooleanWritableNumericWritableEnumWritableStringWritable

Categories

The four categories apply to simple point components as well as to other components (for example, weekly schedules). These categories are:

  • Boolean represents a binary value with only two states, such as off and on.

  • Numeric represents an analog value, such as a temperature, level, rate or similar floating point number, or a varying count (integer). The system uses double-precision (64 bit) values.

  • Enum represents an enumerated state (more than two), such as a multi-speed fan with the states of: off, slow, and fast. Enums are often called multi-states or discretes. States typically derive from established integer value/state name pairs.

  • String represents one or more ASCII characters (alpha-numeric), often with some literal meaning.

Versions

Each of the four point categories provides two point versions:

  • A read-only version, which represents a data item that provides information and cannot be changed. Unlike the writable point version, there are no input type properties for read-only points. These four types are: BooleanPoint, NumericPoint, EnumPoint, and StringPoint.

    Note: As copied directly from the control palette, there is no application for read-only points. However, proxy points based upon read-only points, which are identical except for a non-null proxy extension and manner of creation, are both common and useful. For more details, see the Niagara Drivers Guide.

  • A writable version, which represents a data item that can be changed, as well as read (usually by the station). These types are: BooleanWritable, NumericWritable, EnumWritable, and StringWritable.

    An array of 16 InN inputs, each with a different priority level, is available to write a writable point’s value. By default, the point’s value can also be set with an operator-issued action (right-click command), available at priority levels 8 (override) and 1 (emergency).

Other point components

Other point components are found in the kitControl palette. Briefly, these components include:

  • Extensions, which expand a given point’s functionality. As needed, you can add one or more extensions to a point, each as a child of that point. Extensions add functionality in a modular fashion.

  • Time triggers provide periodic actions. These objects do not represent data, but, instead, they regularly fire a topic.

  • Other control objects are found in various folders of the kitControl palette. They provide station control logic based on data obtained from points. Example objects include numeric math objects, Boolean logic objects, and a PID loop, among others. Refer to the Niagara KitControl Guide.