The RaiseLower object provides a staged analog output designed to be used with a third party 2-relay hardware device but
also provides for operation of two digital outputs from normal IO hardware such as NDIO as an alternative control method.
The actuator should be able to sustain an overdrive at each boundary (for example, a clutch mechanism) as the Raise lower
object does not have proportional feedback or limit switch features. The RaiseLower component is available in the HVAC folder of the kitControl palette.
A typical application for the RaiseLower component is to control a reversible actuator in order to drive a coupled valve or damper either open or closed. The external hardware device consists of two on-board relays with volt free contacts that switch to provide power to either the “open” command of the actuator or the “close” command of the actuator. Either relay is activated for a proportion of the full scale drive time of the actuator (drive time is pre-defined by the manufacturer). The acceptable input to this device is 0 to10 volts, with staged control at 0v, 4v, 7v and 10v as detailed in Table 8.
Table 8. RaiseLower staged control voltage
| Volts | Raise | Lower | Function |
|---|---|---|---|
| 0 | Off | Off | Off |
| 4 | Off | On | Lower |
| 7 | Off | Off | Static |
| 10 | On | Off | Raise |
The Raise Lower object has the following properties:
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Propagate Flags
By default, this object maintains independent status flags from input-linked points. It is therefore possible to specify the “out” status to propagate from the input status. The Propagate Flags property specifies which status flags will propagate from the “In” property to the “Out” status flags. The object Propagate Flags property allows for selection of 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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Out
This is a status numeric value and is the analog output value from the object. This output has valid voltage outputs of 0v, 4v, 7v and 10v as illustrated in Table 8, depending on the function determined by the object.
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In
This property is a status numeric value typically connected to a modulated output of a Control object such as PID Loop. It has an input range of 0 to 100.
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Virtual Position
This is a slot that holds the value representing the virtual position of the actuator, as calculated by the RaiseLower object.
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Raise
This is a status boolean value which is set to
trueif the object determines that the output should command a “Raise” output. A Raise output is maintained for a period of time determined by the positive differential of “Virtual position” subtracted from the “In” slot, and is a relative proportion of the full scale drive time. In addition, if the “virtual position” of the object is calculated to be 100% (fully raised), then twice the drive time is asserted in order to synchronize the physical actuator with the calculated virtual position to compensate for realtime drift. -
Lower
This is a status boolean value which is set to
trueif the object determines that the output should command a “Lower” output. A Lower output is maintained for a period of time determined by the negative differential of “Virtual position” subtracted from the “In” slot and is a relative proportion of the full scale drive time. In addition, if the “virtual position” of the object is calculated to be 0% (Fully Lowered) then twice the drive time is asserted in order to synchronize the physical actuator with the calculated virtual position to compensate for realtime drift. -
Function
This property value displays operational information corresponding to the current activity of the object. Valid status values include: Off, Lower, Static, Raise.
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Dead Band
This should be set to a value that corresponds to a percentage of full scale drive time. The “In” value would have to exceed the dead band value before the “out” commands to “Raise” or “Lower”. The default value is 0.25, Range is 0 to 5.
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Drive Time
This should be set to a value that corresponds to the full scale drive time provided by the manufacturer.
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Midnight Reset Enabled
This should be set to
falseto inhibit a reset. A midnight reset invokes a synchronization cycle at midnight in order to compensate for realtime drift that may accumulate during normal operation of the actuator. The reset cycle will override an input signal for a period of twice the full scale drive time. -
Reset action
This action can be used to re synchronize the actuator through 0% (Fully Lowered) temporarily overriding an input signal for a period of twice the full scale drive time
Refer to Figure 42 for this example. An actuator having a 100 second full scale drive time and initialized values of the actuator and virtual position are 0% (synchronized at fully lowered). Should the input signal increase to 40% the “Raise” output turns on for 40% of the full scale drive time (40 sec). If a subsequent input is decreased to 15% the “Lower” output is active for 25% of full scale drive time (25 sec) moving the actuator to 15% open.
