Color Temperature

A Color Temperature object controls the colour of white light, in Kelvin. A lighting device uses it so a client can make light warmer or cooler. It can be set directly or faded with a colour command.

Typical uses

• Warm white in the evening, cool white at midday
• Tunable white panels
• Match light to a daily rhythm
• Fade between two white tones

Key properties

Property	What it holds
Present_Value	The target colour temperature in Kelvin. The standard allows 1000 to 30000.
Color_Command	Starts a fade or ramp to a new colour temperature.
Tracking_Value	The colour temperature the output has reached right now while it fades.
In_Progress	Shows whether a fade is under way.
Default_Color_Temperature	The value used when the object has no other instruction.

How it behaves

The standard defines no intrinsic event algorithm for this type. A lighting output points to a Color Temperature object to say which one controls its white tone.

With the CAS BACnet Stack

Enable it with the STACK_OPTION_OBJECT_TYPE_COLOR_TEMPERATURE build option and add each object with BACnetStack_AddObject. Present_Value is Unsigned, so serve it through the callback you register with BACnetStack_RegisterCallbackGetPropertyUnsignedInteger, and serve the other properties through the callback that matches each datatype. Color_Command cannot be served: there is no callback for a colour command, so a client cannot fade or ramp the object through it in this release.

Related object types

Color, Lighting Output, Binary Lighting Output, Channel

Properties

The properties ASHRAE 135-2024 clause 12.66 defines for this object type.

How to read the table:

• Conformance is what the standard asks of every object of this type: R is required, W is required and writable by a client, O is optional. A digit after the letter marks a condition in the standard that decides when the property is present or writable, such as support for intrinsic reporting.
• Present by default: yes means the stack presents the property as soon as you add the object; no means it is optional and you turn it on with BACnetStack_SetPropertyEnabled. This is the stack’s starting setup, so it can differ from the conformance code.
• Writable is whether a client can write the property by default. Change it with BACnetStack_SetPropertyWritable.
• not in profile means the stack does not offer this property for this object type.
• Value when your callback does not answer: “Held by the stack” means the stack stores and serves the value itself and does not ask your callbacks. Otherwise it is the value the stack answers when your callback declines or is not registered.

Property	Datatype	Conformance	Present by default	Writable	Value when your callback does not answer
Object_Identifier	BACnetObjectIdentifier	R	yes	no	Held by the stack.
Object_Name	CharacterString	R	yes	no	"Object <type>,<instance>", such as "Object 0,1" for Analog Input 1.
Object_Type	BACnetObjectType	R	yes	no	Held by the stack.
Present_Value	Unsigned	W	yes	yes	No default: value-not-initialized.
Tracking_Value	Unsigned	R	yes	no	0
Color_Command	BACnetColorCommand	W	yes	yes	No default: the read fails.
In_Progress	BACnetColorOperationInProgress	R	yes	no	0
Default_Color_Temperature	Unsigned	R	yes	no	0
Description	CharacterString	O	no	no	""
Default_Fade_Time	Unsigned	R	yes	no	0
Default_Ramp_Rate	Unsigned	R	yes	no	0
Default_Step_Increment	Unsigned	R	yes	no	0
Min_Pres_Value	Unsigned	O1	no	no	0
Max_Pres_Value	Unsigned	O1	no	no	0
Transition	BACnetColorTransition	O	no	no	0
Value_Source	BACnetValueSource	O2,3,4	no	no	No default: the read fails.
Audit_Level	BACnetAuditLevel	O5	no	no	0
Auditable_Operations	BACnetAuditOperationFlags	O5	no	no	An empty bit string.
Tags	BACnetARRAY[N] of BACnetNameValue	O	no	no	No default: the read fails.
Property_List	BACnetARRAY[N] of BACnetPropertyIdentifier	R	yes	no	Held by the stack.
Profile_Location	CharacterString	O	no	no	""
Profile_Name	CharacterString	O	no	no	""