WAGO 750-830 Manual page 200

200 • Fieldbus Communication
BACnet/IP
Caretaker with
main switch
Switch for
vacacion operation
Employee with
light switch
Fig. 4-1: Examples of a prioritization
Minimum On/Off
Some objects, such as the Binary Output Object, have the properties "Mini-
mum_Off_Time" and "Minimum_On_Time". If these properties are assigned
values (Unsigned32), these indicate within seconds how long the current state
must be maintained before another can occur. In this way, the frequency of
switching is controlled. A minimum on or off time is, for example, used to
control sun blinds for shading a building. We do not want the blinds to go up
or down every minute depending on the cloud cover; rather, we want them to
close during longer periods of sunshine and to be up in a secure position dur-
ing bad weather or long-lasting storms.
Example:
Control of the sun blinds in an office complex is effected through the Write-
Property services of three devices (switches). All three services deliver a pri-
ority parameter together with the command to the blinds to go up and down
(UP/DOWN). This parameter is entered in the priority list in the object that
controls the sun blinds. Now the value of the Present_Value of the object that
features the highest priority (lowest number) is accepted. In this example, a
300 second Minimum_On_Time and a 600 second Minimum_Off_Time is as-
sumed. This means that the minimum time that the sun blinds can stay in the
highest position is 5 minutes, and only after this time has elapsed can new
switching tasks be carried out. The minimum off time, in which the sun blinds
are closed, must be at least 10 minutes before switching back.
Property Present_Value
Value ON
1
Priority
Property Present_Value
Value OFF
7
Priority
Property Present_Value
Value ON
Priority 8
_________
Priority array
_________
_________ 1 ON
2
_________
_________ 3
4
_________
Light switching
_________ 5
6
_________
_________ 7 OFF
_________ 8 ON
_________ 9
_________ 10
11
_________
_________ 12
13
_________
_________ 14
15
_________
_________ 16
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
G083015e1-4