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Siemens TX-I/O™ Module system – Functions and operation CM110561en_08
Building Technologies Digital output functions 2018-10-25
5.9 Three-position control signal
(BO 3-Pos Relay, BO-3-Pos Triac / Y250T))
For open/close control of three-position actuators without feedback (position
potentiometer), e.g. for
– Valve actuators
– Damper actuators
– Third-party actuators
The function uses two I/O points which must be on the same module and adjacent to
each other. I/O point (n) = Open, I/O point (n + 1) = Close.
• The function converts the process value into 3-position positioning signals.
An internal stroke algorithm calculates the required length of the OPEN or CLOSE
pulses from the actuator runtime and the position specified in the process value.
No position feedback is required from the actuator.
• The function supports asymmetrical actuators with different opening and closing
runtimes. However, this function can only be used if it is also supported by the bus
master.
Break time
Pause between opening
0...25.5 s (0.1 s)
Reaction Time
Additional runtime when
0...50.0 s (0.0 s)
Backup mode Response of process value
in the event of bus failure
Keep = Last active value
No = 0% (No)
Backup Value
Backup value if
Backup Mode = Value
0.01...100% (0 %)
Synchronization Synchronization mode
Direction
Inversion of the outputs to
fix incorrect wiring
False (normal) (False)
Asymmetric runtimes can be set as parameters (if supported by the bus master).
Delay time before the actuator changes direction
Additional runtime when traveling to or from 0 % (clearance between motor and drive).
Note: Reaction Time is not part of the stroke model.
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