Short description
The edge of an input pulse triggers a configurable time. The output is reset when this time has expired. An off warning can be output prior to the expiration of this time.
Connection |
Description |
Input Trg |
You trigger the time (off-delay) for the stairway switch with a signal at input Trg (Trigger). |
Parameter |
T: The output is reset (1 to 0 transition) when the off-delay time T has expired. T! determines the triggering time for the prewarning. T!L determines the length of the prewarning time. Retentivity set (on) = the status is retentive in memory. |
Output Q |
Q is reset after the time T has expired. A warning signal can be output before this time has expired. |
Parameters T, T! and T!L
The off-delay time T, the prewarning time T! and the prewarning period T!L can be provided by the actual value of another already-programmed function:
Analog comparator: Ax – Ay
Analog trigger: Ax
Analog amplifier: Ax
Analog multiplexer: AQ
Analog ramp: AQ
Analog math: AQ
PI controller: AQ
Up/Down counter: Cnt
You select the required function by the block number.
Timing diagram
|
0BA1, 0BA3: The prewarning time is set to 15 s. The T! and T!L parameters thus become obsolete. |
Changing the time base
You can change the prewarning time base and the period.
Time base T |
Prewarning time |
Prewarning period |
Seconds* |
750 ms |
50 ms |
Minutes |
15 s |
1 s |
Hours |
15 min |
1 min |
* makes sense only for programs with a cycle time of < 25 ms |
Description of the function
Output Q is set to 1 with a 0 to 1 signal transition at input Trg. The 1 to 0 transition at input Trg triggers the current time and output Q remains set.
Output Q is reset to 0 when Ta reaches the time T. Before the off delay time (T - T!) has expired, you can output a prewarning that resets Q for the duration of the off prewarning time T!L.
Ta is retriggered (optional) at the next high/low transition at input Trg and if Ta is expiring.
Scan cycle time
For information on how to determine the scan cycle time of a LOGO!, refer to the appendix of the LOGO! manual.