S5 AWL Command: SD (On-Delay Timer)
S5 AWL instruction SD (On-Delay): Output goes TRUE only after the input has been TRUE for the full timer duration. Resets if input goes FALSE before timer expires.
S5 AWL Command: SD (On-Delay Timer)
SD starts an on-delay timer. The timer output goes TRUE only after the input (VKE) has been continuously TRUE for the full timer duration. If the input goes FALSE before the timer expires, the timer resets to zero — the output never becomes TRUE.
Syntax
L KT xxx.y
SD T n
S7 Equivalent
| S5 AWL | S7 Function | IEC 61131-3 |
|---|---|---|
| SD | S_ODT | TON (On-Delay Timer) — 1:1 match |
SD → TON is a direct, exact equivalent. This is the easiest S5 timer to migrate.
Timing Diagram
E 0.0: ____/‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾\____
T 1: ______________/‾‾‾‾‾‾‾\____
|--5s--|
Code Example
U E 0.0
L KT 050.1 // 5 seconds
SD T 3
U T 3
= A 4.0 // ON after 5 seconds of continuous input
Typical Use
The most common timer type. Used for: motor startup delays, debouncing inputs, safety time delays (e.g., "door must be closed for 3 seconds before machine starts"), process time monitoring.
Related: SS (Retentive On-Delay) — Does NOT reset when input goes FALSE
Part of the S5 AWL Command Reference. Maintained by PLCcheck.ai.
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