Lessons · Industrial control · on-delay timer (TON)
On-delay
[TON T1 2s] accumulates while its input is true and sets T1.DN when it reaches the preset; it resets when the input drops.
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What it is for
Debounce, warm-up, staggered starts, 'hold for 3 seconds to confirm'.
How to think about it
What starts the timer, and what reads DN? The timer sits on a rung whose conditions start it; a separate rung reads T1.DN to act. For an off-delay, time the inverse.
Worked example
[Heater] [TON Warm 5s]Times while heater is on.
[Warm.DN] (Ready)Ready 5 seconds after the heater came on.
Your turn
Read the done bit.
[T1.] (Out)
Run a rung and watch the scan
The trap
Reading the timer's own rung to know it finished. The DN bit is the output; the rung is the input.
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