On/Off-Delay Timer
The On/Off Delay (TON/TOF) adopts the state of a boolean tag (true or false) with a time delay.
It combines the two blocks known from the PLC world, on-delay timer (TON) and off-delay timer (TOF), in a single block.
Function parameters
| Source | Boolean tag whose state is adopted with a delay. |
| Switch on after | Time the source must be continuously on before the output switches on. With 0, the output switches on immediately. |
| Switch off after | Time the source must be continuously off before the output switches off. With 0, the output switches off immediately. |
How it works
When the source switches on, the Switch on after time starts. Once it has elapsed and the source is still on, the output switches on. If the source switches off before that, the process is cancelled and the output remains off. The same applies to switching off with the Switch off after time.
Depending on the settings, the following behavior results:
- Switch on after only (TON): Short signals are ignored. Example: A motor is only switched on when a condition has been present for more than 5 minutes.
- Switch off after only (TOF): The output remains active for a while after the source switches off. Example: A fan keeps running for another 10 minutes after being switched off.
- Both: Combination of both delays. Example: A pump only starts 30 seconds after the request and then keeps running for another 2 minutes.