The scenario
A controls engineering student designing a batch process sequence needs a PLC ladder logic diagram for a mixing tank.
What is in this drawing
Read the decisions behind it.
01
Rung 1+2 parallel seal-in latches the fill valve even after the start button is released.
02
High-level sensor (XIC rung 3) prevents mixer from running before tank is full — process interlock.
03
TON timer DN bit both stops the mixer and triggers drain, creating automatic handoff between mix and discharge phases.
Add a low-level sensor to stop the drain valve; add multiple fill valves with separate timers for multi-ingredient batches.
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