Nothing close enough? Start from a blank ladder logic → Describe it in one paragraph.
How to use a ladder logic template.
- 01Define tank instruments
List your level switches (LSL, LSH), temperature sensor, inlet valves (V1, V2), agitator motor (M1), and discharge valve (V3) with their PLC I/O addresses.
- 02Describe the batch sequence
Enter the recipe steps: fill ingredient A to LSH → close V1 → fill ingredient B to LSH → start agitator M1 → mix for 10 min → stop M1 → open discharge V3.
- 03Add safety interlocks
Specify conditions that must abort the batch — high-high level, over-temperature, agitator overload — and ChatDiagram adds these as NC contacts in a safety rung that de-energises all outputs.
- 04Review step transitions
Check that each step's done condition correctly enables the next rung — level-switch DNS, TON DN bits, or operator NEXT pushbutton.
- 05Export for validation
Download the diagram as PDF or PNG to include in your IQ/OQ validation pack or O&M manual.
Questions about ladder logic templates
How do I implement a timer-based mixing cycle in ladder logic?
Use a TON (Timer On-Delay) instruction. The rung enabling the TON is sealed in by the agitator RUN coil. When the accumulated value reaches the preset (e.g., 600 × 100 ms = 60 s), the DN bit energises a MIXING_DONE internal coil that closes the next transition rung and unlatches the agitator.
What is the correct way to handle level switch debouncing in batch logic?
Mechanical float switches can chatter on turbulent surfaces. A common fix is a small TON (0.5–2 s preset) in series with the level switch contact; only when the switch has been continuously active for that preset does the DN bit trigger the transition. This prevents false advances mid-fill.
How do I add a second ingredient to a batch mixing ladder program?
After the first ingredient reaches its target level and the inlet valve closes, a new rung examines the STEP_1_DONE internal bit and energises the second inlet valve (V2). A separate level switch (or the same LSH after a short drain) signals the second fill is complete, advancing to the agitation step.
Can batch mixing ladder logic comply with ISA-88 batch standards?
Yes — ISA-88 organises batch control into Procedure, Unit Procedure, Operation, and Phase layers. A PLC ladder program typically implements the Phase layer (individual equipment actions like FILL or MIX). The higher layers can run in a SCADA/DCS that sends phase commands to the PLC via data registers.