Nothing close enough? Start from a blank ladder logic → Describe it in one paragraph.
How to use a ladder logic template.
- 01Describe your intersection
Type your sequence in plain English, e.g. 'Three-phase traffic light: 30 s green, 5 s amber, 30 s red, repeat. Add pedestrian button input that extends red.'
- 02Review the generated rungs
ChatDiagram produces TON timer rungs, output coils for GREEN/AMBER/RED indicators, and latch/unlatch logic for the pedestrian override. Check that rung order matches your intended scan sequence.
- 03Annotate inputs and outputs
Rename I/O addresses to match your PLC (e.g. I0.0 for the push-button, Q0.0–Q0.2 for the lights) using the inline editor.
- 04Export or share
Download the diagram as a PNG for your lab report, or copy the sharable link to embed in your LMS or email to your instructor.
Questions about ladder logic templates
What timer instructions are used in a traffic light ladder diagram?
Most traffic light ladder programs use TON (Timer On-Delay) instructions. One TON per phase accumulates time; when the preset is reached, its done bit (DN) enables the next rung, resets the current timer, and energises the next output coil. Some designs use a single recycling TON with comparison contacts to switch phases.
How do I add a pedestrian push-button to the ladder program?
Map the button to an input bit (e.g. I0.3). Add a rung that examines-on I0.3 and sets an internal bit (M0.0). In the RED timer rung, include M0.0 as a series contact that extends the preset value, or adds an extra TON stage before returning to GREEN.
Can I use these diagrams with Allen-Bradley, Siemens, or Mitsubishi PLCs?
The ladder logic structure is IEC 61131-3 compliant and the concepts transfer across all major PLC brands. You will need to adapt the I/O addressing syntax — for example, %I0.0 in Siemens versus I:0/0 in Allen-Bradley — but the rung logic is identical.
Is a traffic light ladder diagram a good PLC exam topic?
Yes — it appears in TAFE, City & Guilds, and NZQA automation assessments because it covers timer usage, sequential output control, and input conditioning in a compact program. Examiners often ask students to extend it with a fault indicator or a night-mode flasher.