Issue with Conveyor Bit and One Shot in RSLogix Emulate

PLC (Programmable Logic Controllers)
1

Issue with Conveyor Bit and One Shot in RSLogix Emulate

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I’m encountering an issue with my control logic in RSLogix Emulate, and I’m hoping to get some insights. Here’s the situation:

When my proximity bit is energized, it triggers an interrupt due to the one shot instruction. This works as expected, with the interrupt being triggered only once.

However, I expect that when I energize the level bit, the conveyor bit should energize again. My understanding is that even though the proximity bit remains energized, the conveyor trigger interrupt bit should be de-energized because the one shot only energizes it for one cycle.

The problem I’m facing is that when I run this in RSLogix Emulate, energizing the level bit doesn’t result in the conveyor bit being energized.

Can someone help me understand why this is happening and how I can resolve it? Any advice or suggestions would be greatly appreciated!

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I’ve taken a look at your ladder logic and I think I can help clarify what’s going on. From my experience, the behavior you’re seeing is due to how the one shot (ONS) instructions work in combination with the logic in your rungs.

Key Points to Consider

One Shot (ONS) Behavior

  • The one shot instruction (ONS) ensures that an output is energized for only one scan cycle when the input condition transitions from false to true.
  • Once the one shot has fired, it won’t trigger again until the input condition goes false and then true again.

Logic Flow in Your Diagram

  • Rung 0000: The level bit (B3:0/1) triggers the ONS (B3:0/7), which sets the conveyor trigger (B3:0/8).
  • Rung 0001: The proximity bit (B3:0/0) triggers the ONS (B3:0/11), which also sets the conveyor trigger (B3:0/8) and the conveyor trigger interrupt (B3:0/10).
  • Rung 0002: Seems redundant with another proximity bit and ONS (B3:0/9), but this doesn’t affect the conveyor trigger directly.
  • Rung 0003: The conveyor trigger (B3:0/8) and conveyor trigger interrupt (B3:0/10) must both be true to energize the conveyor bit (B3:0/4).

Why Your Conveyor Bit Isn’t Energizing

Energizing the Level Bit

When you energize the level bit (B3:0/1), the ONS (B3:0/7) sets the conveyor trigger (B3:0/8).

  • However, this alone isn’t enough to energize the conveyor bit (B3:0/4) because rung 0003 requires both the conveyor trigger (B3:0/8) and the conveyor trigger interrupt (B3:0/10) to be true.

Proximity Bit State

  • When the proximity bit (B3:0/0) is already energized, the ONS (B3:0/11) will not trigger again unless B3:0/0 goes false and then true again.
  • Therefore, the conveyor trigger interrupt (B3:0/10) isn’t being set again when you only energize the level bit (B3:0/1).

Potential Solution

Reset Logic

  • Ensure there’s a way to reset the conveyor trigger interrupt (B3:0/10) after it has been used. This can be done by adding a reset condition based on your process requirements.

Modify Rung 0003

  • Consider revising rung 0003 so that the conveyor bit (B3:0/4) can be energized by the conveyor trigger (B3:0/8) alone if that fits your logic requirements.

Your current logic requires both B3:0/8 and B3:0/10 to be true to energize the conveyor bit (B3:0/4). Since B3:0/10 is controlled by the proximity bit and its one shot, it won’t retrigger unless the proximity bit state changes. Adjusting your logic to better handle these states should resolve your issue.

Hope this helps! Let me know if you need further assistance.