If you're working with MicroLogix 5000 and want to understand how to keep an output ON even after releasing the button, you need to learn about Latch (L) and Unlatch (U) commands. In this post, I’ll explain these concepts in a simple, beginner-friendly way.
What is the Latch (L) Command?
The Latch command is like a memory switch. Once you turn something ON using a push button, it stays ON until another command turns it OFF.
🔹 Example: Imagine pressing a switch to turn ON a lamp. The lamp remains ON even after you remove your hand from the switch.
How to Use Latch in MicroLogix 5000?
- Add a Start Push Button (NO) in the rung.
- Add a Latch coil (L) and assign a tag to the Lamp.
- When you press the start button, the lamp turns ON and stays ON.
What is the Unlatch (U) Command?
The Unlatch command turns OFF a latched output when activated.
🔹 Example: If a lamp is ON and you press a Stop button, it turns OFF and stays OFF.
How to Use Unlatch in MicroLogix 5000?
- Add a Stop Push Button (NO) in a separate rung.
- Add an Unlatch coil (U) and assign the same lamp tag.
- When you press the stop button, the lamp turns OFF.
Testing the Program in MicroLogix 5000
✅ After writing the logic, go to WHO ACTIVE, select the PLC, and download the program.
✅ Now, press Start → Lamp turns ON (Latch).
✅ Press Stop → Lamp turns OFF (Unlatch).
This is how you can use Latch and Unlatch commands in your PLC programming!
Conclusion
🔹 Latch keeps the output ON until Unlatch turns it OFF.
🔹 Useful for motors, lamps, and memory-based controls in PLC.
🔹 Simple and easy to implement in MicroLogix 5000!
If you found this helpful, stay tuned for more PLC tutorials! 🚀
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