adccommunitymod (AutomationDirect) asked a question.
Created Date: April 24,2018
Created By: Jaycen
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I'm trying to write a latch circuit that includes an HMI toggle button. When I toggle the button off, I'd like to break the latch. It doesn't look like you can map a tag to each button state, so I'm looking for a way to do this in logic. I thought I could add a rung immediately below my latch that calls a Trailing Edge One Shot contact that would turn on an internal bit. I then put a NC contact from that bit upstream from the HMI button and latch. Only, it doesn't unlatch the rung. What am I missing?
Created Date: April 24,2018
Created by: Jaycen
I'm trying to write a latch circuit that includes an HMI toggle button. When I toggle the button off, I'd like to break the latch. It doesn't look like you can map a tag to each button state, so I'm looking for a way to do this in logic.
I thought I could add a rung immediately below my latch that calls a Trailing Edge One Shot contact that would turn on an internal bit. I then put a NC contact from that bit upstream from the HMI button and latch. Only, it doesn't unlatch the rung.
What am I missing?
Created Date: April 24,2018
Created by: bcarlton
Just place the contact from the HMI button after the branch containing the latching contact. If the HMI button is the only condition initiating the latch rung then you don't even need a latch.
Created Date: April 24,2018
Created by: Jaycen
I attached a screenshot of the logic. Right now, it's the only thing in the rung, but that's because I'm trying to learn something new. There will be more upstream permissives.
Created Date: April 24,2018
Created by: Jaycen
I figured it out. I had to put the Trailing Edge One-Shot into a rung before my latching rung. I think it has to do with the timing of how scans are executed.
Created Date: April 25,2018
Created by: a agnone
Little confused what you are doing with a latch. So you toggle the PB off from the HMI? You can control the toggle directly from the PLC. If your PB tag is C0 for example, you can do a reset to un-toggle the PB or do a set to toggle it on. I usually toggle on and for instance I press E-Stop or some other condition I can do a one shot reset C0 to turn off the PB. sounds like somewhere the PB
Created Date: April 25,2018
Created by: a agnone
is being turned on.
Created Date: April 25,2018
Created by: Jaycen
Little confused what you are doing with a latch. So you toggle the PB off from the HMI? You can control the toggle directly from the PLC. If your PB tag is C0 for example, you can do a reset to un-toggle the PB or do a set to toggle it on. I usually toggle on and for instance I press E-Stop or some other condition I can do a one shot reset C0 to turn off the PB. sounds like somewhere the PB
Hi, a agnone. I'm new to the Koyo PLC. How do you set/reset a bit like that?
Created Date: April 25,2018
Created by: Jaycen
Actually, I 've run into a new issue using the toggle push buttons on the HMI. I can use them to latch/unlatch a rung in the PLC, but now I'm running into problems with upstream permissives.
If I have a rung where the toggle PB on the HMI initiates the latch, but an upstream permissive won't allow the rung to actually latch in, I need to toggle the PB back to it's "off " state.
Created Date: April 25,2018
Created by: a agnone
Well, for example, if you created a HMI button using tag "Chain Off " and assigned C10 to it you can control it in the plc. Looks like you assigned "Toggle " to it. So once you press the HMI push button C10 toggles on and stays on. You can either press the HMI button again and it will go off, or somewhere in your program you and do a one-shot reset on C10 and the toggle Push button will go off.
Try assigning "Momentary " to the HMI push button. That might be what you are looking for. Put NOT C10 in line with the rung and when someone pushes the HMI button, C10 will go high momentarily and unlatch the output. Toggled HMI push buttons can be tricky sometimes because they stay "on " until pressed again or somehow reset within the program.
Created Date: April 25,2018
Created by: Jaycen
Thanks, a agnone. I tried the RESET coil and found that very helpful. I like the toggle buttons a lot. Using a single button instead of two with an indicator seems more efficient to me.