Michael Lloyd

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About Michael Lloyd

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  • Birthday 06/01/58

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  • Gender Male
  • Location Texas
  • Country United States
  • Interests Photography, Long Range Shooting, Reloading, Fishing, Hunting

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  1. WIFI Communication to RIO

    I think the link was for hardware that you could use to set up the WiFi network.  I probably work in a different industry than you do. We wouldn't use remote IO on a WiFi network unless failure of the link combined with failure mode of the card would absolutely never cause an unsafe condition. That said, I put some point IO on some water pumping stations. The IO was for monitoring and control of stations that were a couple of miles away from the controller. Comm was via an iNet radio and ethernet cards in the racks on each end. The remote IO looked like any other ethernet IO rack in the facility. It worked great with one little exception. When I put the system in it was fall. The trees didn't have leaves on them. When spring came the remote rack communication dropped out. We had to raise the antennas above the height of the trees. Apparently pine trees attenuate a 900MHz radio signal. :o) It was a good lesson. We picked an easy antenna height vs climbing to the top of the tower and putting it there. If anyone is interested, the field based water pumps filled a tank at the station and then high pressure (2,000 psi-ish discharge pressure) pumps took suction from the tank and pushed the water into storage caverns to displace ethane, propane, or butane (not mixed, there were individual caverns, out of the salt cavern and into a pipeline. Technically the field water wells were not required for safe operation so point IO worked. 
  2. 1746-INT4 Used for Position

    One of the things that I like about this forum is I get a little insight into how other industries use PLC's.  I forgot the 3rd party modules for SLC's look like standard SLC modules but have very different function.  
  3. 1746-INT4 Used for Position

    Are you sure about the model number? That's an isolated thermocouple module for a SLC500 and I can't imagine how that would be used for position sensing. That doesn't mean it can't be though. What is an LDT? Acronyms don't cross over well from industry to industry (something I have to remind  myself of often)
  4. Why are there two posts with the same content 1 minute apart from one another?
  5. I don't use SFC's. I see the usefulness but not in the things I do. However, I found this online- To use a subroutine to control a transition, include an End Of Transition (EOT) instruction in the subroutine. The EOT instruction returns the state of the conditions to the transition.
  6. How to move an Array ? (CompactLogix)

  7. FactoryTalk - One button cannot be opened on SCADA

    I have one last idea - Is there a password in the system or on the button that would disable running scripts or VB?
  8. How to move an Array ? (CompactLogix)

    The CLX Instruction list is pretty handy. I don't have access to it right now but I think the Copy instruction is what you are looking for. CPY if I'm not mistaken
  9. FactoryTalk - One button cannot be opened on SCADA

    If there is an "invisible box" you should be able to select it by clicking in the area that contains the box. I've used the "invisible box" method to place a button with password permissions behind the visible button then use scripting to make it active (on top) when someone logs in with the correct password. 
  10. FactoryTalk - One button cannot be opened on SCADA

    It could be  that the button "lives" on top of an invisible area that has the "on button down" code attached to it.
  11. Introduction, new to fourm

    I saved these to Dropbox so I can look at them when I get back to the hotel. Who doesn't like a model train? :o)  I'll be interested to see what you've come up with. 
  12. pid tuning

    What PID parameters are you using? Also - smoothing the process variable isn't a bad idea but 3s is a very long lag time. You've probably changed the PV to a square wave (not good) so every three seconds the process is destabilized  If you're getting a lot of oscillation it'll be the tuning.Specifically the gain (if I and D are not set too fast, or on the case of D, it shouldn't be enabled at all) Derivative is typically not used for a level control process. Integral is typically set to return the PV to the SP but for level you want the time to be fairly large. Integral does not "like" oscillation in the PV, even if it's high frequency.  Your output swings tell me that the gain is set too high.  The business that I'm in is a little different than yours (I think, I'm in oil and gas processing) but I can give you an example of how I would tune a level control. There are equations, slide rules, formulas and probably even a little black magic that you can use. I've used many different ways to tune but this is how I like to tune simple processes like level. This will be specific to level: Derivative - not needed. There is a value to set derivative to in the AB that negates the effect but it's been awhile and I don't recall what it is Integral - If I remember right the units for the CLX PLC PID loop is minutes per repeat. You'll initially set this to a high value. 20 minutes. Especially if the level is noisy (trend it and see how much it moves. Be aware of high frequency oscillations, large or small) Gain - A gain of 1 is a good place to start but in this case you already have a value that isn't working for you. Start there. If you can trend the SP, PV, and output while you are changing the Gain it'll help you visualize what's going on. As you increase gain the loop gets more sensitive. Ie the amount of level deviation from setpoint has a greater affect on output. It sounds to me like the gain is set too high. Decrease the value. You actually have two goals here- decrease the amount of output swing and maintain the level within the boundaries that the process can withstand. Level is very often mistuned imho (including by me). You have a "volume bottle", ie the pool of water. Typically level does not have to be controlled to exactly X%. There is a range, say 40% - 60% that the process can handle. Maybe it's 45% - 55%... The point is that you can allow swings in the PV as long as the level is maintained within the limits that are allowed. For large surge drums (in our industry, that could be 30% - 70%. We don't care if it is specifically at some value, say 50%, just that it doesn't over fill or run dry. Back to tuning - Double check that I is set to I relatively high time value and D is disabled. Decrease the gain while watching the output and the PV. As you decrease the gain (slow the loop down) the output swings should start to diminish. At some point things should settle down. Decrease it just a little from there. Watch the loop SP, PV, and output for a bit. Don't worry about SP and PV matching for now. Once you settle the loop down you can slowly decrease integral time and PV / SP should start to come together. If you set I too fast you'll destabilize the loop. Normally (other than level) you might want to adjust I until the loop destabilizes then slow it down about 1/2 way back to where you started. Then decrease the time until it destabilizes and go 1/2 way back to the new setting. At some point you'll find a place that the process likes You don't want to see a lot of output swings on level. The purpose of the level storage "vessel" is to add capacity to the system to help smooth out the swings. If you're familiar with C power supply design you know that capacitance is used to smooth out the ripple of the rectified AC. Same thing. Sort of This is pretty decent: http://cats-fs.rpi.edu/~wenj/ECSE446S05/pidtuningguide.pdf Old school tuning setup: http://www.eng.utoledo.edu/~wevans/chap19_S.pdf https://literature.rockwellautomation.com/idc/groups/literature/documents/wp/logix-wp008_-en-p.pdf  
  13. CompactLogix

    There are a number of free pieces of software out there that will let you scan a network and tell you what device has what IP. address. If your laptop and the PLC are the only devices on the network it’s pretty easy to figure out what the PLC IP is.  Angry IP Scanner (I know, weird name but it works) is simple but you would need to know the subnet mask and subnet of the PLC. So that’s no help Wireshark is the better option in this case. Connect your laptop and PLC to a switch, let Wireshark run for a bit, there should be two IP addresses in the list of data      
  14. RSLogix5 Analog Scaling

    Just for clarity for me- is this for a PLC 5?    I can't help with a PLC5 other than help replace it with something from this century :o) SLC 500 or CLX... no problem
  15. Index Tag Names though AOI

    Sorry, I've been travelling. I'll attach one of the programs that uses what your looking for to this. It moves a bunch of data to/from an analog alarm block. I've used it up to almost 300 analog points with multiple parameters in each analog tag (using UDT's) so I know it's fast and pretty robust (ie it works) There is an AOI involved- AALM (I don't like the AB alarm block so I rolled my own. Theirs has too much crap for my purposes) And the routine you're interested in is AA_C  and maybe AA just to get an idea for what it's doing. AIOM is where I map an analog card point to a tag   Asherton_12_22_15.ACD