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. Tuning PID - how to do it properly

    You're very welcome. I finally got to practice what I preach today. They made me a mangler some years ago and basically ruined my life  but every now and then I get to have some fun and write a program or tune a controller. Today we tuned a still reflux accumulator level that was doing a great job at holding level but the flow out was a long period sine wave. Not good for process stability. During the process I was reminded of something that I planned to come here and share with you so I'm glad that you replied. In the PIDE setup you get to choose the equation type, Dependent vs Independent. Either works but Choosing Dependent makes the Integral units minutes/repeat (minutes per repeat) and that, to me, is a much simpler term to tune with. They basically mean the same thing but thinking in terms of time vs 1/T (repeats per minute) is just more intuitive (again, to me). I did some training today and when we switched our troublesome loop to Dependent it made more sense to the people involved.    
  2. Tuning PID - how to do it properly

    I think the whole article that the numbers above came from would have some use to others so I attached it. Level: Just to qualify things a little, level can be a little tricky. If the transmitter measures actual level then Gain = 1.0 works, sort of. If it's an old displacer type device and the specific gravity of the fluid is anything but 1 then the starting value of 1 is going to be too high. If the S.G. = 0.6 then about 60% is a good start. Too many times I've seen (and done it actually) where a level controller is tuned to hold an exact level. In the gas processing industry, that's not what you want to do. A little swing in the level with a fairly steady flow out is fine. The idea is to let the vessel take the surge (up or down) and to tune the level controller such that it shuts off at the appropriate low level point and has 100% output at the appropriate high level point, preferably below the LSHH (High level shutdown). I've seen quite a few plants go from unstable to stabilized just by tuning the level controls on various vessels correctly.     Initial Settings For PID Controllers.pdf
  3. Tuning PID - how to do it properly

    The process needs to be running before you can tune the controller. There a lot of ways to tune. Ziegler-Nichols calculations as well as others. I prefer the method I learned when controls were mostly pneumatic <--- :/ I feel like I need to get a cane.. Sometimes the integral units are in repeats per min. It's just he inverse of time. 1/Ts =  Repeats or 1/ repeats = time in seconds Sometimes the controllers don't use gain. They use percent proportional band instead. Same drill, one is the inverse of the other. For two mode controllers, set Integral time out of the way, like 10m - 20m in the Logix PLC (units are in minutes). Then increase gain (1 = 100% PB, 2 = 50% PB, etc) until the process starts to oscillate. Lets say you started at 1 and at 3 it started oscillating, set it back to 2. BTW - each gain change should be followed by a "bump". Like change the setpoint slightly. If you want to to tighten it up further, increase until it oscillates (after a bump). Then back off to 1/2 way between 2 and 3. Once you get that where you like it, speed up (lower) integral time until the process oscillates after a bump, rinse repeat. Integral time adjustment will affect gain so you may find yourself reducing gain at some point. These are a good start. For speed you can use flow for an initial starting point. PID Default Startup Values Process Variable K (Gain) Ti (Integral Time, min.)  Td (Derivative Time, min.) Flow 0.8 0.2 0.0 Level 1.0 10 0.0 Pressure 2.0 0.5 0.0 Temperature 1.0 3.0 0.2  
  4. PLC5 to RS Logix5000 advice needed

    That's where we are with our PLC 5's. They work, we have parts, we have software, so leave them alone :)
  5. PLC5 to RS Logix5000 advice needed

    I'm pretty sure you can get a Windows version of PLC 5 software. That and a new computer is probably your cheapest and safest option. I have a coworker that was primarily a GE guy (urp) when we hired him but he was able to make changes and link our HMI software (ClearSCADA) to it with minimal issues. PLC5's aren't bad. It's just that parts are getting hard to come by and compared to the "new" IEC programming software and PLC's, they aren't as functional. They were quite the hot rod in their time. Kind of like the Square D box. You could talk that thing into doing just about anything... I've never programmed PLC5. I've only replaced them due to obsolescence. We have a lot of them where I'm working now and we have (tons of) spare cards, processors, etc. We also have people that can get in and do the work you described (force bits, troubleshoot) so I doubt I'll see a conversion done here.
  6. PLC5 to RS Logix5000 advice needed

    I used some Windows based software from these guys: http://www.fast-soft.com/page.php?21&gclid=CjwKCAjwtuLrBRAlEiwAPVcZBjrqoOEZyeIBfTwEFTRy_OKEoiW9mBQJS9Hpz0oGZp5ts8o-VbOuLBoCOPsQAvD_BwE At the time we were doing a lot of work with the Siemens TI-505 and Siemens S7 PLC's and someone in corporate specified "Siemens PLC" for a water treating package. We used Fast-Soft Softworks for the TI-505. The vendor supplied an S5. It was an interesting little box. The logic was literally a mix of ladder and statement list. They had to use STL commands (that coexisted in the rung structure) because there was no ladder for that function (and sometimes I think they were just showing off :) ) I initially thought that the Fast-Soft software for the S5 would look the same as the TI-505 but that didn't happen lol
  7. PLC5 to RS Logix5000 advice needed

    Or Siemens S5 (I actually liked those but it's been a while)
  8. PLC5 to RS Logix5000 advice needed

    I read and replied on my phone so I probably didn't do the best with understanding the scope of the OP's problem. Floppy drives? DOS? Holy vintage computing Batman!
  9. PLC5 to RS Logix5000 advice needed

    Are you planning to replace all of the PLC 5 hardware (processors and IO cards)? If not, converting the software so that you can open it in Logix 5000 isn’t going to do anything for you (except make a god awful ungainly program that’ll be hard to follow). 
  10. Micro850

    I'm just going to answer both posts here. Yes, yes Don't expect that thing to program anything like RS500 
  11. Ethernet IP

    I love the net-eni's, said nobody that ever put a Micrologix on a half dozen platforms in the GOM and expected a Freewave radio to maintain a good link in the fog at max range. Someone before me installed them and someone after me replaced them all with Micrologix with ethernet ports :)
  12. Is it possible to communicate PLC's with different ip range?

    We used the gateway address in everything. Some devices required it. It was a Class B network with a fairly common subnet. It's probably getting close to requiring a different subnet. Come to think of it, they recently moved controls off of the corporate NW so it's probably already changed. Either way, everything is routed, tunneled, and pummeled so the Russians can't get in, unless they want to.  
  13. PIDE instruction help in water blending application

    Or you could simple roll your own. It's just water... THQH + TC QC = Tfinal(QH + QC) T = Temperature. Doesn't matter what units as long as they are the same. Q = Flow rate. Doesn't matter what units as long as they are the same. I might add a bias value to the AOI to allow me to tweak the output plus or minus x% Or you could spend a bunch of time trying to make a Multivariable Control block do what most modern shower controls do with little to no effort. The MMC is a block used in advanced control applications where inter-controller interactions wreak havoc on the ability to control the process. It's not intended for making hot water... The 667-YD Fisher control valve is tailor made for this application (it's the part about the first drawing that was missing and that was bugging me). product-bulletin-fisher-yd-ys-control-valves-en-125150.pdf
  14. Learning about MicroLogix 1500

    It's better than  than the Micro 850 unless your need something to throw on the fire to keep yourself warm. I think the Micro850 would be better in that case.
  15. Learning about MicroLogix 1500

    This is one that bites fairly often...