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Found 20 results

  1. Simple PID loop

    Hi , I have been working with the PID loop and it seems very complicated. I just want a simple PID loop (I'm anti auto tune) with manual mode (straight output) and automatic mode (with manual tuning) and I've seen posts that seem to imply that this can be done. Would I used the Run PID function? Or set the parameters in the config struct, Load PID AutoTune Data, then save it? and then Run PID? Would I use the PID AT Params or PID_Config struct or both? I only need a PI controller - so would I need to set SP, PV, P, I, Control Valve, Reverse Action (Does this account for a negative sign in the PI values?), and what else is mandatory at a minimum? Do I need Sample Time, and the Input and Output Highs and Lows? Is there a better way?
  2. PID struct retain

    I am trying to retain the values of a PID structure but I do not know how to do it. Any ideas? Thank you.
  3. PID Autotune Status -13

    Hey there, I'm trying to set up a PID loop for a fan, and when I run autotune I don't get any control value and I get a status of -13. I have the set point and upper and lower limits set. I can't find any reference to a -13 status anywhere, can anyone help me out? Thanks in advance!
  4. Hello there! I'm trying to drive DC Motor with PLC V570 via PWM. This is for my diploma thesis so I want to do it nice and design PID controller in Simulink Matlab. In PLC I want to do identification of the transfer function for this system with step response. This is the first order system, so it shouldn't be a problem. Than I'm going to use this transfer function in Simulink to find PID parameters. At the end, I got P,I and D parameters from Simulink, and I don't know to transfer them into PLC. For example for closed loop system with discrete PI controller in ideal form P(1 + I*Ts*1/ (z-1)) (Serial PI) I have P = 1.93, I= 1.86[sec] Ts = 0.1[sec] Than in PLC I got Sample Time = Ts = 0.1[sec] = 10 Integral time = I= 1.86[sec] = 2, because it is defined in units of 1 second, Proportional band =(1/P)*100% =51.81% = 518 defined in units of 0.1% Am I doing this right? Could anyone please tell me what is the type of transfer function for PID controller is used in PLC Vision V570 (Serial or parallel)? And how do I correctly transfer parameters P, I, D into PID regulator in PLC. Thank you.
  5. Hello everyone, does anyone know how the PID autotune function works? Is it using a method like "Ziegler-Nichols"? I have tried to use the autotune function. It delivers values for Kp, Ti and Td. But when using this parameters for process, the way how it tunes is worser than worse ............. Is there any additional documentation for PID available? The integrated help of UniLogic is very rare.......
  6. Hello, I got the task to make a control system for a air conditioning unit which I guess needs 4 PID loops. One each for heating, cooling, humidification and dehumidification. Only two loops will be active at the same time. The product overview for Samba SM35-J-TA22 say "Auto-tune PID, 2 independent loops ". Does this mean that it is not possible to have 4 loops in the program? I would appreciate a quick reply!
  7. PID question

    I am wondering about how the internal settings of the pid works. We have a process that needs to bee kept as close as possible to 85°C with a maximum og 90° and minimum of 80° this is a steam tupe heater which has an internal pipe with some fluid pumped through. The steam and the fluid enters at the same end and at the other end we have our temperature sensor that gives us the process value the steam is controlled by a valve controlled by 4-20 mA. The process fluctuates around 8° wich is considered to much. there are some other variables that affect this process which is best described as the temperature drops by a few degrees with some minutes a part. I am adding a new window where I can set the high and low value of the pid output range . So hopefully that will minimise the fluctuation a bit. But I keep thinking about the Input range. (process value low limit and high limit) I have these values set as 0 for the low limit and 1000 for the high limit = 0-100°C same as the range of the pt100. Should I rather set these values as the lowest value and highest value that we want. 800-900 (80° - 90°) I would really appreciate some help here. Best regards Bæring
  8. 20160322 103121

    From the album SOLARHARWEST

    heatexchanger using a Samba 4.3 for dual pid control of oil and water pump's,and run signal for gps sun tracker, fresnel lens is not attached yet
  9. I am working on a large Kiln. We are trying to create recipes for the Kiln to process burn rates. We have many recipes but I can work with that. What we need to do is set the top temp (let say 1800 deg) and have it climb at a certain rate (lets say 300 deg per hour). I have been looking at the PID but I can only see what it can raise strait up to the degree set and stay there but be steady. I would more need to reset the PID after each hour for 6 hours to get it to smooth out but even that would be wrong because it would climb strait to 300 degrees and ride there until the hour was up. We really need it to take the hour to get to 300 degrees, then take an hour to get to 600 degrees and so on until it gets to 1800 deg. Once there we will want it to hold for a time and then descend at a certain rate as well. Does anyone have a Kiln program that we can refer to? I can write a real large program that will do this breaking it down to each minute (Like 5 degrees per minute only) but figure there is a better way. Any help would be appreciated.
  10. Hi all I am new to the Visilogic PLC platform and I have a PID question. A little background on myself: I have been using Allen Bradley / Rockwell products for the last 25 years and it is now time to change to a new platform. The company that I work for will not buy in to the licence fees associated with their products, so here we are trying out Unilogics products. My first project is a heat tunnel application using a V570-57-T20B controller. I also plan on using a snap in I/O module to allow the use of a type J thermocouple. My question is this: I have set up the PID FB configuration. No problem. Now I want to incorporate the auto tune FB for the same PID loop. Must I configure the Auto Tune FB since the PID FB is configured? If so, do I use the same MI and MB in both configurations, or does the Auto Tune FB configuration need to have it's own MI and MB's? It seems to me that they would both need to use the same memory addresses. I have read through the manuals that I could find and watched a few vids on Youtube and I suspect that these are using older software revs. Also, do I really need to have the snap in I/O? There is enough I/O on the controller for this application. If I can use my J thermocouple some way without having to buy the snap in I/O, that would save me some bucks. My hardware is on order and not here yet and I have nothing to download to and experiment with. I have enjoyed using the Visilogic software so far. Thanks
  11. Background I'm working on updating some of our test equipment. The current setup uses two 20 gallon vacuum reservoir tanks, two manual needle valves per tank, 4 solenoids for tank vacuum controls, 2 differential pressure controllers with DC output, and one PLC. It also uses a very manual process for setup. My goal is to replace the main control box with two analog proportioning valves, 2 analog pressure transmitters, and one PLC with the PLC controlling the vacuum levels inside the tank automatically through data tables. I have a slightly different setup in testing right now but I'd like to get a finer control. Question What's the best way to control the process variables for two regulators using PID without creating a feedback loop and oscillation? One Valve would function as a cooling type PID (Reducing the vacuum level based on input), one valve would function as heating (Increasing the vacuum based on input)
  12. Thank you for the webinar video about PID, was immensely helpful for a project I'm working on. Would it be possible to have a short webinar on PID with digital output only instead of analog out? I know there are some key differences and it would be helpful to see some examples.
  13. Are there any issues with calling PID configuration from something other than SB2 on startup to change the configuration without restarting the PLC? The desired end state is a v350 controlling two electronic regulators with different set points throughout the day.
  14. Hello all, I am working with V350-35-RA22 OPLC and am using the PID FBs to control temperature. I am controlling a heater with a solid state relay and using the PWM function block. The duty cycle of the function block is set to the output of the PID. I am running the auto-tune using the PID server tool and it is able to change the output of the PID. However, when I instead attempt to use the run autotune function block, the PID output remains at its minimum value. Is there any reason this would happen?
  15. Hi, I have to make logic were one PID loop controls two series-connected valves (look File 2). In logic, PID SP is temperature what comes from dynamical graph (depend on the external air temp), PV is outgoing temperature (after valves), PID CV is used to activate PLC relay outputs- OPEN, CLOSE (look File 1) There is no feedback from valves, from technical data is known that OPEN position to CLOSE position takes 150 sec (both valves are same type). Actions: 1. If its needed to raise water temperature, then its activated OPEN output, which is linked to valve "Direct" (look File 2, 11GM1). When valve "Direct" is full-open, but temp. isnt still high then end- switch Open will be electrically close valve "Bypass". 2. If its needed to lower water temperature, then its activated CLOSE output, which is linked to valve "Bypass" (look File 2, 11GM2). When valve "Bypass" is full-open, but temp. isnt still low then end- switch Open will be electrically close valve "Direct". First positions (physically) are , before PID Auto -tuning 40/60: "Direct" valve start position is 60% opened and "Bypass" valve start position is 40% opened (maybe 50/50 would be better?). I have looked U90 Ladder example "PID with motorized valve". It seemed very helpful, in example primary loop PID is looking SP-PV error and secondary loop compares PID CV and Virtual Valve Position. In example there is only one valve, how to do it with two valves what are series-connected? OK, in logic OPEN output is increasing "Direct" valve position and CLOSE output is increasing "Bypass" valve position, but what to do in logic when movement physically goes over to series-connected valve (look algorithm and File 2)? Ylle
  16. V570 PID

    This is my first post so I didn't have the time to introduce myself. Anyway I am starting my first project with a V570 and an snap in IO card in order to monitor and control the process of a drying oven. I viewed the corresponding webinars and I think I got the main idea about Visilogic (My previous knowledge about ladder and PLC programming is minimum). Anyway when I insert a configuration PID FB in my project and trying to compile the code, I get the error mesagge that PID Config is not supported by Color PLC or/and V130-33. Am I missing something too obvious ? Any help is welcome, Thanks in advance,
  17. In my application, I am trying to control a Peltier, or thermoelectric device. Would you help me understand the logic in the program I inherited? The program has two PID loops, one that outputs heat, and another that outputs cool. When heating, cooling is inhibited. Any suggestions on better ways to do this? Maybe a single PID with two outputs? Just in case, a peltier device has two sides, a main and a waste. When current is flows though one way, the main side gets colder and the waste side heats. When the polarity is reversed, the main side heats and the waste side cools.
  18. PID Help needed

    Hello again Thank you all for your recent help. I have certainly experienced a steep learning curve with Visilogic! I require some help with using a PID function to control the putput of one of my valves. The problem I have is that the valve is "chattering" when near to the setpoint, i.e opening and shutting very fast as the setpoint is reached. I need to slow down the operation of the output, the control does not need to be so precise - i.e control within +/- 3 mbar of the setpoint at 103 mbar, or only open again after 2 seconds of closing. I thought that I would use the PID function to sort this problem but I am really stuck. COuld anyone please help me in very simple terms, to show me how to implement the PID into my ladder? I am using MI 2 as a linearisation of a 4 to 20 mamp input ranged 0 to 1000 mbar. This is what I want to use as my process input. Set point is 103 mbar Control can be +/- 3 or 4 mbar Would like to control Output 8 with teh PID function. Thankyou in advance :)
  19. PID Woes

    I am using a 570 to control air temperature. I have a hot duct and cold duct in parallel with dampers 90 degrees offset on the same shaft such that when, for example, the hot duct is 100% open, the cold duct is 0% open; driven by an Oriental Motors Stepper with potentiometer positional feedback. A thermocouple provides the PV. I am using the PWM output from a V200 card to drive said stepper in a 2 wire config with one wire being enable, the other being direction. My problem is that except for the setpoint that is manually entered of course, all the parameters are zero. I know the PID won't work with zeros in all the parameter values. What are some reasons auto tune did not write the values to the table? I am running visilogic 9.5.0 I have also tried to find pre-written PID example routines and cannot find them under the help > example file. I also tried updating to no avail. In fact, when I click on examples, I get one folder that is "version 900" that has no PID example that I can find. Do example PID's exist? Also, is there any conversion that needs to take place between the PWM output and the stepper? I'm worried I'm in Unitronics "No man's land" as the folk I've talked to at Unitronics support who are consistently good about answering questions seem to have the reaction of family at the Thanksgiving table when the wayward relative pregnant with an illegitimate child is metioned. I can feel the loss of eye contact on the phone. Then when I don't see examples, it makes me wonder if Unitronics just doesn't do much with PID's? Thank you for ANY help you can offer! rookieprogrammer being baptized in fire
  20. (Sorry for my english) Hi, I have to drive the desired temperature X. In general, the matter would be trivial, if I had one device that generates me the temperature, but unfortunately it is not. I have available: 1 - unit # 1 heating device with analog input (high power - priority 2) 2 - unit # 2 in heating mode with analog input (low power - priority 1) 3 - unit # 3 in the heating mode of the digital input (on / off - priority 3) 4 - unit # 4 in the heating mode of the digital input (on / off - priority 4) 5 - unit # 2 in the cooling mode of the analog input (with low power, but under certain operating conditions - priority 1) 6 - unit # 3 in cooling high-power digital input (on / off - priority 2) 7 - unit # 4 in cooling high-power digital input (on / off - priority 3) All these devices can be operated at the same time, of course, only in one mode. For each device there are also relationships that allow their activation. Devices do not have consistent performance - it depends on many factors, which can not measure nor even guess. I wonder on how to control these devices depending on the value of PID CV (Control Value). The only idea that comes to my mind is to assign to some range of values ​​for the turn on of the devices. I just wonder if the PID will function OK and wonder what to do with the start and the level of "zero". If CV would -100% to 100% is rather negative control must be attached to cooling devices, and positive to heating devices. Zero disables all devices. I'm worried about controlling devices # 3 and # 4 - I can not turn on / off frequently - they are large chillers. Tonight I got the idea to control these problematic units. If the PID is saturated by X time I would turn on device #3. Where it will 2X - turn on device #3 and #4. Now I had to figure out a condition for the descent of these aggregates. I suspect also that I need to reset periodically PID saturation and add a sort of hysteresis to include these units. What do you think? Any ideas?