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| 3/6/2011 12:53 PM | |
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Posts: 14 Rating:
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Hi all, Find attached a program I wrote for my groundsource heatpump. Everything seems to be working fine except my two pi controlers which I cannot get working. These pi controllers work fine when simulated, but when run on the system they do not respond at all..If anyone can help me just to get the pi controller working in heating modethat would be phenomenal. I have two pt100 sensors coupled to a Logo RTD module,on the input and output pipes on the water side of the heatpump. The water pump is inverter driven, with a 0-10V output from logo to command it. When the heatpump is in heating mode I want the water pump to be running at a miniumumwater flow rate, but I want the pi controller to start increasing the flow rate on the pump when the temperature difference starts to gotoward a setpoint of -2 degrees centigrade. The following has been setup:- The two temperature sensors are inputed on blocksAI5 and AI6, wherethe analog amplifiers (B002, B010)are used to offset the error in the sneosrs. The analoge comparator (B006)monitors the temp diffrence and switches beween cooling and heating mode. An analogue math block (B016)is used to calculate the temperature difference from the analogue amplifiers. This value is then inputed into the pi block (B037) The pi's output value is thenpassed through another analogue math block (B041) and an analogue ramp block (B045), before being outputted as a (0-10V) output at AQ1 to the inverter. Good luckwith this one, Adam AttachmentHelp.zip (438 Downloads) |
Last edited by: Newbeee at: 3/6/2011 3:57 PMLast edited by: Newbeee at: 3/6/2011 3:30 PM |
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| 3/7/2011 4:36 PM | |
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Posts: 14 Rating:
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Hi Marcjan, I am in work so I probably shouldn't be messaging you, but this problem is playing on my mind. I have attached the full program for my heat pump, showing youall of the inputs. I hear what you are saying about I8, which is being used as a digital input. In fact all of the base modules inputs are being used as digital ones. I believe the physical layout of my logo modules with regards to possible analogue inputs is as follows:- base module>analogue input module>RTD input module. I will have to check this after work though. With regards to the properties option, I left that selected as 2AI's as I am not using theinputs on the base module as analogue ones.That is why I used inputs AI5 and AI6; would I have been correct in doing so? Thankyou once again, Adam Attachmenttest.zip (384 Downloads) |
Last edited by: Newbeee at: 3/7/2011 4:41 PM |
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| 3/7/2011 10:05 PM | |
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Posts: 14 Rating:
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Hi Marcjan, Ok, I have ventured down to the pump room, and I run an online test showing all the analogue input connection values. I was correct in thinking the inputs I needed were AI5 and AI6, as they are showing the temperature values. I have attached three images, one of the computer screenshot and two of the enclosure which shows my logo layout. Any other ideas? I have tried and tried to resolve this problem for ages and I am an engineer myself and it's making me look stupid, lol. Thanks again, Adam Attachmentpics.zip (365 Downloads) |
| 3/8/2011 12:11 PM | |
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Posts: 14 Rating:
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Hi Marcjan, I have had a thought.. I have inputted the values for both the integration time a gain value by double clicking on the function block and editing it in the window that pops up. However I noticed that when I go into Edit>Block Properties (All Blocks), both values aren't entered. (I have attached the screenshots so you can see for yourself.)So could it be a software fault even though I have made sure the Logo soft is fully up to date? If this is the case, would it be possible to edit the 'parameters' of both the gain and integration time of the PIthrough the Logo TD I have installed.. Cheers, Adam Attachmentpics.zip (348 Downloads) |
| 3/8/2011 12:57 PM | |
Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating:
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You can show and edit all parameters of the PID and that is a good thing to do to find your problem. Make a new screen( or more) with your PID parameters and test again, now you can see what's happening and adjust parameters realtime. I have attached your first file with a menu structure for the screens on your td. Menu stucture ilearned here: https://www.automation.siemens.com/mcms/programmable-logic-controller/en/logic-module-logo/application-examples/Pages/Default.aspx Verry usefull site ! Now you can monitor as much variables as youlike to trace the problem. Not all screens are filled yet, just a example AttachmentHelp3.zip (373 Downloads) |
Last edited by: Marcjan at: 3/8/2011 4:18 PMProblem solved? |
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