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Control 9 fan with pid control

Created by: Akhgari at: 5/27/2014 11:00 PM (11 Replies)

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5/27/2014 11:00 PM	Rate (0)
Akhgari Posts: 4 Rating: (0)	Hi I want to control temperture of cooling tower. in this situation I have 3 cooling tower and each them have 3 fans. All fans drive with inverter. now how can I use pid control for them?
Akhgari Posts: 4 Rating: (0)
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5/27/2014 11:06 PM	Rate (0)
Amit_86 Platinum Member Joined: 3/18/2008 Last visit: 12/8/2023 Posts: 1750 Rating: (272)	Akhgari Hi I want to control temperture of cooling tower. in this situation I have 3 cooling tower and each them have 3 fans. All fans drive with inverter. now how can I use pid control for them? Hello, PleasedownloadS7200 Manual from below link. S7-200 System Manual. Pleasesee Chapter 15 for PID Control. Also,Please look at this below tips. How to Use the PID Instruction Wizard (Tip 53) How to Use the PID Loop Instruction (Tip 54) Hope this helps.
	Last edited by: Amit_86 at: 5/27/2014 11:07 PM VANDE MATARAM.....
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5/28/2014 5:06 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Akhgari Hi I want to control temperture of cooling tower. in this situation I have 3 cooling tower and each them have 3 fans. All fans drive with inverter. now how can I use pid control for them? How the fan are connected with inverters? According to what signal will control the fans? How that signal is reading in CPU or in invertors? Are you sure the S7-200 CPU could handle that system? Best regards, Hristo Mihalev

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5/28/2014 8:06 AM	Rate (0)
William_B Posts: 5225 Rating: (1195)	UMENCHO Akhgari Hi I want to control temperture of cooling tower. in this situation I have 3 cooling tower and each them have 3 fans. All fans drive with inverter. now how can I use pid control for them? How the fan are connected with inverters? According to what signal will control the fans? How that signal is reading in CPU or in invertors? Are you sure the S7-200 CPU could handle that system? Best regards, Hristo Mihalev Dear Akhgari, Welcome to this forum. From your description it seems as though someone put the cooling towers together and you are asking from this forum to write the program for you. If this is not true.. help us help you. Please follow UMENCHO suggestions. Paint inside our minds what you have and what your planning was to do. Even a hand-phone photo of your hand sketches will be helpful. Please tell us what PLC hardware you were thinking of using. Giving us an idea of what your programming background is will also give us an idea where to start. There is no shame in being a beginner - if that is the case. But avoid shame by making us more than mentors guiding you. Please come back to us.. we'll be here to assist. Greetings. w
William_B Posts: 5225 Rating: (1195)
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This contribution was helpful to 3 thankful Users Prats Juan.Mechatronic GrasserF

5/28/2014 1:50 PM	Rate (0)
Akhgari Posts: 4 Rating: (0)	Thanks for reply. I don't work with micro win pid control. but I know how pid work. My hardware is (1CPU224)+(24ch Analog output)+(12ch analog output)+(14ch thermocouple). I use a pt100 sensor to sense temperature of cooling water. when temperature of water rise up, then fans start to cooling water. My question is " How to control several analog output with 1 loop?"
Akhgari Posts: 4 Rating: (0)
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5/29/2014 8:16 AM	Rate (0)
William_B Posts: 5225 Rating: (1195)	Akhgari Thanks for reply. I don't work with micro win pid control. but I know how pid work. My hardware is (1CPU224)+(24ch Analog output)+(12ch analog output)+(14ch thermocouple). I use a pt100 sensor to sense temperature of cooling water. when temperature of water rise up, then fans start to cooling water. My question is " How to control several analog output with 1 loop?" Dear Akhgari, The advise I give here you have to evaluate carefully as I have never had the opportunity to build cooling towers yet. The assumptions are: there is one body of water, one temperature sensor and the airflow is in one general direction. To answer your base question (quoted above) There is nothing that says the output of the PID must be connected to an analog input. An internal variable can record the PID output. With some rule based logic you can decide which fan should be switched on at which speed. It is better to have a fan run more quickly than having several run very slow. [DESIGN IDEA 1] Split the fans in groups. If the one group are at speed, start the new group. [DESIGN IDEA 2] Have one fan group always be ON.. regulate other fans together with one speed setting. [DESIGN IDEA 3] Have one fan's analog out go into another fan's input to create a master-slave configuration. Control the master fan's speed. The other fans react to a ratio as set on the inverter. [DESIGN IDEA 4] If the temperature is not critical.. use a rule based ON/OFF concept. Each fan group can have 3 or so setpoints selected by digital I/O. Please just keep in mind.. the user set a temperature setpoint. The question: what position in the process should the setpoint be representing? Is the setpoint in the cooling source or is it the process it is supplying (example: blow moulding)? The piping distance from source to process is going to have an influence. The actual setpoint to the PID might need to be offset by a measurement or a rule based system. Keep in mind season and day/night. Helpful / not helpful? Please give the forum feedback with your thoughts. Greetings. w
William_B Posts: 5225 Rating: (1195)
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6/2/2014 2:34 AM	Rate (0)
rg-link Posts: 19 Rating: (0)	Akhgari Thanks for reply. I don't work with micro win pid control. but I know how pid work. My hardware is (1CPU224)+(24ch Analog output)+(12ch analog output)+(14ch thermocouple). I use a pt100 sensor to sense temperature of cooling water. when temperature of water rise up, then fans start to cooling water. My question is " How to control several analog output with 1 loop?" Hi, "1*4ch thermocouple" module for S7-200 and PT100 sensor? Maybe you mean 4xRTD module (6ES7 231-7PC22-0XA0), because the difference between a thermocouple and a RTD is huge...
rg-link Posts: 19 Rating: (0)
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This contribution was helpful to 1 thankful Users William_B

6/3/2014 9:30 AM	Rate (0)
Akhgari Posts: 4 Rating: (0)	thanks all. I changed module "4chthermocouple" with "2ch RTD". I change program with 1 temprature sensor with 1 fan.I want to constant water temperature about 27'C. I read temperature correctly. when temperature greater than set point then fan should run from 0 to 50 Hz. make PID with PID wizard but that's work wrong. when temperature less than set point pid output goes up and when temperature higher than set point, pid output goes on zero. when I try to test "auto tune" micro-win say can not auto tune.
Akhgari Posts: 4 Rating: (0)
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6/3/2014 9:45 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello, To "invert" the PID you can set the Gain to -1 For auto tuning the PID you best add manual control. Bring the output of the PID manualy close to the desired value, then switch to Auto and start the Autotune. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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6/3/2014 11:41 AM	Rate (0)
Prats Posts: 272 Rating: (4)	Dear Akhgari, If you are using Siemens Inverters you can communicate on USS and transfer setpoint etc too.
Prats Posts: 272 Rating: (4)
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