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How to make a system: PID control - PWM - Solenoid valve (Simatic S7-300)

Created by: T2007 at: 1/31/2007 9:08 PM (7 Replies)

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1/31/2007 9:08 PM	Rate (0)
T2007 Posts: 7 Rating: (1)	Dear all, To control the flow througha solenoid valve (with a feed back signal) I have written a control program in Step7, used timers tosettime on and offfor opening andclosing the valve. Now I have to develop the PID algorithm anduse Pulse Width Modulation (PWM) to control this solenoid valve. (Feed back signal ->PID -> PWM -> the solenoid valve-> regualte time on/ off of the solenoid valve -> control flow of the solenoid valve). I have read some example about temperature PID control but I still confused how to begin with PID? how to use some availlable PID block like: FB41(TCONT_C); FB58(TCONT_CP) as well as how to organize a program with PID control step by step? How can I use PID in the mode of the Pulse Control or how to connect it with a available PWM intergrated in the Step 7? I'm just a begginer in PLC and in programming, would you be so kind to helpme and send me your advice to solve my problem! Thank you in advance! Your sincerely, T2007. My email: bangkokhanoi2007@yahoo.com
T2007 Posts: 7 Rating: (1)
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2/1/2007 11:33 AM	Rate (0)
Cicero Gold Member Joined: 10/10/2005 Last visit: 10/18/2024 Posts: 1921 Rating: (136)	Hello, regarding to your inquiry please find the FAQs (links) which do you will find in the internet by the custome support. http://support.automation.siemens.com/WW/view/de/18459342 http://support.automation.siemens.com/WW/view/de/16532187 http://support.automation.siemens.com/WW/view/de/2361324 With best regards Cicero

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2/2/2007 11:18 AM	Rate (0)
T2007 Posts: 7 Rating: (1)	Dear Mr. Cicero, Thank you very much for your message! When I write my on/off control program in Step 7 in the first step I make an OB1and then some fucntions: FC1, FC2.... and call these FC-sin OB1. To write the PID control program, in theory like your websites, I understand that, I have to organize a program with OB35, use somePID block likes:FB41; FB43...but I stillconfuse about how to do it? thereare may be somesteps differ from the simple program I have written. Would you be so kind to instruct me step by step in basichow to write a simple PID program by using the available blocks in the Step 7! Once again, thank you very much! Your sincerely, T2007.
T2007 Posts: 7 Rating: (1)
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2/4/2007 1:52 PM	Rate (1)
Late Platinum Member Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Hi, When you look in the examples in STEP7 choose "File" --> "Open..." --> TAB "Sample Projects" and open the project "zEn01_13_STEP7__PID-Temp", that is a example where everything is shown what you want.
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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2/10/2007 6:15 PM	Rate (0)
T2007 Posts: 7 Rating: (1)	Dear Mr.Late, Thank you so much for instructions! I have spent several days for studying these examples and now I have aquestion thatI do not understand yet. -There are only the gain (GAIN - Real), the reset time (TI - Time) and the derivative time (TD- Time) in the inputs of FB41. How can Isetand display in the HMI (WinCC) the parameters Kp, Ki, Kd (REAL) that connect to FB41? How can I convert value between real and time formats? Would you be so kind to give me your suggestion! Best regards, T2007.
T2007 Posts: 7 Rating: (1)
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2/13/2007 11:21 AM	Rate (0)
Pandiani Bronze Member Joined: 10/31/2005 Last visit: 9/4/2024 Posts: 366 Rating: (31)	I'm not really sure what do you mean T2007? Do you want to enter values for Kp, Ki and Kd in real format from operator through HMI? You must be aware of PID form that is used in FB41. I belive it is in form: Kp*(1/Tis+sTd+1) in Laplace domain. So if you use Kp+Ki/s+sKd form in your calculations, you need to recalculate PID parameters, store them in some datablock or marker memory and transfer use that memory variables as inputs to your FB41 block in STEP7. I hope that helps!

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2/13/2007 9:14 PM	Rate (0)
T2007 Posts: 7 Rating: (1)	Dear Mr. Pandiani, Thanks for your message! Yes, you are right, in the first time I'd like toenter values for Kp, Ki and Kd in real format from operator through HMI. After reading the document,I agree with you that theparameters of PIDused in FB41 are Gain; Ti; Td; which, for a simple case,can besetin HMI to regulate PID parameters. Regarding to the PID control, I have a new problem when I try to use the FB43, the PULSEGEN.I have a book: "Standard software for S7-300 and S7-400 PID control" and itshowsthat, FB43 will work in combination with FB41 "CONT_C". But there are an extra requirement about PULSE_CTR (FB50 , DB50 ) and OB100. I'm still confused about how to connect PULSE_CTR+ FB41+FB43 and OB100? Should I write myself the FB PULSE_CTR? I try to find out the FB50 and DB50 in the Step 7 but I can not find them. Please clarify and give me your advice how to usethe FB43 withthe combination! Once again, thank you very much for your help! Best regards, T2007
T2007 Posts: 7 Rating: (1)
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2/14/2007 2:22 PM	Rate (0)
Pandiani Bronze Member Joined: 10/31/2005 Last visit: 9/4/2024 Posts: 366 Rating: (31)	Unfortunately, I don't have any practical experience. I know what I have read in help. I'm sure there are experts here who eill answers these questions.Examples in Help files are made in CFC (at least I think so).I'm very interested to read answers and learn this too.

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