Temperature Control - S7-1200 Tia Portal

Hi,

I'm developing a program to control the outlet temperature of a shower. For this I'm using two water inlets, a Hot (45ºC +/- 6ºC) and a Cold (22ºC +/-4ºC), and a 3-way ball vale to control the mixture (Siemens - VBI61.15-1.6).

This valve is controlled by an actuator (Siemens - GQD161.9A) which receives a 0-10V signal to control the opening position and send an 0-10V signal to signal the position in which it is at the precise moment.

However, I do not know how to control this temperature. Probably I will need a PID, won't I? Since I'm very new to programming and especially in Siemens, I do not know what I should do. Would it be possible for someone to help me and give me some suggestions or literature examples where I can read and learn about it so I be able to do the programming?

Thanks in advance for all the help.

Hi, 

For a PID example PID Control with PID_Compact (S7-1200).

For a PID_3Step see SIMATIC S7 S7-1200 Programmable controller Under chapter: "9.2.4 PID_3Step instruction"

I hope I could help!

MicroMan

Hi, 

For a PID example PID Control with PID_Compact (S7-1200).

For a PID_3Step see SIMATIC S7 S7-1200 Programmable controller Under chapter: "9.2.4 PID_3Step instruction"

I hope I could help!

Hi,

Thank you very much for the suggestions. I will read it and try to do what I need.

Sorry for the question, but this two block are suitable for my situation? 

Hi, 

If you open the PID Control with PID_Compact (S7-1200) under chapter "4.1 Hardware adaptation", you can find out if the example adoptable for your case.

I hope I could help!

MicroMan

Hi, 

If you open the PID Control with PID_Compact (S7-1200) under chapter "4.1 Hardware adaptation", you can find out if the example adoptable for your case.

I hope I could help!

 I apologize if the question was a bit silly but I did it because I did not understood correctly the example. And in fact I'm still in doubt because the example (although it helped me to realize how PID_Compact works) is directed to the control of a fan/motor and I have some fear that is not suitable for my case, which is to mix water accordingly to the movement of a ball valve.

From what I saw of other examples that you suggested the PID_3Step should be more suitable for what I intend to do, right?

Thanks again for all the help

Hi, 

See SIMATIC S7 S7-1200 Programmable controller on page 428 where it says:

"The PID_3Step instruction configures a PID controller with self-tuning capabilities that has been optimized for motor-controlled valves and actuators." 

As you said you use 0-10V Analog Output.  See SIMATIC S7 S7-1200 Programmable controller on page 431 where it says:

"If Config.OutputPerOn = TRUE, the parameter Output_PER is used."

I hope I could help!

MicroMan

Hi, 

See SIMATIC S7 S7-1200 Programmable controller on page 428 where it says:

"The PID_3Step instruction configures a PID controller with self-tuning capabilities that has been optimized for motor-controlled valves and actuators." 

As you said you use 0-10V Analog Output.  See SIMATIC S7 S7-1200 Programmable controller on page 431 where it says:

"If Config.OutputPerOn = TRUE, the parameter Output_PER is used."

I hope I could help!

Hi,

Thanks a lot for the suggestions and I sort of understand now what you meant, and I think that probably the PID_3Step should bettert suited for my application than the PID_Compact.

However, during my search on the forum topics I found something that scared me. One of the topics (Topic) I found a review (2nd) saying the PID_3Step would normally be used to control for 2 states (only open - closed command). This must have been a misunderstand from my behalf, must not? This block is used to command more positions, isn't it?

Thanks again for all the help that you have been giving me

Hi,

The type of the block output usage seems optional.

See the table in SIMATIC S7 S7-1200 Programmable controller manual on the page 430/431.

It says about "Output_UP": "Digital output value for opening the valve. (Default value: FALSE)
If Config.OutputPerOn = FALSE, the parameter Output_UP is used."

It says about: "Output_DN":"Digital output value for closing the valve. (Default value: FALSE)
If Config.OutputPerOn = FALSE, the parameter Output_DN is used."

It says about "Output_PER":"Analog output value.
If Config.OutputPerOn = TRUE, the parameter Output_PER is used."

If you have a look at the "Map" on page 433. On the "MAP" it seems like that the "Config.OutputPerOn" is the selector.

I hope I could help!

Note: Motorized Valve. Look at for example Actuators SAX.., SAL.. for valves Basic Documentation .Search for "Positioning signal" keyword.

Hi MicroMan,

Now I get it, the topic I read should be for a specific case in which only those positions were needed. And I realized now that in my case I should use the Output_Per to control my actuator. 

I've been watching the valve's example you sent and I learn a little bit more about the position signal. In my case the actuator I'm using is the GQD161.9A and the valve is VBI15-1.6.

Howeverm when I was starting to setup the PID_3Step a great number of doubts emerged (i'll number them). Would it be possible to help me?

1- once I've the Input_per enable, I'm in doubt whether the values I put are right. In the scaled high process value I put the maximum measure temperatura of the thermocouple according to the datasheet, namely +250ºC , and in the low -75ºC. There Are the correct values to put or I'm not understanding it?

2 ~in the process value limits I put the temperature values to be expected for the hot and cold water inlets, namely 10ºC (cold inlet temperature) for the process value low limit and 45ºC (hot inlet temperature) for the process value high limit. Am I doing it right?

3 - in the actuator settings part, more specifically in the output value limits, I did not understand what I should put in the high and low limit value output. Why the percentage? What does this mean? I've read the help about it but I did not understand what it meant.

4 - still on the actuator settngs, in the scalling feedback part, I do not know what to put in the high and low endstops. I read the help and everything I found but I do not know what to put in here and also do not know what is for.

Thank you for the all the help and sorry if most of the questions are silly

Hi,

These settings are application specific. I try to help you to find you the right manual entries.

Maybe have a look at the SIMATIC S7-1200 Easy Book under "A.8 RTD and Thermocouple modules" and "A.8.5 Thermocouple type".

About limits, maybe have a look at the SIMATIC S7 S7-1200 Programmable controller.

I hope I could help a bit!