What to implement for gaining experience in control loops?

[atferrari]

I intend to gain hands-on experience in control loops (of the PID type). At this stage, op amps to be used.

I am looking for suggestions (the easiest / simplest / cheapest / quickest) on two concrete points:

1) a "plant" that I could implement on my bench.

2) way of tracking ( eventually recording) set point - system output - error - time. If things go not too fast, I guess I could do it manually but not really sure.

After reading a lot, starting with Bob Pease, I concluded that something related to temperature control or motor speed are the best candidates. Have read about a pendulum but sounds complex to start with so I discarded it already.

Suggestions appreciated.

 

[Nigel Goodwin]

For an 'easy' option pick the temperature one - dead easy to monitor, and there's no moving or mechanical parts

 

[Flyback]

control loops using opamp....use my linear regulator simulation in ltspice.

secret is that the opamp with neg feedback always acts to equalise the voltages on its inputs.
Also, the first 50 pages of the book by owen bishop on electronics control is good.

The sim attached

“Understand Electronic Control Systems”
by Owen Bishop
Newnes
…First two chapters, ‘introducing control systems’ and ‘control strategies’ are an excellent description of the general workings of feedback loops…this is very useful for getting a feel for SMPS feedback loops. This is at most half an hour’s reading and well worth it.

 

[dr pepper]

I'm with Nige, temp, maybe a solder iron.
The thing with temps is that it changes slowly giving you time to see whats going on, a motorised whatever would be trickyer to tune without knowledge.
Try implemeting just P and I, you see this a lot in practice.
If your thinking smps steer away from voltage mode if you can and stick to current control, unless your a mathematician.

 

[atferrari]

I'm with Nige, temp, maybe a solder iron.
The thing with temps is that it changes slowly giving you time to see whats going on, a motorised whatever would be trickyer to tune without knowledge.

Yes, as suggested, I decided to go with temperature control. Even if it sounds ridiculous, slow enough to record by hand in the very first tries.

Still wondering the simplest way to bring data into Excel with some tipe of "data logger" (other than by hand!). Yes, I will end with one of my PICs again...

 

[dr pepper]

Dallas 18b20 temp sensor, 1 wire interface to pic, then get the pic to shout the readings through rs232 to excel, or to a buffer file first using tty software or whatever.

 

[atferrari]

Dallas 18b20 temp sensor, 1 wire interface to pic, then get the pic to shout the readings through rs232 to excel, or to a buffer file first using tty software or whatever.

As soon as I have the first part running (with me as the ATE) I will move to that.

 

[atferrari]

control loops using opamp....use my linear regulator simulation in ltspice.

secret is that the opamp with neg feedback always acts to equalise the voltages on its inputs.
Also, the first 50 pages of the book by owen bishop on electronics control is good.

The sim attached

“Understand Electronic Control Systems”
by Owen Bishop
Newnes
…First two chapters, ‘introducing control systems’ and ‘control strategies’ are an excellent description of the general workings of feedback loops…this is very useful for getting a feel for SMPS feedback loops. This is at most half an hour’s reading and well worth it.

Gracias for posting that .asc file FB.

The book, not easy to get here (this is a ridiculous country!!). Anyway I will keep an eye on any chance to get it.

 

[Flyback]

thanks, that opampo sim gives you a total easy control loop to understand...thats what control loops are in many cases.....you just shove a reference on one input which corresponds to your regulated-value being at the demand level, and then the opamp does the rest and drives its output to bring the other input to the same voltage level, so that the voltages at the inputs to the opamp are the same.

obviously you need to set the feedback compensation components correctly..