Process Control Schenanigans
Daimonan
Posts: 1
Hello electronics gurus and community!
I'm a marine biologist working on a number of projects, most of which involve (as science tends to) holding one variable constant while changing another. Because I also have a firm background in computer science, I've been asked to look into rigging up a relatively cheap, homemade process control feedback system for water parameters such as salinity, temperature, pH and chlorine.
I've been reading a bit online, but getting into the area of micro-controllers, sensors and process control is pretty overwhelming. So I'm turning to you guys!
Where do I start? I've got most of the summer to work on this project, so I've got the time to learn. From the basic reading I've done, what I want to do is inexpensively build a PID Controller that reads from an analogue sensor (such as salinity as measured by conductivity), decides on the magnitude of the manipulation, and then activates a stepper motor (or maybe a simple on/off valve) which controls the input of fresh water into a tank (which in turn dilutes the sea water).
A system like this would be used in experiments in which water enters from the ocean into a series of tanks, all of which need to be maintained at a different salinity. The PID controller would be responsible for adding the appropriate amount of freshwater to keep the salinity in check.
I'd appreciate any resources you can point me to, and any help or advice that you can give. I have a lot of experience with programming (BASIC, ARM, C, etc), but not much with circuit and hardware design. Everything helps!
Thanks.
I'm a marine biologist working on a number of projects, most of which involve (as science tends to) holding one variable constant while changing another. Because I also have a firm background in computer science, I've been asked to look into rigging up a relatively cheap, homemade process control feedback system for water parameters such as salinity, temperature, pH and chlorine.
I've been reading a bit online, but getting into the area of micro-controllers, sensors and process control is pretty overwhelming. So I'm turning to you guys!
Where do I start? I've got most of the summer to work on this project, so I've got the time to learn. From the basic reading I've done, what I want to do is inexpensively build a PID Controller that reads from an analogue sensor (such as salinity as measured by conductivity), decides on the magnitude of the manipulation, and then activates a stepper motor (or maybe a simple on/off valve) which controls the input of fresh water into a tank (which in turn dilutes the sea water).
A system like this would be used in experiments in which water enters from the ocean into a series of tanks, all of which need to be maintained at a different salinity. The PID controller would be responsible for adding the appropriate amount of freshwater to keep the salinity in check.
I'd appreciate any resources you can point me to, and any help or advice that you can give. I have a lot of experience with programming (BASIC, ARM, C, etc), but not much with circuit and hardware design. Everything helps!
Thanks.
Comments
The Stamps will be able to do this without too much trouble.
Depending on the size of the tanks and the response time of the system , you may not have to worry too much about PID control. Fairly simple on-off control can be quite effective.
I've had Stamps running municipal sewage treatment facilities for 10 years or more; monitoring dissolved oxygen then loading and unloading aeration equipment and logging data as required.
Just ask away in the Forums or send PM's to likely suspects and I'm sure you'll get lots of help.
Where to start? Do a bit of a flow chart of what the control strategy will look like. Then do a layout of what inputs and outputs you need.
Cheers,
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Tom Sisk
http://www.siskconsult.com
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Make LED's blink, have it sense a switch being pressed, control a motor, make some sounds, etc. Follow the projects in the book which comes with this.
This is all quite easy for someone with your background, however microcontrollers are quite a different animal from what you might have been exposed to in computer science (if·programming on mainframes and P.C's?).
And they are different in that you are closer to the hardware. You set up your own LED's or whatever, then write the software to get them to blink or turn on/off.
Quite fun actually!
Then beyond that is the Propeller which I would advise getting if the Stamp will not suit your needs. The Stamp will only do one thing at a time whereas the Propeller has 8 computers in one chip. You can have one computer doing one thing 24/7 and others doing something else. For example you should quickly see that if the stamp is busy doing something, it can't be checking to see if you are pressing a button!
But I would advise starting with the stamp. Take baby steps first and get a good foundation in the basics. You will quickly see how such a microcontroller can be interfaced to various sensors and so forth.
The Basic Stamp is sold at Radio Shack or online here...
http://www.parallax.com/Store/Microcontrollers/BASICStampProgrammingKits/tabid/136/CategoryID/11/List/0/SortField/0/Level/a/ProductID/327/Default.aspx
For the Propeller something similar is the Propeller Education Kit...
http://www.parallax.com/tabid/144/List/0/CategoryID/20/Level/a/SortField/0/Default.aspx
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