PID Controller

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Re: PID Controller

Postby pulsetech » Tue Jun 10, 2014 6:06 pm

Actually most commercial Thermostats have 0 - 10 v output.

Arduino is cool but if your going down that route you could look at PWM to the solenoid ( you would need a high duty cycle solenoid like a Kipp valve)
it may be a little surgey (that's not a word :scared-eek: ).
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Re: PID Controller

Postby badbird » Tue Jun 10, 2014 10:49 pm

Have to agree that current loop PID controlling a modulating flow valve would have to be the best solution but surprisingly enough there now a lot of people around getting great results from the cheaper slow switching solenoid valves. Maybe a lot of it has to do with how well the PID is tuned to the task at hand.
I'm told the auto tune on a lot of the cheap (and not so cheap)controllers leave a lot to be desired and its fairly common now to get specialist consultants in to tune up the control loops in mineral processing/industrial plant situations.
There are some good guides to PID tuning to be Googled up but none of them make easy reading :roll:
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Re: PID Controller

Postby RumFiend » Tue Dec 23, 2014 11:56 pm

pulsetech wrote:I am just a Newbie here but being a HVAC tech for 20 years I have a few ideas that would be better to control flow than just solenoid valves.
If this was my system I would look and modulating flow control valves. These take an analogue 1 - 10 v signal. a 3/4 size valve can control flow ( based on mains pressure) between 0.1 LPH to around 15 LPH. in .01 volt increments. ( 100 increments total). If you use a pressure limiting valve before it you will have very precise control. These will run you anywhere from $120 - $300 depending on quality. I would recommend a course filter inline before the valve also.


does anyone have any idea where to find these flow control valves in australia? I've done a bit of searching and can only managed to find american sites selling these things at outrageous prices once you include shipping. the valves themselves are pretty expensive, especially when you compare them to a standard on/off solenoid valve :-x
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Re: PID Controller

Postby Aidymiles » Sun Feb 01, 2015 1:21 pm

Hey RumFiend,
You may also want to look at CNC motors as they have 3 sets of windings and great control over the how far the spindle turns in the motor and would be perfect for a valve motor.
I have done a few arduino projects and have had this idea for a future project but never actually tried it tho.
Hope it helps
Aidy
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Re: PID Controller

Postby Aidymiles » Sun Feb 01, 2015 1:27 pm

Actually now I think about it, cheaper n easier way would be a temp sensor controlling a voltage regulator hooked up to a pump to regulate the flow of water thru the RC. Don't have to worry about expensive valves then.....
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Re: PID Controller

Postby wiifm » Sun Feb 01, 2015 4:36 pm

Just get the on/off valves. the PIDs don't switch them that quickly at all, especially if you put a flow control valve in place to reduce maximum flow rate.

EDIT: to add further, since I posed a question earlier in the thread.

I was running my PIDs in the wrong mode before. Once I switched to the correct mode, all problems I had were solved even with the solenoid valves.
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Re: PID Controller

Postby Meatheadinc » Sun Feb 01, 2015 5:42 pm

I was sceptical of the solenoid valves and wanted proportional valves but after researching the costs involved I went for the solenoid valves
apart form them clicking quite loudly I have found that they perform perfectly.

wiifm wrote:voltage regulator hooked up to a pump to regulate the flow of water thru the RC. Don't have to worry about expensive valves then.....

Finding a DC pump with adequate flow at a reasonable price may be a problem
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Re: PID Controller

Postby Aidymiles » Sun Feb 01, 2015 7:31 pm

Ebay has cheap mag drive 12v dc pumps up to about 20L/min. The head/distance from the ground messes with its flow rate a bit once you get over a metre above the pump. 2 ways around this is check valves or a 2nd pump. Much cheaper than a $250 pump :handgestures-thumbupleft:
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Re: PID Controller

Postby bluc » Tue Jan 09, 2018 8:19 pm

Very interesting thread. I think there is some variable pwm pumps available for pc water cooling. Maybe there is bigger version that could be used for this :-B :think: here is the pc version http://www.frozenqshop.com/d5-mcp655-pwm-variable-pump/
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