P.I.D is more of a P.I.T.A - Help with auto tune anyone? - Home Brew Forums
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Old 12-27-2012, 09:01 PM   #1
JonClayton
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Dec 2009
Anderson, South Carolina
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I have recently set up a TET-612 PID controller attached to a Honeywell VR8300a gas valve to control the mash temp on my brew stand. I have gone through the PID setup to the best of my ability (granted, that might not be much ability ) and all is well except for 2 issues.

1) Autotune has to be enabled on the PID for the system to work. Otherwise the valve will click but never open and ignite. This is really more of an observation than an issue but....

2) The real issue.. autotune stops running every 15 mins or so. It's impossible to walk away during the mash as autotune will randomly stop working and will need to be restarted. This also happens on a friends sabco brewmagic system so I am hoping its a setup issue.

Is there anything I can do to make autotune constant so that I don't have to continuously monitor it? I admit that I don't fully understand what autotune does, but as long as I can get it to stay on that is all that I care about.

Thanks for any input you can give.



 
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Old 12-27-2012, 11:01 PM   #2
tophmck
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Oct 2009
Madison, WI
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I don't have any experience with this controller, but it sounds like you're using it in PID mode. Since you're using a gas valve, it should be in relay output mode. The manual is pretty cryptic, but I think you want outy=0.



 
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Old 12-27-2012, 11:14 PM   #3
BetterSense
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Jul 2011
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Actual PID is in most situations not even appropriate for brewing purposes. Simple thermostatic control is what you want.

Auto-tuning is not something that you use normally. It's a routine that you can run, and the PID controller software will 'learn' your system so that it can optimize overshoot etc.

 
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Old 12-28-2012, 02:32 AM   #4
JonClayton
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Dec 2009
Anderson, South Carolina
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Thanks everyone. I will experiment with changing the Outy setting tomorrow. I am pretty sure I left it as default value 2. BetterSense, thanks for clarifying that for me. I thought from my understanding that autotune was only so that it could learn the system but then it confused me that it would only control the valve with AT turned on. Hopefully the settings change clears things up.

If I can get this going and receive my new false bottom from Jaybird I think i'll be in business.

 
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Old 12-28-2012, 04:04 PM   #5
JonClayton
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Dec 2009
Anderson, South Carolina
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No dice setting outy to 0. When set to 0 the gas valve does not open (or even click) to light the burner. Any other thoughts?

Thanks!

 
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Old 12-28-2012, 05:55 PM   #6
tophmck
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Madison, WI
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Which terminals do you have the gas valve hooked up to? And what are your settings for AH1 and AL1?

 
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Old 12-29-2012, 05:00 PM   #7
JonClayton
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Top, good question. A friend wired up the controller for me. I will check it out when I am home this evening and report back.

 
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Old 12-29-2012, 06:40 PM   #8
tophmck
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Quote:
Originally Posted by JonClayton View Post
Top, good question. A friend wired up the controller for me. I will check it out when I am home this evening and report back.
OK. From the behavior you describe above, my guess is that the gas valve is currently hooked up as if it were an SSR (terminals 6 and 7). But the manual says that for outy=0 mode, "Relay J1 and J2 as Alarm outputs; SSR Disabled, normally used for upper/lower limits alarm trigger control". In other words, you want to hook up the gas valve to J1 (terminals 4 and 5 see the attached terminal assignments below).

Also, it sounds like you might be trying to set your desired temperature using SV. But you're using the J1 relay to fire your burner (effectively the burner is a low temp alarm), so you need to use AL1 and AH1 to set the desired temperature. Note that AH1 is the temperature you want the burner to fire at and AL1 is the temperature at which it should turn off. (See the attached Figure 5 below.) Note that AL1 must be higher than AH1.

So, just as an example, if you want to maintain a mash temp of 152, you might try setting AH1 to 151 and AL1 to 153.

Good luck!
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Old 12-29-2012, 07:02 PM   #9
whoaru99
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Oct 2012
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Quote:
Originally Posted by BetterSense View Post
Actual PID is in most situations not even appropriate for brewing purposes. Simple thermostatic control is what you want.

Auto-tuning is not something that you use normally. It's a routine that you can run, and the PID controller software will 'learn' your system so that it can optimize overshoot etc.
Yeah, and maybe it's your point but I'm thinking auto tune doesn't work for simple on/off control?
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Old 12-30-2012, 04:18 AM   #10
crane
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Sep 2011
San Diego, CA
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Quote:
Originally Posted by whoaru99

Yeah, and maybe it's your point but I'm thinking auto tune doesn't work for simple on/off control?
Auto tune is used to calculate the gain coefficients for the PID control algorithm, so you are correct it doesn't work for simple on/off control.



 
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