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PID controll setup...

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PID controll setup...

Postby Zombie » Wed Dec 25, 2013 2:21 pm

Hi, I am interested in trying PID controllers on an experimental Pot still design. Th thread is under "Show us your rig".
viewtopic.php?f=43&t=3435
My idea is mounting the PIDs Temp probe in the vapor output path as it enters the condenser. I understand why the controller will not work measuring wash temp (212^ ceiling) but I do not understand why some say it will not work in measuring vapor temp. Especially since the probe is so far removed from the actual wash temp.
In theory couldn't you set the target temp to say 300^, and adjust as needed to control boil? (non manual pid)
Following the same concept I know (manual mode) controllers be used by adjusting duty cycle.

i assume a well insulated probe could maintain set (ie: 175^ vapor temp) but have been told it cannot done with no explanation as to why. This is really more for something to than any practical reason, soo... any thoughts? :confusion-shrug:
A buddy, and his wife say to me... Hey Zomb, Why don't you make us some Vodka? ............ That was October 2013. Last night (March 2014) I told them I am still designing the still I think I need.
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Re: PID controll setup...

Postby wv_cooker » Wed Dec 25, 2013 4:14 pm

You have several things to think of here and first let me say I have no understanding of the type Still you are experimenting with.

1. First is boiler temp we all know that as each fraction is removed from the wash that the remaining liquid temperature rises until there is nothing left but water at that point the temp is 212 degrees and stays there. I see guy's use pid's in manual mode to try and control this. To me, and opinions vary, it is a waste of money and equipment to try to control the heating element with a pid a simple ssr or similar with a Potentiometer is just as good and in my opinion better.

2. Column temp would be the second thing and I do know one fellow that is doing this with PID, however he is reading the column temp under the dephlegmater on a plated column and using the PID to control coolant water. I can see this working however a better method to me would be to read the temp of the coolant and it would have a better and more accurate control over keeping the temp down with the least amount of flow.

3. As we all know the wash temp takes care of itself in the boiler and by the same token the fractions take care of them selves in the column. This only leaves one thing that can be controlled accurately in my opinion and that is coolant. How to do this, control the deph coolant by coolant temp to accurately set the reflux rate. And secondly control the Product condenser coolant to keep the product as cool as possible. In my opinion this would make a better product with less smearing than any other method. Just my thoughts hope it helps.
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Re: PID controll setup...

Postby Zombie » Wed Dec 25, 2013 6:28 pm

Thank you for taking the time to explain this. i have never used a thermometer in a pot still so I had no idea of the dynamic nature of the vapor temp inside the collector. I was under the impression the Vapor temp held steady. As far as manual controlling of a PID that sort of negates the design of the unit making it pointless to use one. I do have two different types/brands (PIDs) that I have purchased but I do have other uses for them (back up plan) so nothing lost there.
I have been using PWM/SSR combos for a few years, and will most likely build another for this small prototype still I am building. The idea of that still is to equal the purity of a reflux design using less space.
Your points on water flow control are easy to understand but that is wayyyy down the road for me. I'm used to running barley whiskey, and cane juice/molasses rum from pot stills. I just recently am taking an interest in vodka/gin. My gaol is building a single run still with good results that doesn't need a 12' tall tower or two runs. The prototype still may do this and thanks to your input I think I will stick with the controllers I know.
I appreciate the reply, and info. It does pay to seek out advice. Happy New year to you all!
A buddy, and his wife say to me... Hey Zomb, Why don't you make us some Vodka? ............ That was October 2013. Last night (March 2014) I told them I am still designing the still I think I need.
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Re: PID controll setup...

Postby Zombie » Sun Dec 29, 2013 7:42 am

Looks like my "wayyy down the road" has come sooner than expected. With the help of the answers posted to my questions I will be integrating 3 or more PIDs into a full scale build. I am going ahead with a horizontal 6" x 6' recirculating column using internal cooling coils. PIDs will be used independently to control the vapor reflux inside the column via 110 volt coolant circulation pumps.

I am very grateful for the reply's to my questions. The whole idea of this build most likely would have been a failure if not for the help I have received here. I tried posting these concepts on a "sister" forum, and was greeted with a wall of flour paste, and quick dismissals. None of that took place here.

WV Cooker, and Myles... Thank you! Also a true thank you to all the others here that didn't throw Paste. You all exemplify what forums are intended for. Exchanging knowledge, and ideas.

Happy New Year all... Thank you! Z
A buddy, and his wife say to me... Hey Zomb, Why don't you make us some Vodka? ............ That was October 2013. Last night (March 2014) I told them I am still designing the still I think I need.
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Re: PID controll setup...

Postby welska » Tue Jan 07, 2014 4:10 am

wv_cooker wrote:You have several things to think of here and first let me say I have no understanding of the type Still you are experimenting with.


3. As we all know the wash temp takes care of itself in the boiler and by the same token the fractions take care of them selves in the column. This only leaves one thing that can be controlled accurately in my opinion and that is coolant. How to do this, control the deph coolant by coolant temp to accurately set the reflux rate. And secondly control the Product condenser coolant to keep the product as cool as possible. In my opinion this would make a better product with less smearing than any other method. Just my thoughts hope it helps.




Do you think the fellow that is controlling "deph" temp would be willing to share some of the details of his control system?
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