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PID select switch

 
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pattypat




Joined: 03 Mar 2014
Posts: 10



PostLink    Posted: Thu Mar 06, 2014 4:53 pm    Post subject: PID select switch Reply with quote


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Hey guys.

I'm in the planning stages of my own Kal clone, and SWMBO has agreed to let the project go forward (I literally presented an hour-long PowerPoint presentation for her to ask for it and it worked!).

There is a guy on YouTube (azwillnj) who made a Kal clone control panel (though, frustratingly, didn't give Kal or his website any credit in the video. he actually says "this control panel that I designed and built myself"). There are some differences, but still. Anyway.

He does have an interesting extra feature - a PID select switch.

I know it's not a big deal to only use the MLT PID as a temperature readout, and while mashing just have the HLT PID a couple of degrees higher than your intended mash temperature. But, it would be great I think to have a PID select switch so that when mashing, the MLT PID controls the firing of the HLT element directly. It would also be easy to wire up.

My question is, did any of you guys build this into your system, and do you enjoy the feature? Where did you mount the switch on the control panel? I realize this is an unnecessary feature in terms of mash temp consistency, but I do like the idea of directly controlling the mash temperature in this way. Or is this just a stupid idea and I need to get over having the HLT temp a couple degrees higher than the mash temp? Are there any disadvantages to a PID select switch like this?

Like all of you I'm sure, I've only got one shot at building this thing, so I want to make sure I've thought it all the way through (though to be fair, Kal did all of the thinking for us anyway!). Cheers.
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Mar 06, 2014 7:22 pm    Post subject: Reply with quote

Is the switch used to select which temp probe is connected to the PID? If yes, the big issue with this is that one of the two will not read accurately as you have to calibrate the combination of PID & temp probe by setting an offset in the PID. Depending on how the temp probes are used, you may not care if one isn't accurate.

Welcome to the forum and good luck!

Kal

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pattypat




Joined: 03 Mar 2014
Posts: 10



PostLink    Posted: Thu Mar 06, 2014 7:26 pm    Post subject: Reply with quote

The temp probes would be connected exactly as in your setup - the selector switch would simply control which PID controls the HLT element - so if the MLT PID is selected by this switch and set to 152 and the MLT probe/PID reads 150, it would fire the HLT element. does that make sense? so the switch doesn't change temp probes, just changes which PID controls the HLT element. Thanks for the reply! i'm excited to get started.
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Mar 06, 2014 9:10 pm    Post subject: Reply with quote

I don't see why it wouldn't work, but what benefit do you see from doing this? What issue are you trying to solve or fix?

I guess the question really is: What's different from your brewing process as compared to the one I walk through in the BREW DAY STEP BY STEP article? (The control panel should compliment the brewing process you want to use, so without a detailed step by step brewing process it's hard to know if a specific control panel makes sense).

Kal

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AtlasHopped




Joined: 26 Dec 2012
Posts: 26
Location: Reading, PA


PostLink    Posted: Thu Mar 06, 2014 9:52 pm    Post subject: Reply with quote

kal wrote:
I don't see why it wouldn't work, but what benefit do you see from doing this? What issue are you trying to solve or fix? ....



Kal,

I think I could see some benefit in this. Perhaps my build behaves differently from yours, but I find that hitting and holding a specific mash temperature requires some fussing with the temp on HLT PID since the mash temp doesn't really seem to ever come all the way up to the HLT temp. The temp variation between the HLT and actual Mash temp seems to change a bit depending on the batch size, amount of grain, possibly gravity, the ambient room and equipment temp and who-the-heck knows whatelse. It's not a huge deal, but I find myself cranking up the HLT temp by 5-6 degrees to get the mash temp up where it belongs, then dropping it down, then fiddling with it while it equalizes throughout the first 30 minutes of my mash to hit and hold a specific temp.

Since mash temperature can have such a critical effect, I could see the benefit in just setting the temperature I want on the Mash PID and letting it rock and roll.

Just my 2 cents. Which is worth....about 2 cents. If someone gets back to me in the next hour, I'll drop it to 1 cent but I ain't goin any lower.

- Kyle

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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Mar 06, 2014 9:58 pm    Post subject: Reply with quote

Ah! Ok. I get it now.

On my setup my MLT temp follows my HLT temp. Less than a 1/2 degree F difference.

I'd still run through an entire brew day "virtually" and see if there are any gotchas to doing this - just to be sure - before you start punching holes in the enclosure.

Good luck!

Kal

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Sketchin




Joined: 08 Jan 2013
Posts: 169
Location: Calgary


PostLink    Posted: Thu Mar 06, 2014 11:25 pm    Post subject: Reply with quote

I like the idea, but I see a potential problem with temperature ramp times in the hlt. By the time the output of the mash is at the temp that you want, the hlt temp would probably be quite high. Then by the time the mlt temperature was read again, the hlt would would still be too hot and you would have to wait for it to cool down again. Perhaps this differential could be mitigated by training the pid, but the training would dependant on the type of mash, and how quickly the wort travels through it.

Hope this makes sense to someone other than me... Perhaps someone could do a test and simply connect their mlt probe to the hlt pid and see how well it controls the mash temp?
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AtlasHopped




Joined: 26 Dec 2012
Posts: 26
Location: Reading, PA


PostLink    Posted: Fri Mar 07, 2014 6:40 pm    Post subject: Reply with quote

Sketchin wrote:


Hope this makes sense to someone other than me... Perhaps someone could do a test and simply connect their mlt probe to the hlt pid and see how well it controls the mash temp?


Simple enough to test. For some reason I think this one requires close supervision as it has the possibility of becoming a memorable "fail" if your suspicions are right about the temp ramp and PID response.

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lakeannebrew




Joined: 25 Sep 2015
Posts: 1
Location: Reston, VA


PostLink    Posted: Fri Sep 25, 2015 8:47 pm    Post subject: Reply with quote

AtlasHopped wrote:
Simple enough to test. For some reason I think this one requires close supervision as it has the possibility of becoming a memorable "fail" if your suspicions are right about the temp ramp and PID response.


Did anyone ever test this? I had the same thought, but was concerned about the thermal mass of the HLT might not dissipate heat fast enough and overshoot the target mash temp.
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