PID & Potentiometer together

[pope]

Is it possible to wire a PID to control a heating element but use a potentiometer to throttle the current below the set point? For example, you would set the PID to 99C based on the head temp. The PID will operate in a 100% on/off cycle of current up to the set point, such that it will just be on until it reaches the set point. Could that 100% on current then be throttled with a potentiometer so that there is effectively a max head temperature beyond which your controller will just shut off? Of course it will not shut off in this theoretical scenario, it will cycle on/off until you override via the power switch, but it could be an added feature.

I've build both a PID/ssr setup and a pot/psr setup, I understand enough about these systems to know that there's no place to wire in two control inputs into one ssr or psr. BUT, I should be able to run the load from the SSR/PID side of the control box into the PSR/pot side, which would then flow on to the element.

I'm building a 1500w 'reaction chamber'/mini still out of a 5-gallon pony keg, so being able to run two configurations would be ideal. I.E. these two modes:

Scenario 1, 'reactor' mode: PID set to set point (65C), POT turned up to 100% (or throttled I suppose, to allow for slow, even heating).
Scenario 2, still mode: PID set to set point (say, 99C in the kettle), POT operated in the fashion of a typical spirit/stripping run.

Even in this second configuration with a temperature sensor in the kettle above the element and a set point of 101C, the still should shut itself off once the temperature sensor was no longer submerged, protecting the element if I had a stroke or something (not that I'm worried about that). You could also track the liquid temp in the parrot and have it shut off at a lower temperature (like 40C) in case your coolant flow was somehow interrupted.

My original idea was to wire a box with a SPDT switch to have one power supply with two control sides, each with its own socket. I would then switch the element to the appropriate socket and fire away. This seems less complicated to operate and maybe adds a little safety, but I figured more brains are better than one.

[NZChris]

I reckon a PID is overkill for a Reactor.
An SCR/whatever, is only needed if the element is a mismatch. On another task, I did experiment with having a PID switching current from an SCR, and that worked well, but it was overkill and I won't bother next time.

For my Reactors, I use cheap on/off controllers set to a 0.3C differential. The PTC elements provide only just enough Watts to do the job, taking several hours to get up to temperature. They are placed underneath the vessels to prevent stratification.

For still safety, I use a latched relay. This will shut off the power to the elements if anything daisy chained into the latching circuit reaches a set point.

[pope]

I agree its overkill but if I can have one control box and vessel setup that can do two things, its a space saver and I think it might be less cost and headache in the long run. I'm not as technically savvy as some of you. Though I generally grasp the concepts at hand with enough reading, I don't have an engineering background.

Auber Instruments has this item that toggles between an SSR and PSR function within one unit: https://www.auberins.com/index.php?main ... cts_id=559

They sent me addtional info on how it works here: https://www.auberins.com/images/Manual/ ... lkv1.1.pdf

I might just go this route for simplicity, though it lacks any kind of safety relay.

[pope]

Actually in the case of the above devices, the DSPR400 has extra relay outputs that could be used in latching mode and looped into the power supply.

[NZChris]

Most of my control gear is multi-purpose and isn't nailed down.

I have several STC-1000s in boxes with both heating and cooling outlets that can be used for whatever duty I need them for at the time. One of them is looking after a Reactor I started yesterday. The same one gets used for looking after ferments and controls an element underneath the can, plus a fan for cooling. Another is connected to refrigerator with a heating element inside and will give me whatever temperature I dial in, which is great for fermenting and cold crashing in any season, another is heating a rum ferment in a broken down fridge at the moment. Unfortunately, I've found STC-1000s to be unreliable and a PITA close to boiling point, so I use a W1412 with a latched relay for the main pot still.

The SCR can be dismounted from the main still if I need to use it elsewhere.

The PID gets used for heating makeup water when I put a ferment together, cheese making, yoghurt and sous vide, so it's box has never been mounted anywhere. I was given another one, but I've never set it up because I don't have a job for it that can't be done as well, or better, by something else.

[pope]

STC-1000's are new to me! I want to do another build because I currently have a pid and a potentiometer but they're both 240v 30a wiring/sockets/etc. The new build will be 120v/15a, an STC-1000 would work well for reactor but not still, and I will need both to use the 1500w/120v element as a still. I also want the separate build so that I can run the reactor and still plug along at any other fermentation/stripping/spirit runs I am working on.

As colder weather is around the bend I may do an STC-1000 build for my immersion heater for the open fermenter. What boxes do you use for your STC-1000's? Anything specific or whatever you find? Or do you get enclosed units?

[NineInchNails]

If you use a PID with potentiometer set to 100% power, it would function very accurately. If I'm not mistaken, once you turn the potentiometer down to let's say 50%, I believe the PID would start to act up and not be very accurate. The reason I say that is because the PID learns the heat input in order to be accurate. Once you fudge the % heat input the PID no longer knows the on/off cycles like it did before.

[pope]

That makes a lot of sense. I know I ran a learning program for my current PID to understand the input and load required to bring my beer brewing strike water up to temperature, so of course if the load was variable it would get 'confused'. I'm going to go with Chris' recommendation to use a latching relay to achieve a safety shut-off, I'll figure out how to use one of the auxiliary relay on the unit I referenced to do that.

Chris I now have a rudimentary understanding of a latching relay - what do you use for your latching relay to measure and trip based on a set point? An STC-100? In my mind the most sensible place would be at the parrot, setting a rising liquid out temp to stop the entire system. I would run the system in boil mode using the head temp as a guide, and have it set to 99C as a shut-off point already. I would think an STC-100 looped into the latching relay using the cooling side with a set point of 40C would achieve that goal and safeguard against coolant flow malfunctions.

[NZChris]

I only use the STC-1000s because they were cheap and convenient for me at the time. Use whatever you can get.

I've started using 12V W1209 controllers for a few jobs, like controlling condensate temperature, partly because they work off grid and I like to do a spirit run in the hills and leave a couple of bottles behind. They will handle 20A 120/240vac, but I wouldn't use them to control large elements because the relay looks a bit small for that job. I get a clear plastic case that can be bought with them. A bit ugly, but I'm not trying to impress visitors.

I get my enclosures from a local electronics store.

I don't like submersibles and only use them for heated stirrers if I get the temperature too far out of whack when putting a wash down or heating milk for cheese making. They can cause stratification, leaving the yeast bed cold. I either heat from below, or heat the incubator they are in. My current ferment is in a broken down fridge I got for free, with a PTC element on the bottom. That said, I've recently tried putting an air pump inside the CO2 cap to agitate the wash with bubbles and that should work with many washes, but I don't know how well it would work with a deep grain bed.

[pope]

I like to do a spirit run in the hills and leave a couple of bottles behind.

This makes me think of my buddy's practice of actually burying bottles in the ground to be dug up later. Carefully, I assume.

I'll find a secondary controller for my latching relay that does the trick, thanks for the advise! Submersibles aren't my first choice but they're cheap. I'm running a wine trash can-type open fermenter with cheesecloth over the top, it's about as unsophisticated as it gets. The best recipes get the precious space of my ss jacketed conical fermenter (when there's no beer in there). I prefer to do 10-15 gallon ferments so carboys are out, they mostly hold low wines now (only when cornies are full because I have broken a few).

Agitating with the CO2 off-gassing is very creative! I haven't had a grain ferment get stuck yet, the room stays above 20C, I pitch warm onto a large cake, and it seems like the yeast keeps itself warm long enough to finish. Still I'd love to have all temp-controlled vessels one day. Like a day when I'm in the black with a legitimate commercial operation.

[LWTCS]

PLC with PID and VFD would allow for what you're looking for. But you'd need to know how to write ladder code or know someone....
Spend a few pennies and incorporate an HMI and you can program the PLC to let you change input values on your HMI via touch screen.

[LWTCS]

Here is an example

[pope]

Damn man way to ruin my night! Now I have a whole new rabbit hole to go down

[NZChris]

Chris I now have a rudimentary understanding of a latching relay - what do you use for your latching relay to measure and trip based on a set point? An STC-100?

I use an XH-W1412 with the probe in a thermowell covered by the wash. That temperature allows me to work out the remaining abv in the wash, or shut down at a desired abv.
There is a spare W1209 probe that reaches the still head that I could use to trip the relay when the still head reaches distilling temperature, but I've never bothered to wire it into the circuit because I'm always around watching it.
I could have something watching the condensate temperature in case there is a problem with cooling water, but I never remember to connect one up. I'll try to remember to hook up a spare STC-1000 latched relay next time. Her Indoors managed to park the truck on the cooling water hose a few years ago

[pope]

Lol ‘her indoors’ that’s new to me.

I’ve always operated by looking at the head/vapor temp and shut down when I’m at 99/~10% in the parrot/ 1:3 low wines:wash but usually by head temp. Fixed my ammeter recently and found that extremely useful for setting flow rate by current.

The controller you have is a pretty impressive device and a steal! My favorite feature is “conveniently fits in your life.”I think I’m going to try to build the latching relay with a probe in the parrot. There’s room for a second programmable relay on the controller I’m eyeing so I could use a mini power relay to connect that to a solenoid valve so that it shuts off the still and the coolant at the same time... but that’s more about fun with cool toys than practical safety measures.

Larry I’m sorry but I think the coding and touch screen will have to wait until the next iteration when I’ve had to learn a couple new skills I’m lacking

[NZChris]

I’ve always operated by looking at the head/vapor temp and shut down when I’m at 99/~10% in the parrot/ 1:3 low wines:wash but usually by head temp. Fixed my ammeter recently and found that extremely useful for setting flow rate by current.

You might do better by removing the thermometers in the head and setting your flow rate using your eyeometers.

Readings from ammeters, thermometers and parrots are useful for future runs when you have records to refer back to, not so much for beginner runs when you should just be collecting data.

Although I've been thinking about building a parrot for thirty years and have collected everything I need to build a couple, I've never found a good enough reason to build one. Being at hobby scale, my nose and taste buds are better guides to cuts than temperatures and parrots etc. and I choose my cuts/blends the hard way every time.

[LWTCS]

I’ve always operated by looking at the head/vapor temp and shut down when I’m at 99/~10% in the parrot/ 1:3 low wines:wash but usually by head temp. Fixed my ammeter recently and found that extremely useful for setting flow rate by current.

You might do better by removing the thermometers in the head and setting your flow rate using your eyeometers.

Readings from ammeters, thermometers and parrots are useful for future runs when you have records to refer back to, not so much for beginner runs when you should just be collecting data.

Although I've been thinking about building a parrot for thirty years and have collected everything I need to build a couple, I've never found a good enough reason to build one. Being at hobby scale, my nose and taste buds are better guides to cuts than temperatures and parrots etc. and I choose my cuts/blends the hard way every time.

100%
Installing a generic input value isn't going to be nearly as useful as first determining one's actual point of view in practice.

[WithOrWithoutU2]

You all are some impressive dudes. I don't understand electronics, but I love reading about this next level type stuff.

[pope]

Agree with you guys completely. I'm pretty deep into this (can't believe I bought my first rig ten years ago), I have spent a long time running qualitatively without connecting senses with data, I'm trying to catch up now and drive consistency/repeatability, keep better notes, etc. I came up with 99C for most things but I am still experimenting with chasing that 'sweet water' deeper in the tails of grain spirits - I hope my rule of thumb/ballpark figures don't lead any noobs astray. I think for a long time the 'moonshine' notion kept me shooting from the hip which definitely helped me get a sense for cuts, smells, and flavors (and coming from a beer brewing background helped). But I'd rather know when I'm making a good ferment recipe and stripping it that I already know my charge abv is the same and that the cut off point I've selected matches my taste from past experience on the same batch.

For spirit runs, the dream is still to cut 'on the fly' which is a sensory decision (though having data never hurts unless you lean on it too hard). But my 'on the fly cut' notes on my jar records has yet to align with what I ultimately blend from jars.

[WithOrWithoutU2]

For spirit runs, the dream is still to cut 'on the fly' which is a sensory decision (though having data never hurts unless you lean on it too hard). But my 'on the fly cut' notes on my jar records has yet to align with what I ultimately blend from jars.

I for one have always believed there is a science to everything. And in terms of mastering a process of creation, that science (data collection) will get you closer to a deterministic process versus probabilistic process. Hats off to you folks who are marrying the "feel" approach with the "data driven" approach.

[NZChris]

For spirit runs, the dream is still to cut 'on the fly' which is a sensory decision (though having data never hurts unless you lean on it too hard). But my 'on the fly cut' notes on my jar records has yet to align with what I ultimately blend from jars.

Same here. My flavor notes from during a run are interesting, but seldom match my final choice of blend, with jars predicted to be included left out and jars predicted to be feints included.
What temperatures and past records do tell me during a spirit run, is when I should be collecting in small jars and when I'm safe to run into demijohns. E.g. My last rum run used three jars for choosing the heads cut and seven for the tails cut, the obvious hearts were in two demijohns. The final choice was both wide and narrow cuts to be aged separately.

[pope]

Definitely on the same page! It’s essential to get close on those hearts cuts and use bigger jars/jugs, I don’t have enough quart jars to spread the entire run out like that. I’m still waiting for the on-the-fly to align, until then I’ll keep getting closer.