PID and PWM in same controller revisited

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kzimmer0817

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E-Brewers,

From my reading, it appears that a PWM connected to a SSR would be a simple and inexpensive way to control one's heating element manually. I'm thinking that accomplishes the same thing (perhaps not in the same manner) as the knob on the electric stove. This system would be totally manual. If I wanted to progress "gradually" into electric brewing, building/using a PWM might be a good entry point. All it does is electrify what I'm doing manually with my current burner's valve - although I would have much better control using electricity with a PWM than I do with my current propane cooker.

With the PID, I can set the temp I want, and it will power the heating element (thru a SSR) until the set point is reached. My understanding is that the element is fully on during the heating time.

When it's time to boil, it appears that folks shift their PID to manual mode and set it to a certain % of power (exact % found by experimentation). In this manner, it is functioning like a PWM - although I don't know if it accomplishes this by modifying the pulse width, but it shouldn't matter to me.

Someone mentioned that it was somewhat of a pain to set the PID to manual mode - that it took about 30 seconds to do this. If this is so, I was wondering if one might include a PID and a PWM in the same control box. I saw a thread where the idea of having both controls was mentioned, but it appeared that the PID and PWM were being connected in series. The concensus was that this was not a good idea.

My question is considering it from a slightly different angle. I'm suggesting that a DPDT switch be inserted into the circuit between the PID and the SSR where the operator chooses between PID control vs PWM control. The PID and PWM are totally separate.

I'll refer to the schematic for Johnodon's build for purpose of illustration (go to post #6 in the thread):

www.homebrewtalk.com/f170/my-official-e-biab-build-thread-269164/#post3263178

A double-pole A/B selector switch would be placed across the lavender and yellow wires that run from contact # 7 & # 8 to the SSR. I usually think of this kind of switch as a "Y" where power enters the bottom of the Y and one chooses which upper arm to send it out. In this scenario, the "Y" would be turned upside-down such that the 2 contacts from the PID would be connected to one "arm" of the Y and 2 contacts from the PWM could be connected to the other "arm". Two contacts would then go from the "base" of the Y to the SSR. This way, the PID and PWM are not interfering with one another. Of course, I would have to introduce a 9VDC circuit to power the PWM. This PID vs PWM selector switch would be "in addition to" the "Element ON/OFF" switch.

So, with BIAB, during the heating of the strike water, the above-mentioned switch would be set to "PID". During mash, adjustments will be made to the PID. Perhaps, the PID might be used to get just about to boil - perhaps even the alarm go off at 200*F. Then one might flip the switch to "PWM" and control the boil using the potentiometer on the PWM. At the end of the boil, the "Element" switch is turned OFF. With the PID still ON, the temp during cooling can be monitored.

NEVERTHELESS (emphasis), IF it's really quick and easy to get into "Manual Mode" on the PID and adjust the boil this way, then this entire message becomes irrelevant. I won't mind being told so.

Thanks,
Keith
 
E-Brewers,

From my reading, it appears that a PWM connected to a SSR would be a simple and inexpensive way to control one's heating element manually. I'm thinking that accomplishes the same thing (perhaps not in the same manner) as the knob on the electric stove. This system would be totally manual. If I wanted to progress "gradually" into electric brewing, building/using a PWM might be a good entry point. All it does is electrify what I'm doing manually with my current burner's valve - although I would have much better control using electricity with a PWM than I do with my current propane cooker.

With the PID, I can set the temp I want, and it will power the heating element (thru a SSR) until the set point is reached. My understanding is that the element is fully on during the heating time.

PID, PWM, the knob on the stove (know as an Infinite Switch) all do the same thing. They turn the element 100% on or 100% off. PWM and Infinite Switch are a strictly manually controlled means of doing this. A PID is just smarter about turning it on and off so that it can maintain a specific temp.

When it's time to boil, it appears that folks shift their PID to manual mode and set it to a certain % of power (exact % found by experimentation). In this manner, it is functioning like a PWM - although I don't know if it accomplishes this by modifying the pulse width, but it shouldn't matter to me.
Yup. It generates a pulse, you specify an amount of time (2 seconds normally) and then what percentage of that 2 seconds you want to be ON. It's just like a PWM or Infinite Switch now.

Someone mentioned that it was somewhat of a pain to set the PID to manual mode - that it took about 30 seconds to do this.
That person might not have understood how to switch it. The Auber PIDS can be changed to manual through a menu system, or by pressing the handy [A/M] button on the front of it. Using the [A/M] button takes only a second or two.

If this is so, I was wondering if one might include a PID and a PWM in the same control box. I saw a thread where the idea of having both controls was mentioned, but it appeared that the PID and PWM were being connected in series. The concensus was that this was not a good idea.

My question is considering it from a slightly different angle. I'm suggesting that a DPDT switch be inserted into the circuit between the PID and the SSR where the operator chooses between PID control vs PWM control. The PID and PWM are totally separate.
This is exactly how my system is built. I did it simply because I wanted the ability to expand without over-purchasing control pieces. I bought a cheap PID (no manual mode) and built a PWM for like $3.

I currently do not have a dedicated HLT. I have one e-kettle that serves as a HLT and then later acts as my boil kettle. I select the PID or the PWM as the source for the SSR depending on what I am doing.

If I ever expand and add a second e-kettle, my controls are already there, I just need to dedicate the PID and PWM to the two separate kettles and get rid of the selector switch. No new control HW to buy and install.

NEVERTHELESS (emphasis), IF it's really quick and easy to get into "Manual Mode" on the PID and adjust the boil this way, then this entire message becomes irrelevant. I won't mind being told so.
It's quick and easy to flip between manual and auto mode on an Auber PID, so I guess this is irrelevant.

But at least you know that the stove knob is called an Infinite Switch now. :D
 
It's quick and easy to flip between manual and auto mode on an Auber PID, so I guess this is irrelevant.

But at least you know that the stove knob is called an Infinite Switch now. :D

Walker,

Thanks. When something seems to make a lot of sense, but you don't see anyone else in the bunch doing it, there's probably a good reason why. I certainly don't need another switch, knob, plus circuitry if it's not necessary or helpful. So, now it's a matter of:

1. building an e-kettle
2. getting a definitive concept/design for my control box
3. get er done.

Thanks,
Keith
 
I suggest you dont start a bunch of threads on the same subject. Yes they are a bit different i know but there all about your rig. It will be easier for people to follow along and help you if all your stuff is in one place. Then when you finish if you want to start a new one to show it off thatd be great.
 
I suggest you dont start a bunch of threads on the same subject. Yes they are a bit different i know but there all about your rig. It will be easier for people to follow along and help you if all your stuff is in one place. Then when you finish if you want to start a new one to show it off thatd be great.

i'll second that...

The switching between the two is a good idea for BIAB. If you are planning on switching to a more traditional 3 vessel system in the future you can just rewire and use the pid for HLT or MT control as it wont be needed on the kettle anymore
 
I suggest you dont start a bunch of threads on the same subject. Yes they are a bit different i know but there all about your rig. It will be easier for people to follow along and help you if all your stuff is in one place. Then when you finish if you want to start a new one to show it off thatd be great.

Sorry, TJTHEBEST, I did start 2 threads late last night. I omitted one in which I was asking some questions about terminology. I figured that I could ask those questions along the way.

The 2 threads I started was "this" one to revisit the idea of having the PWM and PID in the same controller. I didn't want to muddy up a "build" thread with that. Later, someone else might have a similar question, and the single-topic thread might be easier to find on searching. It appears that my question was answered - just use PID, no need for PWM.:)

The 2nd thread is my "planning" thread where I hope to get my control box planned and receive advice. When I actually start building it - and the kettle, etc. - I'll probably change the title.

Thanks,
Keith
 
i'll second that...
The switching between the two is a good idea for BIAB.

JTSIMS21,

Thanks. My main premise for asking about that was that someone had said that it was a pain to switch the PID to "manual" and dial in the desired % power. I figured that having a toggle to switch control of the element from the PID to the PWM would be simpler. During boil, I only need to adjust the rate of boil - nothing fancy.

Others have said that it's no problem to switch the PID to manual control. That appears to negate any advantage I might gain; therefore, it might not be worth the trouble to include it. Sure, it might be cool to have another switch and knob on the panel.

Thanks for the input,
Keith
 
This is exactly how my system is built. I did it simply because I wanted the ability to expand without over-purchasing control pieces. I bought a cheap PID (no manual mode) and built a PWM for like $3.

<snip>

It's quick and easy to flip between manual and auto mode on an Auber PID, so I guess this is irrelevant.

Walker,

I started at the first page (earliest postings) on the Electric Brewing page and came across your thread from April 2010:

https://www.homebrewtalk.com/f51/my-herms-build-ready-criticism-173077/

It appears that the center portion of your diagram is exactly what I was looking for in my first post of this thread. With a switch, you are able to determine what will control your element: the PID or the PWM.

You mentioned that you had purchased a very inexpensive PID that didn't have a manual mode, so you must use the PWM to control the rate of your boil.

I'm guessing that the newer PIDs have "manual" mode and that it's easy to get into "manual" mode. Therefore, there is not much need for having both.

If you were to do it again, would you include both in your build? I'm assuming that, for 3-vessel brewing (not BIAB), you would use the PID to control your HLT. When it's time to boil, you would switch your control to the PWM and your element to the one in the BK and use the PWM to control the BK element.

I'm thinking that - if it's easy to get to manual mode on the PID - I should K.I.S.S. and omit the PWM and use the PID for both mashing and boiling.

Thanks,
Keith
 
If I had to do it all over again I would not use separate controls. I am quite happy with the way my system works and do not see the need for a dedicated HLT.

I would just buy a PID that supported manual mode and be done with it.

Maybe someday I will add a dedicated HLT, but that would just be because I was bored and wanted something to work on.
 
Please correct me if I'm wrong but would you want to continue controlling temperature while in PWM mode? Or am I missing something here?
 
Please correct me if I'm wrong but would you want to continue controlling temperature while in PWM mode? Or am I missing something here?

No temp control. People use the PWM to control the strength of the boil, and the temp is irrelevant.
 
Now I understand. I was thinking of a dual purpose heat controller, one that could be used for boil and for mashing.
 
That would be the SYL-2352 PID from Auber Instruments. (Or one of their other models.)

OK, I have something similar coming from direct from China but not from a eBay seller. I believe it does not support PWM but I'll know when it gets here. It's a REX-C100 that is supposed to display F & C and have a control output for a SSR.
 
OK, I have something similar coming from direct from China but not from a eBay seller. I believe it does not support PWM but I'll know when it gets here. It's a REX-C100 that is supposed to display F & C and have a control output for a SSR.
The reason that I recommend the Auber Instrument PID is that it has a manual mode where it can control the percent of power delivered to the element. It contains the function of the PWM within the PID. I've not seen other vendors offer a similar unit.
 
I can confirm P J's recommendation of the auber syl- 2352. When I built my system I looked all over the net and the only PID I could find with manual control was Auber's model's.
 
Please correct me if I'm wrong but would you want to continue controlling temperature while in PWM mode? Or am I missing something here?

Tom,

When it's time to boil, you don't need to control the temp of the boil. Boiling wort only gets so hot. You simply want to have a comfortable boil, not a wicked one. Therefore, it's OK to simply manage it manually using a PWM just as if you were turning down the gas on a gas stove.

While heating strike water, maintaining mash temps, raising the temps to a certain point before maintaining again (as in step mash), I'm thinking that it's best to use the PID for control so that it heats, then cuts off until the temp drops a little.

One could do the entire process using a PWM instead of the PID, but you would have to monitor the temps carefully and adjust the knob accordingly. It's essentially the same thing folks do when they're brewing small batches on the electric kitchen stove.

From what I've been reading on the forum in answer to my original question, it seems that the Auber PID is very easily placed into "manual" mode, so that all you have to do is to set it at 75-80% power to maintain a comfortable boil. Therefore, I've decided that it would probably not be necessary for me to try to include it in my controller.

Hope this helps - and, most importantly, that it's correct.
Keith
 
I'm looking for confirmation, too.

A PWM can be used to regulate the strength of the boil in the BK like on a stove or with LP, you have to monitor and adjust to suit. A PID regulates, too, but with a temp probe will use the calculus to get to steady-state bang-on without us having to monitor things.

Right?

B

EDIT: As my mind ponders what I want to do, I figure having only one of my two BK elements adjustable is what I've settled on. The other BK element and the HLT element will be simply manually switched with a 120v/20A DP wall switch.
 
Based on this thread I think a PID controller for boil is over kill. Instead you want to switch on so the temp goes to full boil as fast as possible then moderate the heat with PWM. The PWM controller I designed for my stir plates will already do this with the addition of a few parts.

A PID controller would be better used for maintaining & stepping mash temperature and for maintaining fermentation temperature.
 
I'm looking for confirmation, too.

A PWM can be used to regulate the strength of the boil in the BK like on a stove or with LP, you have monitor and adjust to suit. A PID regulates, too, but with a temp probe will use the calculus to get to steady-state bang-on without us having to monitor things.

Right?

B

EDIT: As my mind ponders what I want to do, I figure having only one of my two BK elements adjustable is what I've settled on. The other BK element and the HLT element will be simply manually switched with a 120v/20A DP wall switch.

the PID is set to manual and no probe is needed in the kettle. the PID on manual will pulse on and off to maintain the boil. the vigor of your boil is the percentage of time you set the PID to ex. setting to 80% the element will be on 80 percent of the time and off 20% off the time.
 
I'm looking for confirmation, too.
A PWM can be used to regulate the strength of the boil in the BK like on a stove or with LP, you have monitor and adjust to suit. A PID regulates, too, but with a temp probe will use the calculus to get to steady-state bang-on without us having to monitor things.
Right?

This is going to look like the blind leading the blind. I think the "steady-state" is sort of a misnomer in this situation. The "steady-state" we're talking about is simply a temperature measurement. No problem below boiling temp. The problem is that the "steady-state" of 212*F in your kettle could be a nice little boil (212*F) or it could be a tumultous boil (also 212*F) depending upon how much "heat" you're applying. When you turn down your boiling pot shortly after you add the spaghetti, the boil slows down somewhat, but the temperature stays the same. You've simply turned down the amount of "energy" you're applying.

My understanding is that the PID + Temp Probe cannot regulate the boil. It goes full-strength to get you to whatever temp you want. In "AUTO" mode, it will get you to 212*F (assuming that's where you've set it), and it will heat at full power to get you there. The problem is that the wort boiling very lightly is 212*F and so is water boiling all over the place.

What I've understood from my reading of the forum is that guys will set their PID to "just about" 212*F or 210*F. Then they switch it to "MANUAL" mode to get it to boil, then they adjust the % Power to maintain a comfortable boil. So, instead of turning a knob on the stove, they're pressing the "up" and "dn" buttons on the PID to get it to that point.

I don't think the PID can "maintain" a certain "strength" of boil in Auto mode because it only senses temperature - unless one can program it to use a certain % Power even when heating up in Auto mode.

During "Manual" mode, the PID still shows the temp (212*). I've heard that it can be helpful to see the temp during the cooling phase - after you're turned the heating element off.

Hope this helps,
Keith
 
Based on this thread I think a PID controller for boil is over kill. Instead you want to switch on so the temp goes to full boil as fast as possible then moderate the heat with PWM. The PWM controller I designed for my stir plates will already do this with the addition of a few parts.

A PID controller would be better used for maintaining & stepping mash temperature and for maintaining fermentation temperature.

Tom, if you already have the PWM, there's no issue. I think the consensus was that operating the PID in Manual Mode essentially did the same thin as turning the knob on the PWM. Instead of simply flipping a switch to switch from PID to PWM, then adjusting a knob, one simply goes thru several "button presses" on the PID to adjust the power.

The overkill question might be applicable to the PID if all you needed to do was to boil water. Someone else might think it was overkill to have a 2nd device inside your controller in order to do what you can already do with your other controller (the PID).

Since I have neither at the moment - and am designing my controller as we speak - I had posted the original question to determine if I should have a PID to control getting up to temp and for mash temp control AND have a PWM to easily control the boil with a toggle between the two. I asked that under the impression that it was a hassle to switch the PID between AUTO and MANUAL. I was informed that it's easy.

Keith

Thanks,
Keith
 
Actually, what I read into the thread is a PID controller is a complete waste of money and wiring because it's going to be full on until you reach boil anyway, then you switch to PWM. So if this is the case the answer would be a full on/off toggle switch that starts in the ON position then when you reach full boil you turn the switch off and use PWM to set your boil rate.

That is unless you already have a PID controller and want to add a "coolness factor" to your rig.
 
The reason that I recommend the Auber Instrument PID is that it has a manual mode where it can control the percent of power delivered to the element. It contains the function of the PWM within the PID. I've not seen other vendors offer a similar unit.

I have that PID. I initially used it for my BK and a Johnson controller for my HLT, and that worked fine. Switching from "temperature" mode (automatic) to manual is simply pressing one button on the front. You can still send 100% power to it if you choose, and I always did until after the hot break and then just lower it to maintain a rolling boil, usually 75% or so on my system.

I changed up my system about a year ago, and now have the PID on the HLT, and a PWM on the BK, and I like it but it's not any 'worse' than having the PID on the BK. It's the same thing, except with a dial instead of the PID, really.
 
OK, I have something similar coming from direct from China but not from a eBay seller. I believe it does not support PWM but I'll know when it gets here. It's a REX-C100 that is supposed to display F & C and have a control output for a SSR.
Hate to say it, but you will probably not get what you think you are getting. Most of the REC-C100's out there are counterfeit. They don't control an SSR and they don't read in *F either.

Maybe you will get one that actually does handle an SSR, but even then, the REX-C100 does not support the manual mode as far as I can tell.

The reason that I recommend the Auber Instrument PID is that it has a manual mode where it can control the percent of power delivered to the element. It contains the function of the PWM within the PID. I've not seen other vendors offer a similar unit.

I've seen other PIDs that do PWM type operation, but they are generally much more expensive controllers. The only 'budget' PID I have seen that does it is the Auber ones (and, according to the docs, the Setsos ones on ebay).
 
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