Automation - Pid Capabilities

[ant]

Apologies for yet another thread, but I'm looking at some basic automation; literally not much more than plug and play.

(Note: when I say basic, I mean without the level of detailed electronics experience shown by some of our members )

I'd like some advice on the viability of this option pls...

OBJECTIVE
Im wanting to automate my HLT heating and mash process, it seems to me that if I can get this to work, I should be able to get up in time for the sparge, cutting a fair chunk off the brewday.

METHOD
My thoughts on control (Phase 1) involve 3 PID controllers, some relays, 3 heating elements, 2 pumps, on e float switch and one actuated 3 way ball valve (and a partridge in a pear tree).

PID#1 (HLT)
- read PT100 in HLT
- if below temp setpoint, activate heating elements in HLT (2 x 2400W @ 240V; will be running on 110V though)
- once at setpoint temp, activate Pump#1 and pump to MLT (volume to be pumped to be set by float switch in MLT)
- turn off Pump#1 once volume in MLT reached

PID#2 (MLT)
- activated once water in MLT triggers float switch
- read PT100 in MLT (exit valve)
- activate Pump#2 and recirculate through MLT (exit from valve at base, through 3 way valve in NC position and back to top of MLT)
- if at or higher than setpoint temp, do nothing
- if below temp setpoint, actuate 3 way valve to Open position and circulate through coil in HERMS unit and back to top of MLT

PID#3 (HERMS)
- read PT100 in HERMS
- if below temp setpoint, activate heating element in HERMS (1 x 1500W @ 110V)
- if at or higher than setpoint temp, do nothing


Does this sound like a reasonable process?

The sort of questions that spring to my mind:
- What do I need from my PIDs? (looking at these)
- Which ones need to be relay or SSR output?
- What size SSRs would be recommended to handle the elements?
- Do I want 1/32, 1/16 or 1/4 DIN? Does it matter?
- Can a PID turn the pumps on and off?
- Can a PID drive the actuated ball valve?


Yours in confusion (but hoping to soon be nodding head sagely),
Ant

:huh:

 

[Doogiechap]

G'day Ant ,
The process sounds fairly well thought through. Some factors that you may want to consider :-

The stirring of the mash during dough in and possibly to remedy a stuck runoff during the Herms cycle.

Detecting of the stuck runoff from your MLT. Flowmeters are fairly expensive (unless you can track some down from your US salvage contacts in which case Tony and I want some too ).

Whilst I have had little experience with SSR's (lots of dealings with coil based relays), the SSR's look pretty attractive with no opportunity for mechanical failure.

The Specs for the PID's state they can drive either so I think it's up to you and your wallet. You will definately need (and should) use relays (Solid State or Mechanical) to drive all of the gear controlled by the PID's.

The DIN size is probably only relevent if you are replacing another device and want to match the hole in your panel..

SSR capacity is something that someone else will have to answer with more authority. My calculated guess would be to pretty much double the switching capability of the SSR to cope with inductance related surges with the equipment.
Mate good luck with this. If I ever get around to any form of automation this is the path I would be taking too.
Cheers
Doug

 

[Zizzle]

I've never worked with PID controllers, so that probably biases my judgement. You'll probably get better advice out of others.

I like the flexibility of microprocessors and software.

For example, in my setup I can detect a stuck sparge by measuring the conductance across the fluid in the pump and writing an algorithm to work out when the pump isn't full. In fact I have written lots of little checks into the code to make sure everything remains sane, and sound an alarm if things go wrong. I guess first of all the machine has to protect itself (don't run the pump or heating elements dry), then produce the beer.

Are you sure you need a 3-way valve? Why not always pump through your HERMS and let the PID take car of the temp?

Also I have seen some discussion about where to put your temp probe: after or before your RIMS/HERMS unit. After seems to make the most sense to me. You want the wort coming out of it to be at you set temp.

My understanding is that the small cheap PIDs will only do the temp control, not the logic around switching pumps based on float switches, or am I wrong?

I haven't bothered with SSRs in my setup. Too expensive when plain old relays will do the job. Although high current triacs are pretty cheap, so it's reasonably easy to make your own SSR.

 

[kirem]

I have used auberins PID controllers on my setup. I like them and they do a god job.

I have them switch SSRs, http://secure.oatleyelectronics.com//produ...1ab16e874b3ff2e

I don't think a PID controller is really suited to switching on/off devices.

 

[snagler]

The auber instrument you mentioned will easily perform any of those tasks. I have rigged one up in a box and use it to control my brew fridge and HLT, I just have to change two parameter settings to use it on either. Get the solid state relay option. I got a 25amp SSR from auber and it is more than enough for my needs, however auber instruments also sell a 45amp SSR that is combatable to the controller.
Here is a copy of my auber order (in US dollars)

1 x 25A SSR (RS1A23D25) = $15.00
1 x 1/16 DIN PID Temperature Controller (for SSR Output) (SYL-2352) = $44.50

You can get more advanced models for more money from auber but you wont need it. I think mine was the base model and still has plenty of features you will never use.

 

[kook]

Ant, check out http://www.plccenter.com/

Loads of cheap, secondhand automation equipment. I picked up my gear from there (had it shipped to a friends in the states).

 

[ant]

Thanks gents for all the replies, I'm starting to get the hang of this all now (I think :blink: ).

Doogiechap - yep, stuck mash is something I've been wondering how to automate; I was thinking of simple solutions (like 300gm rice hulls!), but if I'm wanting to be completely hands off during the mash, I'd better look at something. Maybe a flowmeter providing a signal to a motor driven mash stirrer? In terms of what TYPE of flowmeter, maybe something like the Flow Transmitters see page 521 of catalog here (McMaster.com is the best online hardware place I'ev ever seen - from silicone hose to valves to s/s fittings...). If you let me know what type of flowmeter you (and TONY!) are looking for, I'll keep an eye out in my salvage hunts.

Zizzle - the above being said, I really like the idea of measuring pump flow instead - removes a layer of redundancy. I don't NEED a 3 way valve, but I picked it up for $40 (s/s, 1/2", actuated ball valve... score!) and it seemed a nice gentle way to heat the wort? I agree with you wrt the temp probe, I'll have one at exit of MLT and one at exit of HERMS. As to the use of PID's to switch pumps, etc, I dunno, but it seems the general consensus is they aren't suited for it (see question below).

Kirem - thanks for feedback on the PID's, good to know they work for someone else! What are your thoughts on what would be better suited to driving pumps, etc? This seems to be the bit where my ideas fall in a screaming heap...

Snagler - again, thanks for the feedback on the PID's and size of SSR. Invaluable to have someone who's done it before.

Kook - that place is a goldmine. I'm going to have to hide my credit card, I can see it.

 

[Yorg]

Hi Ant,
Just some quick thoughts:
Re your float switch in the MLT to switch off the flow from the HLT - Depending on the sensitivity of the float switch, after a little evaporation, the level may drop, swiching back the flow from the HLT and your Mash control PID off. Not sure of worst case scenario, but may be cycling a few times.
Re controlling stuff with PIDs. Key concept here is that the PID is not switching your pump or actuator or anything else. It is switching an SSR, which in turn is switching whatever you have connected to it. This is exactly what they are designed for.
Also, as I once read on one of these forums - with all this automation, do you want to be a brewer or a cleaner?
Cheers,
Yorg

 

[Zizzle]

Also, as I once read on one of these forums - with all this automation, do you want to be a brewer or a cleaner?

Maybe some like staring at water for an hour waiting it to heat up? Some of use don't find that especially entertaining.

Like I've said before, the choice for some, since they don't have a spare 4-5 hours for each brew, is a quick & easy automated brew, or no brew at all.

We can still enjoy the recipe formulation and the results, which are the important bits to me.

Building the system is also fun & challenging. The mechanical repetition of brew day is not.

I guess I've always been taught to work smarter, not harder. To each his own. B)

 

[snagler]

My job as an instrument technician in a power station requires me to get things working automatically with minimal manual human interaction useing all manner of fangdangle technical equipment.

As a direct contrast I designed a near manually operated AG setup because I wanted to feel in control of the process and be able to hone my skills.

Mind you Ive only done one AG brew with my rig. Who knows I might soon get jack of this manual way and go auto - I just hope this doesnt happen because it will probably mean Im loseing interest.

 

[kirem]

Maybe some like staring at water for an hour waiting it to heat up? Some of use don't find that especially entertaining.

Like I've said before, the choice for some, since they don't have a spare 4-5 hours for each brew, is a quick & easy automated brew, or no brew at all.

We can still enjoy the recipe formulation and the results, which are the important bits to me.

Building the system is also fun & challenging. The mechanical repetition of brew day is not.

I guess I've always been taught to work smarter, not harder. To each his own. B)

here here!

 

[Yorg]

here here!

Oh I'll third that :excl:

 

[Nauticaldisasta]

Solid state relays are the way to go for sure.

When running temp controllers in PI or PID mode, the switching frequency of the output device can be fairly high.

SSRs are the only way to go unless you like replacing relays once the contacts have burnt out.

To size a SSR correctly, you really need to consult a current/temp chart- available from the manufacturer. I have seen some pretty spectacular SSR failures due to inadequate heatsinking or thermal dissipation.

Zero Cross SSRs are better to use as they avoid creating too much electrical noise when they switch.

For a couple of hundred dollars, Siemens (as do other manufacturers) make a "programmable relay" called a LOGO! It's a kinda dumbed down PLC. The beauty of these little beasts are that they are fully programmable from the front LCD panel via the buttons on the front. No hard to learn progamming languages, no expensive software to buy, no PC cables needed, although all that is available for them. Depending on the model, they have a couple of analogue inputs, Digital inputs and digital outputs (depending on the model relays @10A or transistor outpust!!). The pre-programmed function blocks make things like PID a breeze. Plus you have the advantage of being able to have Limited human-machine-interface, as messages can be programmed on the front display. Some models have a real time clock built in too for those early morning pre-heats!! The other thing to remember with them is that they are expandable for more I/Os.

Good Luck!!

 

[Tony]

I like the idea of leaving the temp control ect to electronics and leave the brewing to me.

I have a PLC, access to scada software, you name it but i think i will leave mine with some manual aspect to it.

Its fun being able to get a feel to your system and tweak it to suit the beer.

and gives me a great excuse to hang out in the garage drinking beer with THAT SMELL......... the AG SMELL!!!

i love it.

I have said it on here for years...........true PID control is not needed for us small scale brewers. ON/OFF control works fine and is accurate enough for the small quantities we deal with compared to heavy industry dealing with megaliter tanks th heat and cool.

just my opinion though.

I have a Eurothern 2208 True PID temp controller worth around the $800 mark sitting around unused because i dont need its capabilities.

im hoping to get hold of a gas regulating valve with 4-20mA input to run the gas control under my water purifier. it would be good for that i recon but the on/off holds the brew rig steady.

cheers

 

[kirem]

I have said it on here for years...........true PID control is not needed for us small scale brewers. ON/OFF control works fine and is accurate enough for the small quantities we deal with compared to heavy industry dealing with megaliter tanks th heat and cool.


im hoping to get hold of a gas regulating valve with 4-20mA input to run the gas control under my water purifier. it would be good for that i recon but the on/off holds the brew rig steady.

cheers

I am in much the same boat, I have access to industrial control equipment and will probably use it down the track, but now I am still deciding on how far I want to take my automation. I still get the brewing aromas on brew day but have time to do other stuff around the garage/brewery and if I get called away I know the system can look after itself for a while. I suppose brewing means different things to different brewers. I like a system that has good control and repeatability and allows me to tweak recipes and see the difference and comfortably say that the brewing process didn't change. I know others like to watch thermometers etc.

I think that my PID controller does a fantastic job in controlling the HLT/heat exchanger element to hit a target temperature, something simple ON/OFF will never achieve in the same time frame and degree of accuracy. An on/off controller that can't prevent overshoot or takes forever to hit the target temp will either denature the enzymes with the overshoot or take forever to get the required mash temp and god help if you want to do step mashing. IT is just my opinion, but I have tried using simple on/off controllers on my setup and for me they are not a pinch on my PID controllers. In fact I class the on/off controllers as failures on my system.

So you have two different opinions from brewers that work/have worked professionally with the PID algorithm. My advice is to try both controllers and see what works for you. My on/off controllers found a home in other parts of my brewing process.
PID is nothing special just an algorithm, it is how you setup up the variables within the algorithm that make the difference between an expensive controller just lying around and a very powerful controller.

Tony, most purifiers will say PID capabilities won't work on a still. What temperature are you trying to control, still head, wash temp, cooling water? I would be very interested if you got a PID setup to work. I have tried and done a lot of reading on it and ended up with a sutronics burst fire controller for my 3.6kW element. My still head is matched to 1500W (calculated by vapour speed and cooling capacity) so I use the full 3.6kW to get upto temp then back it off to 1.5kW. I then adjust my vapour control valve to the product take off speed.

 

[Tony]

I havnt tried to purify water yet..... my car battery is still full but when i get to it it will just be a simple gas burner under the keg turned right down
I was going to try it with head temp and monitor cooling water temp. I have read the same and most seem to think that a good old glass thermomiter is best

maybe we should get back to subject and talk purification in PM

I have thought about installing PID to my HLT. It overshoots by about 2 deg when if first heats up from cold but once its at temp it only really moves by .3 deg over or under setpoint and the temp of the return wort to the mash doesnt move.

It all depends on how your system is set up. The length of pipe in your herms......... if your usind a RIMS........ volumes, flow rates, there are lots of factors. My system works well with On/off but if i changed it to control the HLT temp relative to the return temp of the wort to the mash i would need PID. Only pronlem is i need a SSR with a 4-20mA input to regulate the power to a 3600W element.
Not so sure where to get one cheap

cheers

 

[Zizzle]

SSRs are the only way to go unless you like replacing relays once the contacts have burnt out.

Aren't typical relays are rated for at least 100,000 cycles when switching their full rated inductive load?

Even if my code causes a few cycles during a brew, that is a lot of beer before having to replace.

These aren't industrial applications we are talking about. My setup would be lucky to be used more than a couple of times a month.

SSRs were about 5 times the price when I got my mains switching relays.

 

[Nauticaldisasta]

Aren't typical relays are rated for at least 100,000 cycles when switching their full rated inductive load?

Even if my code causes a few cycles during a brew, that is a lot of beer before having to replace.

These aren't industrial applications we are talking about. My setup would be lucky to be used more than a couple of times a month.

SSRs were about 5 times the price when I got my mains switching relays.

Yes, True.

The main advantage with an SSR is for PID loop controlled heating where when the process variable becomes close to the setpoint variable, the switching becomes more frequent to avoid overshoot.

In a standard relay, especially one that has a contact rating of 10A (really designed for control switching not a power switching situation) you will expect to see the contacts burn out if you are using a 2400W element. If you use a small 3 phase contactor and parallel the contacts for 240V you'll be OK.

Look around, especially OS you will find cheap SSRs.

I only recommended them for a longevety point of view. Hate for the system to go down part way through a mash!!

HTH

 

[ArnieW]

Yes, True.

The main advantage with an SSR is for PID loop controlled heating where when the process variable becomes close to the setpoint variable, the switching becomes more frequent to avoid overshoot.

In a standard relay, especially one that has a contact rating of 10A (really designed for control switching not a power switching situation) you will expect to see the contacts burn out if you are using a 2400W element. If you use a small 3 phase contactor and parallel the contacts for 240V you'll be OK.

Look around, especially OS you will find cheap SSRs.

I only recommended them for a longevety point of view. Hate for the system to go down part way through a mash!!

HTH

I'm with 'Nauticaldisasta'. I vary my power for PID control, and that effectively means a lot of switching. Simple with SSRs though.

 

[ant]

Well, I got the temp controllers sorted, and some nice hefty SSRs to go with them.

So now I have two new questions for you, O doyens of things electronic and logic based

Firstly, Im getting to the point that I now need to think about the smarts to drive all this stuff. Ive decided Id like to go a PLC / ladder logic type route, and knowing there are several folks onboard the forum here who know these beasts intimately well, Id really appreciate some advice on them. For starters, how much smarts do I need? Are there brands and/or models to look for/avoid?

My thoughts on process flow are in the attached.
View attachment Process_Drawing.pdf
Secondly, does this unit look the goods as a flow meter? I couldnt help myself when it came up even though its 3/4 and I really wanted 1/2 to match the rest of the system, but it was an awfully good price. It's the ANC12 in the catalog.

View attachment COXANSeriesrev.pdf