GoAway Senior Member Joined: 19 Mar 2004 Posts: 65 Location: dregs Expertise: I love coffee
Posted Thu Mar 25, 2004, 2:40am Subject: Re: all this PID silliness for $10
This is book-length, I've drank too many shots. Hey look, when I say I don't believe a PID Temperature Controller is more than "geeks gone wild" don't get too defensive. It's just an opinion and the only correct one - mine. And hey SHUT UP shut up I'm willing to test it. :^)
But when people like Trey tell you: "These are all La Marzocco machines and all have additional PID boxes for temperature regulation/read-out. However, even on this (expensive) equipment, the temp will still fluctuate, and their is no way to have the temp exact all of the time." Hmm. Of course he's right. And is still doesn't address why it supposedly makes a better extraction.
Notwithstanding that a thermocouple probe is only accurate to about 1% C regardless of controller, and most PID boxes are below that (~3%). By the way, you have to sum all error sources. So just because you set 202 F doesn't mean you'll get within 10 degrees of it, in fact there's really no way to truly measure what the temperature is unless you use a more accurate method. (and tiny little platinum 1/100th degree accurate RTDs can be more expensive than your espresso machine and renting the calibration equipment might require selling your car.)
Thermocouples have one advantage over RTDs and all other temperature measurement options - speed. Although most exposed tip or grounded junction T types are slower than a K, they are the most accurate and least error/drift and only one probe has more mV range (ie resolution: aType E). I'm confused why people want J here. Iron rusts. Iron releases heat poorly causing a really bad time constant. But ok, moving on. Because having something than can only be updated every 15 seconds is useless to a process that only takes 30, we'll stick to thermocouples even J ones. (are J calibrator units cheaper? I'll research more.)
Let's take Greg's landmark post as a guideline. Using a Keithley 2001. -DAMN- That's one gorgeous sexy meter and any electronics geek would kill for one. Even so refer to Appendix A: Temperature (Thermocouple) for a Type T: resolution is 0.1C and accuracy is +/- 0.5C with a calibration error of +/- 0.5C. A type T probe from any top-of-the-line manufacturer has a probe error +/- 1.2C in the 0-150C range... Don't listen to Greg when he plays it off that he's "not an electrical engineer" - he's frickin' lying! He just means he's not holding a degree in the field. :^) Or he's got friends in low places.
THIS IS EXCELLENT! This is probably more accurate than any non-RTD, non-field-calibrated PID temperature controller is going to be by a longshot. By comparison a $350 Fluke 189 handheld with a type K probe has 0.1C resolution also but it's accuracy is about +/- 1C PLUS 1 % of the reading, and +/- 1C error. (and considering to just calibrate a Keithley costs more than a 189, this is quite good.) This is about what a good PID temp controller will do. And it's the best I can do without borrowing/renting equipment.
Nonetheless even with a $3000 meter and a fast response Type T thermocouple there's no way to tell beyond +/- 4.7 F... so if a highly calibrated very expensive measurement device can vary nearly 10 degrees at the extreme, what's the point? Now thermocouples in general and T type specifically are very accurate on relative temperature changes but we're discussing absolute. TWO OH THREE POINT FIVE Fahrenheit? Someone ask Mr. Schomer what the hell he was using to measure that and what it was calibrated against. :^)
I do understand the point. Stabilizing the temperature. Sure it might vary +/- 5 F. (bell curve says only unlucky folks will be at either extreme.) But it will be stable and consistent. So while your specific setup may be off by -3.131 F it will pretty much stay there. Yet shooting for 202-ish still leaves much room; a stable 199-205 F? The question is does it matter? That's still a huge range compared to what people must think a PID setup does. I'm having a hard time beliving you'll do better than a stock Silvia with it's antiquated mechanical thermostat. I'm not saying the right temperature is not important. Sheesh. Yet it is like saying you cannot cook well in an oven set for 350 degrees but actually measures at 346 from time to time when the element is cycling. But fine. I cannot speculate beyond a certain point and we're at that point. So I will get a commercial unit first. Looks like I can pick up one off of Ebay for under $50 plus a probe. I'm daring it to make a difference, too. So if it does... crap on a stick.
None of this invalidates we can design and build one very cheaply. We're just discussing if it's worth doing. ----------------
Hey Greg, yes I've read your test results and the many follow-ups. Multiple times. Thanks!
>> crop of steam toys?
Ok I'm assuming again here, considering where this conversation is taking place. If it says Black & Decker, DeLonghi, Krups, Mr Coffee, etc on it and you think I consider it "an espresso machine" then we're having two different converstations. Companies that sell units in the thousands have a different customer mentality than ones that sell in the hundreds of thousands. I DO think that Gaggia and Rancilio care. ECM? Sure they do.
>> means that there will be a large temperature overshoot
Yes exactly, this is the type of converstation I want to have! Someone on here said something to the effect of turning his steamer heater on for four seconds and then pulling the shot. I'm thinking to myself that the thermal conductivity of brass and water are known quantities and his 4 seconds won't mean diddly, even at the end of a 28 second shot where supposedly it's compensating for the temperature dropping but that little "oomph" of extra heat will maintain constant temp. Even if slightly effective it will only sustain a temperature that was going to drop by ~1.8 degrees or so. Big deal. If your epsresso flavor is that delicate you need to invent a different extraction method. Anyone that thinks 203.5 F is the only place to extract is a phuCk1nGfr3@k.
>> nontrivial. So just changing thermostats doesn't cut it.
Sure it would - but as you say it's nontrival. You aren't just picking one that fits at a value you think would work. It would require installing and sampling. Just manufacturing tolerances alone says you should be able to get a bagfull of same-value thermostats and find ones that make consistently hotter extractions than others.
>> unless it's made available commercially. Guess no one's stepped up to that, but maybe you're gonna?
There is no way in hell I would do this as a commercial product. It's D.I.Y. and open source code developed only on open source or I would not participate. Which brings up another question, how many would be interested? I could do it by myself for myself but I'm not convinced I actually care that much. (or it matters that much! Let the testing commence.)
>> I'm not particularly interested in building electronic devices
I am. It might be entertaining just to do it. I'm hoping this thread will inspire other coffeegeek electronics types to chime in. This is a fairly simple task for a micro, in fact interfacing to a temperature sensing device is one of those Application Notes tutorial examples just like "Hello, World!" in programming language tutorials. (temperature sensing is big in the controls world, gee really?) The most time-consuming part would be designing the user interface and wiring a display... if you just wanted a fixed temperature like 202 F the circuit would be as big as a nickel and have maybe 8 components. Then separate files to program the micro with per each unit's compensation values. But I know for a fact that people like lights. Bright flashy ones. :^)
I don't want to to it alone. I don't want it to be "mine". I don't want to support it for the rest of my life. A group effort only and community supported and zero copyright issues.
>> By the way - I don't know anyone who has removed their PID from their machine after trying it out.
So? That's completely invalid. Human (err male) nature prevents it. Something so subjective, esoteric, exotic? COOL? Of course not. You ever met an audiophile with a $10k turntable setup? I don't even believe in it's benefit and I'm not going to remove mine; the pinnacle of coffeegeekness? I'm thinking of chroming the case and adding extra blinking LEDs for no apparent reason.
:^)
Now, now; perfectly symmetrical violence never solved anything!
Koughy Senior Member Joined: 29 Oct 2003 Posts: 41 Location: Storrs, CT Expertise: Intermediate
Posted Thu Mar 25, 2004, 5:08am Subject: Re: all this PID silliness for $10
Very simply, I have better things to do than spend alot of time fiddling with custom electronics when I can pick up a commercial unit and have it working in a few hours. (and I am not an electronics guy) The benefits are subjective I guess, I saw a huge difference, but I never liked temp surfing, pain in the neck to me. I have mulled over plans to build a custom heat exchanger to install in the boiler of my silvia, and install a rotary pump, or an air driven piston pump of my own design. (I am a mechanical guy) Will I do it? depends how bored I get I suppose... right now I get nice espresso out of the machine and I am happy with it, and I have a motorcycle completely scattered across my kitchen that requires my attention (and a car in the garage, and a van outside, and god knows what all) I would encourage you to explore your custom controller, sounds cool. Go into buisiness modifying machines and reselling them to others who will pay for it. Koughy
MOSFET Senior Member Joined: 31 Dec 2003 Posts: 376 Location: Long Island, NY Expertise: I like coffee
Espresso: Linea Grinder: Mazzer Mini Vac Pot: Hoover Drip: Post-nasal Roaster: Perdue Oven-Stuffer
Posted Thu Mar 25, 2004, 8:21am Subject: Re: all this PID silliness for $10
No one should feel like they're a stooge for having bought a PID controller. It's a great application on these machines. There should also be no concern over accuracy or thermocouple. A type K is perfectly fine, and you can calibrate the PID / thermocouple combination using one or two points. The two points would be ice water and boiling water. It's slightly more accurate for espresso users to calibrate only at one point: 212F. If you want to go nuts, find the right boiling point for the current weather conditions in your area, and boil some water. Filter the water if you like. Then calibrate the unit so it reads properly. If you do this you will be well within one degree F of true temperature. The PID instructions would show you how to do this. They will probably say to let the unit warm up for a few minutes first. However, most people won't care about absolute accuracy, just consistency and ability to adjust temperature. The PID is great for that, and the amount of overshoot is adjustable.
gscace Senior Member Joined: 19 Dec 2001 Posts: 237 Location: Laytonsville, MD USA Expertise: I live coffee
Espresso: La Marzocco Linea 2AV, Astra... Grinder: 3 Mazzers Robur, Kony,... Vac Pot: Cona D, Hario Nouveau Drip: Technivorm Roaster: Has Garanti 1kg. electric
Posted Thu Mar 25, 2004, 8:28am Subject: Re: all this PID silliness for $10
In reply to Andy S's post:
gscace Said:
Is it worth it? The data is on usenet. Search google groups for Temperature Study of my Sylvia (loooong). Note that Silvia is misspelled. Also search for articles on proportional control of sylvia and PI control of sylvia....I did the measurements in 1991
Holy cow! 1991!!!!
-Andy S.
Yeah, I'm time travelling and a total space cadet. Add 10 years to that as you know (2001). I'm time challenged
gscace Senior Member Joined: 19 Dec 2001 Posts: 237 Location: Laytonsville, MD USA Expertise: I live coffee
Espresso: La Marzocco Linea 2AV, Astra... Grinder: 3 Mazzers Robur, Kony,... Vac Pot: Cona D, Hario Nouveau Drip: Technivorm Roaster: Has Garanti 1kg. electric
Posted Thu Mar 25, 2004, 9:16am Subject: Re: all this PID silliness for $10
Hi:
This is in response to GoAway's post on the 25th:
Actually we make pretty accurate measurements here (NIST) with thermocouples all the time. The requirements for doing so are to have a reference junction that is at a known temperature (ice point works good), have a sufficiently accurate voltmeter, and sufficient purity in the wires. Accuracy better than 1C is quite easy to achieve. But that ain' t gonna be my point here. What is the issue for control purposes is reprocucibility, not accuracy. Schomer's 203.5 degrees is jus his number for his blend in his machine. In fact, most Silvia people set their boiler temps a little higher than this to get a little less temp than 203.5 at the coffee. The reasons for this are due to Silvia's design, whereby the group is hanging off in space and cooler than the boiler. And yes, this does contribute to variability in brew temp dependent on duty cycle. I use my taste buds. Once I find out what the blend likes for temps, I can reproduce it all day long since the parts of the system are constant and behave the same over time. It ain't absolute accuracy. It's reproducibility of the same starting point that's the good thing the proportional controller provides. And it's also the ability to quickly and eaily dial in a new setpoint. I got given some Malaber Gold last weekend at Coffeefest and it likes brew temps a bit hotter than the straight Harrar that I've been drinking. Takes about 10 seconds to punch in the new setpoint. And the difference is measureable in the tastebuds.
The argument that absolute temperature stability is needed to make good espresso is one that ain't settled yet. My experience is that it might not be true that absolute stability is important, but absolute precision seems to be. None of us have enough machines , or machines with variable temperature profiles that can settle the first argument, but I think it's reasonable to assume that improvements in consistence are a good thing. One other point is often missed in these discussions is that proportional control only improves the shot group. Once brewing starts, system characteristics take over. for instance, feedwater comes into the top of the boiler, the heater turns on, etc. The proportional controller just improves the precision of the starting point. Thinking that absolute temperature uniformity is achieved by instituting proportional control is incorrect. You can certainly examine the ability to control other factors such as group temperature, water flow rate throught the coffee, in order to come up with an idea of how much temperature start point precision is useful. In my experience, garden variety proprtional controllers such as the Fuji PXR3 are complimentary the consistency of a reasonably skilled barista. As you know, you can buy much better and more accurate controllers than the PXR3, but I don't thing their use is of any benefit. On the other hand, I can certainly see the difference when I have access to less precision. My next door neighbor has a box stock Silvia and I roast coffee for him. There is a very noticeable difference in the consistency of the cup produced by our two machines.
WRT on / off control in machines where the thermal mass of the heater is large in relation to the thermal mass of water in the boiler : As you know, the heater has to be a good deal hotter than the water to get heat to flow from the heater to the water at the rated power of the heater 800 Joules / Second (Watts). When you shut off the heater, the heat contained in the heater dissipates into the water, even though no energy is being supplied to the heater, until the heater temperature drops to that of the water. So the water temperature increases significantly over the max temp limit of the on / off controller. In the case of the proportional controllers, the heater is on for such a small fraction of the time that the temperature of the heater doesn't get significantly higher than the water, so the temp stays in equilibrium in steady state conditions, and has less overshoot on recovery than would have been the case with on / off control. I think you know that already.
Regarding your skepticism regarding the benefit - I don't believe Schomer's number is hard and fast at all, or even right necessarily. I've certainly demonstrated to my own satisfaction that proportional control improves consistency significantly and that it is worth doing. Try it for yourself and see if I'm right or not. Shouldn't be hard for you to do.
And no, I'm actually not an EE. I'm a mechanical engineer in a metrology candy store. I s'pose I could learn to build a controller, and the open source thing is a nice idea, but there's a limit to how far I'm gonna go to gin up solutions. I don't make my own dirt to shove into holes in the yard when I can get satisfactory dirt from my local satisfactory dirt supplier.
Posted Thu Mar 25, 2004, 11:20am Subject: Re: all this PID silliness for $10
You know you're a coffee geek when you start to understand coffee engineering speak........ 6 months ago, most of this post should have gone right over my head....
Here is my 1 cent on this issue.. ( trust me, I don't have 2 cents worth)... You can argue about defining accuracy, error correction, etc. etc. until you are blue in the face,....You can dissect the whole espresso process until einstein turns over in his grave...
I boil down this discussion to the one point Greg touched upon... It doesn't matter what "number" the PID displays, whether it is 202.5, or 97... the point is, if you can repeatedly hit that number, it gives you a consistent starting point from which to make adjustments.
Once you have a starting point, you can use the best " meter" of all, your tastebuds, to make smaller adjustments from that reference point.
Right now, the only indicator we have is the red light that goes off .. ( or on) telling us.. " You MUST make coffee now or the world will end!" The problem is, we know that red light lies...We know that red light is full of doody... We have no respect for that red light, so we learn to ignore his message, because he is just a silly, evil, little red light..
On the other hand, we respect the PID... he has not lied, he has not decieved.. and until someone proves that he is in effect yanking our coffee legs, we will continue to respect, and possibly worship the PID, and his warm green LED tones... he is our friend... ( albiet an expensive friend).
So yes, you can get obsessed with tenths of degrees... but ultimately your intuition and coffee instincts..( did I really say coffee instincts???) will be your guide to shots that are to your liking.. But, the technology will help you get back those shots more consistently..
We cannot control all the variables... We can roast our own coffee, but we'd probably have to grow our own beans, filter our own water, grind in a humidity controlled environment, adjust the speed of our grinder so as to not produce too much heat, weigh out our dosage to 1/100th of a gram, tamp to 29.567 lbs, etc..etc...
But everything I've learned in preparing coffee is about trying to make each variable more repeatable... Not perfect.. but repeatable.
As for Goaway's "project" . If you can produce a device that can provide that temperature "reference point" cheaply, whilst allowing the user to make minute adjustments, then some of us may elevate you to coffeeGOD status..
All we need is consistency in our "starting point"... from there, we can screw up fine on our own...We don't care about platinum RTD's.... all we want is cheap and good... am I right??? am I right???
oh oh.. I better go.. the red light is calling me.. (running)
GoAway Senior Member Joined: 19 Mar 2004 Posts: 65 Location: dregs Expertise: I love coffee
Posted Thu Mar 25, 2004, 2:08pm Subject: Re: all this PID silliness for $10
See that's the problem. Up until about two weeks ago I was fine with the process. By fine I mean 15 years of my daily espresso-making life have gone by and I've had a few different machine and done some pretty silly tests (like parking a gaggia classic next to a rancilio silvia and using both) But I was with scooterboy. It's not that important. I can make shots extremely well, hell I've had 10,000+ shots of practice. The red light never ever called me. I walked to the machine, ground some, tamped it and brewed it. As long as the beast was on 10 minutes or so, it was ready. Not only did I not care what part of the cycle it was at the idea that it could bother me was ludicrous. IT'S COFFEE.
But something in my brain clicked, snapped, screamed. Too late. So here I am again doing stupid crap.
Excuse me but I DO filter my own water and with a setup that rivals a bottled water plant. 6 stage? submicron for the final? two taste two chemical two sediment? THIS is how it starts, doubt. I don't know what I read at that specific time that got me considering doing a PID rig. Then debating internally it's merit to the point of reading up on all the archives. To researching controller units and probes, getting bogged down in engineering specifications for things grossly overkill for coffee. To the point of getting upset at the price people were willing to pay. That was the bad point. This is not an electonics forum where an off-topic thread about espresso started. My bad. I thought truthfully there would be 90% electronics geeks responding. I really did.
We should let this die I'm guessing. If the initial PID test works out I'll move the development conversations to somewhere like electrotech's forums where they probably don't care about coffee but will have lots of ideas on controlling water temperatures. I'll put the link here for those wanting to offer input but who have zero interest in writing code. (would you prefer blue or purple LEDs?) And I'll start a whole new "come say I told you so to GoAway" thread if Greg and the Belivers are correct. :^)
Now, now; perfectly symmetrical violence never solved anything!
Posted Thu Mar 25, 2004, 5:11pm Subject: Re: all this PID silliness for $10
recently, GoAway wrote;
I'll put the link here for those wanting to offer input but who have zero interest in writing code. (would you prefer blue or purple LEDs?)
i would prefer blue LEDSs because i didn't know they came in any colour other than red until i bought a bluetooth phone. and becuase it would match my bluetooth phone. i also don't know how that works. LOL.
i didn't realise your project would result in cool LEDs being attached to my silvia. in that case i'm all for it. :)
This is where my electrical knowledge lies, too! Another vote for blue. . . though, it's irrelevant. I should have my PID hooked up by then, and I doubt that I'll be replacing it. :-p
gucciago Senior Member Joined: 6 Apr 2004 Posts: 51 Location: Palm Beach,FL Expertise: Pro Roaster
Espresso: 1990 FAEMA Compact 85 / UNIC... Grinder: MAZZER Major with DOSER Vac Pot: N/A Drip: N/A Roaster: Roaster / My own
Posted Wed Apr 28, 2004, 3:10pm Subject: Re: all this PID silliness for $10
GoAway Said:
"but I highly doubt everyone has the equipment/skill to produce something like that"
Yea? I highly doubt most people understand how electricity works. At the most basic level. Or an internal combustion engine. Doesn't stop them from using them. (How many instant vegetarians would we have if everyone had to slaughter what they ate, for that matter?) You don't have to understand nor have the skills to design or assemble it. There are electronics geeks that do. That just happen to drink espresso. And besides there's other hobbyist fields that already have these DIY types of temperature controllers: Ceramics kilns, glass blowers, smelting furnaces, etc. We could adapt an existing project although truthfully I don't see any serious design hurdles. I threw that out off the top of my head when I was researching what this PID stuff was, how many were serious about it. I'd think you were all a bunch of whacko nutjobs except that Schomer is where you got the basic idea from. What I outlined is probably not the best way to do it. I was fishing for others interested enough to discuss it.
Check out some of the other community-driven DIY electronics projects. I was thinking something along the lines of the MegaSquirt EFI computer. The PCB and a component list made available, then the community at large could help put photos and documentation of installs, help troubleshoot, make software modifications, faster response temperature probe solutions, etc etc. Where a core group actually does the work but everyone can benefit and provide input. A few devotees sell assembled units for those that don't know the business end of a soldering iron. (supporting the notion that for every capitalist thinking "time is money" there's a geek thinking "knowledge is power" - not mentioning capitalist geeks thinking "knowledge is money".. :^)
Here's the one basic premise I haven't picked up from the archives: Is it just temperature or is it the total control of all variables? For example would a PID believer think a lever/piston machine is useless as the human-supplied extraction pressure is too variable? Believer. Sounds like a religon. Wait, a subsect of the overall espresso religion... we're all zealots anyway.
PS: (Atomic_Dave) Point #1 in your list. That is for a replacement thermostat costing just a couple dollars, not the controller I described. The controller be balls-on accurate as any PID you can buy down to the sensitivity limits of whatever probe is used. No, that is a thermostat just like the one your unit came with only with a lower differential. (technospeak for a narrower range between the on/off trip points.) Someone interested in raising and/or stabilizing the temperature after surfing a bit might think this is more feasable, it's both simple and cheap. But I do not see it discussed.
Well.... I PIDd and considering a pump replacment with a TESLA PUMP!! lol hmm... idea... :-D
I did my PID for 1 main reason.... KEWL!! and then I could SEE whhat teh temp was if I were trying differnt home roasting as to "SEE" any differences... Chemistry is my game...well.. was in University... now just fun...lol
OH! and my next project IS making an espresoo macnine... seems easy enough... just wondering why the NEW La Marzoccos come WITH PIDs... hm....
my only thing is... I can in no way set my PID to 230deg!! SHEESH! burns my coffee to ash.... temp coming out of portafilter is about 210deg!!! that is EXPOSED!!! I bet it would hit the coffee at about 220 at least.... this is all in fun and education.. maybe in thermaldynamics... it is just kewl....
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