Posted Fri Jun 22, 2012, 11:47am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Thanks for testing and posting - but I think you keep misunderstanding my suggestion. I want you to try it without using that alarm function at all.
I simply want you to set the PID to a higher temp (since you are worried about steam, try 222-224F) - do a cooing flush (about 1oz) - wait 60 seconds and pull a shot - measure the temp in styrofoam cup. (please don't burn your fingers)
Ideally it should be just as simple (really it should be much more simple since the PID will do most of what I'm doing) as kicking the PID up to the hotter temp and remembering to do the 1oz flush and wait time (just like the HX folks do). I don't expect it to be a whole complicated routine that would make it not worth the effort when you just want to enjoy a nice espresso.
Sorry, I guess that I really do not understand. I had read most of the posts back over several pages about what I thought you wanted. I thought that you wanted the second set point, not connected to the brew switch. The second temperature is on the alarm function, but is still just a second temperature. It will heat faster than the PID function, but essentially mimics your switching. The machine was heated by PID function to 214F and then the second temperature was selected by a switch, independent of the brew switch. I disconnected that as asked. That second temperature is on the alarm function of the PID, but is now just a switchable temperature. The early math calculations of heat calories, and your experience, show that you need about 50% duty cycle of heat. I cannot see how the PID function will give this, that is why the alarm function.
I did not hit the steam switch, and I did a cooling flush to avoid over heating, even at 223F. The steam switch would be redundant in this test as it does the same as raising the second set temperature, turns the heater on.
I did try different temperatures and moved down to the approximate 223F.
Do you really want the test run on PID function, instead of alarm second set point? I can do that by changing the PID set up to 223, and then down at the end but that is tedious and not on a switch. I do not think that it is a practical was to change set temperatures. I believe that the remainder of the test is as you described it. If not, I am happy to run it again with corrections, if I can understand the corrections.
I may not understand the alarm function ... but I think you said it was ON/OFF which (If I understand what you mean by that) it would stay on until it hits the alarm temp and then shut off. And I think that would overshoot the target temp.
I was hoping to determine if the PID set for a higher temp would take the temp up near that temp and hold it there during the recovery period - without overshooting it the way a T-Stat or a simple ON/OFF function would (but maybe your alarm does do that?)
The upside of what I'm suggesting is that you don't have to warm the machine up for 30 minutes ... you could wake up in the morning, turn the machine on (leave it set at the higher setting) and pull a shot with only 5-10 minutes of warmup and then turn the machine off and go to work. That's what I do every morning and that's how I made the video with the consistent shot temps.
If I'm not actively pulling shots or steaming milk, I turn the machine off.
But we have very different styles of dealing with our machines so maybe I just can't understand your reluctance to have the machine running at a higher temp. Most of the higher end espresso machines, that so many forum members own, are left on all day with the steam boiler running at higher temps than I'm suggesting here.
Posted Fri Jun 22, 2012, 7:25pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
The alarm function has a high and low setting and for purposes of controlling a second set point, I use 1 degree F difference. On until the upper point is reached and then off until it cools to the low. Yes it overshoots and that is why it only took a few degrees higher than the PID set to do the test. I tried higher second set points and got steam, and then still too hot, until the 223F.
"I was hoping to determine if the PID set for a higher temp would take the temp up near that temp and hold it there during the recovery period - without overshooting it the way a T-Stat or a simple ON/OFF function would ." Take it up, yes, but hold it with use, I do not think so.
Using the PID box as PID function as we discuss seems that it could idle up in a couple minutes, but will not quickly recover from a flush of pull. Many posts note that "a PID does not affect intrashot temperature." It is too damped, its purpose of holding temperature without overshoot, or minimized overshoot. If the PID could really maintain temperature, then it should have been maintaining intrashot temperature and be ready for a second pull. It is far too slow at reacting. The reason that it does not overshoot is the damping and less duty time, so less heat calories in for any time period. That is why it will not maintain against cool incoming water and why I use the alarm function.
I am not sure how the test as run does not already demonstrate basically what you wish, idle at under boiling, second set temperature on a switch, flush and pull, and the seeming ability to get a timely second shot. While there is significant overshoot on the first few run ups, the overshoot diminishes as the temperature settles around the alarm limits. Greater temperature differentials leave the heat on, and then off, for longer intervals.
The PID does not have 2 PID function set points, and I have not seen that in the inexpensive generics. I am not sure about the more expensive units. I can scroll the PID function temperature up to run the test and then scroll it down for idle, or as you suggest, leave it at steam temperature and use cooling flushes to adjust. Cool flushes and temperature adjustment require more technique and learning, and I was hoping to use the PID to do the work. While a test can be done scrolling the temperature set point, a switch is the practical way. I believe from what I read about PIDs that most people use the PID to set an idle temperature such they can get a pull at that set without much technique. In addition, that is how they adjust a degree or two to change brew temperature for different blends. I have no difficulty with X seconds of steam switch and Y seconds of rest, and then pull the shot.
You may be thinking past where I understand, so I hope that you get a PID to try it. You can get a generic or Auber PID and SSR, no box and no wiring very cheaply. You obviously have thermocouples. The wiring is simple and there are enough diagrams on the internet to show how it is done.
Posted Fri Jun 22, 2012, 8:04pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Did you realize, from watching the video, that I am NOT doing any heat control during the shots?
I am simply getting the metal of the boiler somewhat stabilized near the set point (what the PID should be able to do easier and better than I am doing) after a flush and then the 4 seconds of steam switch (and then off) and then start the shot. I don't touch the heat after that until the shot ends.
There is no need to input any heat during the shot or try to hold the boiler up at the set point during the shot - that is the whole point of having the higher set point. The boiler being so much hotter than your normal point (and the water inside not having had 5-10 minutes to stabilize) is the whole point of my method.
You get the metal outside of the boiler up to that very hot temp and start the shot while the water inside is still not up to heat yet (because of the flush) and if you get these two things right (using the wait time after the flush to determine the starting temp) ... the extra hot metal of the boiler allows the temp control to coast right through to the end of the shot - the boiler giving up that extra heat to the incoming water.
So ... we aren't expecting the PID to be able to hold the boiler steady at the higher temp while the shot is pouring ... we expect the boiler to have cooled by the end of the shot - that's why I was hitting the steam for several seconds at the end of the shot, the boiler was down around 212F or so at the end of my shots but the brew water was still at 198 or so.
Your PID should be trying to bring the heat back up (probably faster than me because it will have started while the shot was still pulling) .... so then you just have to find the correct wait period after the shot to get your desired brew temp.
At least that is how I visualize it working ... with the PID it may be a whole different routine that I am imagining.
Posted Fri Jun 22, 2012, 8:52pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Yes, I realized that you were not inputting heat during the shots. I was actually surprised by that and noted it.
I get that the metal of the boiler is super hot and adds the calories and have commented on adding a time factor to the mix, not just calories in and cool input, but timing.
I thought that we wanted to pull a second shot in about 60 seconds, the timing in what I did, and what you did on video. Clearly adding enough time will allow for a second shot. Supposedly, if I do nothing with the alarm or PID temperatures, the machine will be ready for a second shot in about 4 - 5 minutes, back to a near original stable temperature (The early mentioned Auber data). An early shot has been the problem and I did not understand that you were "allowing for the correct wait period after the first shot." Yes, I believe that the PID function will get the water hot enough if the temperature is set up as you described and allow more time.
I wish that second temperature was switchable. As long as I have to flush, cool and manipulate, why not use the switchable alarm? If the second PID temperature is above boiling when stable, then why worry about overshoot? Overshoot is mostly on the PID sensor at the boiler stat location, not much on the Polder, which does somewhat mimic yours.
Posted Sat Jun 23, 2012, 12:50am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Supposedly, if I do nothing with the alarm or PID temperatures, the machine will be ready for a second shot in about 4 - 5 minutes, back to a near original stable temperature (The early mentioned Auber data)
That would get you the starting temp ... it doesn't get you the stability during the shot. Getting the stability during the shot comes from shifting away from the Auber approach of getting the water and boiler to equilibrium --- going with the hotter boiler/cooler water is what gives my method the temp stability during the shot. It has a secondary advantage of being able to pull a shot with proper temp without the long warmup period ... and that also gives you the ability to pull a second and third shot without a long recovery period.
But even if you are only going to pull a single shot - it will drop less in temp with my method (Auber shows the shot temp dropoff in their graphs).
Posted Sat Jun 23, 2012, 9:10am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
I mentioned that time course of 4- 5 minutes because, if I understood correctly, that is where you get back to starting temperature after a shot using a PID. I recognize that you would not get the perfect shot, and in fact they found about 18F intrashot drop. I was just trying to establish that there was a normal PID recovery time at about 4 minutes and we had been aiming at about 60 seconds. Intrashot stability is addressed mostly easily by pre-shot steam switch. The PID with pre-shot steam switch gives a pretty decent shot, and if there is a 4 - 5 minute wait, then a second shot. The "Auber method" was a study noting parameters with the PID, not suggesting how to get the best shot and did not look at adding heat, pre-shot or intrashot.
PID set at desired stable temperature for a cup starting temperature of about 200F, then added pre-shot heat on by steam switch is probably the easiest way to get single pulls, IMHO.
The discussion and testing is less about single pulls than how to get a timely heated second, or more, pull. Clearly your method is proven and works well, if the user has the technique. My desire is to eliminate as much of the technique as possible and let the PID do as much as it can. I think the the techniques and timing is difficult to master at your level and takes a lot of experience. I hope that the PID can shorten the learning curve. At that brings us back to a similar spot, getting more than one pull using the PID.
I will try the PID as you suggest, but I am not sure that I can give the best result. If I understand correctly, I will have to adjust the PID to a higher than idle temperature, then wait undetermined time, and then if I do not get the desired result, then adjust the temperature upward or wait a longer time between pulls. that is where the 60 seconds came in, and what I recall you were doing on the video. Do we have an upper limit of reasonable time between pulls? That is where I noted the "4 -5 minutes." I hope for 60 - 90 seconds. Further instructions or comments? Again it may be a few days.
I may be less than enthusiastic about this "unstable PID" method, mostly because of the impracticality of moving PID temperatures. I did think of a way to make it more user friendly. If I know that I am only doing a single pull, then I do my standard way and leave the PID set. If I know that I am doing multiple pulls, then I can just go to the high set on the PID and check it after 5+ minutes. If I understand the method, it does not need a stable fully warmed temperature, but fairly balanced heating and cooling inputs, cooling being the pull.
2 PID set temperatures, PID idle and PID high on a switch. I think that if your method works, then I would probably have 2 PIDs switchable so that one of the other is operable, DPDT switch with on-off-other on. Each PID would have its own sensor, probably at the same location, and running to the same SSR but dioded to keep the SSR input separate.
Posted Sat Jun 23, 2012, 11:31am Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Another observation while doing the test. I started using my Styrofoam cup and preheated digital thermometer more often, to get back in practice and to try to find some reproducibility. I measured idle brew water temperature with the PID at 215 F and got about 201.5 – 202F. If I measured just after an actual double pull, with about 4 seconds pre-shot, preheat with the steam switch, then I got about 195F using the Styrofoam cup to measure brew water post shot. That was with the Alarm function of the PID “helping” by coming on with the brew switch. With that shut off, the same test with pre-shot preheat gave a cup temperature of about 185 - 187F. Calories of heat and in and calories of cool water in only cancel over the correct absorption time. That timing is difficult to determine and may be best avoided by the Andy preheat and flush method, if pulling more than one pull. I will try another second of steam switch and another second wait before the shot to try to prevent as much temperature fall intrashot. Unfortunately, too much heat in or too long a delay will raise the starting temperature to overly hot.
I also found an interesting Polder thermometer observation. My Polder temperatures were in the 230F range, similar to what Andy had in the video (more like 235F). The whole boiler is the heat source. The PID sensor is overwhelmed by being in the center of the heater, brew stat location, which allows it to sense and act quickly, but gives poor boiler temperature. Andy’s location of the Polder thermistor may be better, but as long as the boiler is full and not steam sitting on top, then the boiler metal, away from the heater elements, may be similar top and front, at least I was getting similar readings. I am not suggesting exact readings, the thermometers are not that accurate and are not calibrated together, but similar Polder temperature. In fact, that is one of the things that I wanted to know about Andy’s multiple shots and I used it as a target.
Yes ... but I am not trying for that type of stability. The 4-5 minute for Auber stability is getting the water to an equilibrium with the boiler and my concept is to not have them at equilibrium so that the hotter boiler will continue to give up more of its heat to the cooler water later in the shot.
Intrashot stability is addressed mostly easily by pre-shot steam switch.
If that is working perfectly for you - then there is no need to look further. My suggestions are based on what is working for me and the advantage of quick warmup time in the morning and quick recovery time are high for me - the disadvantage you perceive of idling at a hotter temp is one that has no weight for me - so for me there is no downside. (I turn the machine off when I'm not pulling shots - so no extra energy costs from idling at the higher temp)
My desire is to eliminate as much of the technique as possible and let the PID do as much as it can.
Here we are in perfect agreement - that is the same thing I'm trying to get to with my suggestions. You have the experience with the PID and I do not - so maybe I'm just missing some vital information - but I really think the PID would do exactly what we want it to do if you simply set it to the higher temp and leave it there. I don't see any need to keep shifting it back and forth between two settings. I see no problem with leaving it at the hotter setting, just remember to do whatever volume flush and wait that you find gives you the desired brew temp.
As a starting point - I would set the PID to 225F (10F higher than your current idling temp, right?). Now -- if you turned it on 30 minutes ago and it's been at 225F all this time, you are going to need to do a flush and you'll probably see steam when you flush - not a problem as long as you keep your fingers out of the way - this will warm up your waiting cup. I'd try 1oz flush for starters and try waiting 45 seconds for starters just to see what you get. If the brew temp is too cool, you would wait a little longer (try 60 seconds).
I think I was finding that for 197-198F brew temps - I was waiting about 45 seconds (but I wasn't using a timer, I was just going seat-of-pants from pulling shots like this for months) and for 203F brew temps I was probably waiting closer to 90 seconds. (I almost never pull those hotter shots - so I was just winging it in the video)
You can also juggle the volume of the flush or the PID set temp ... but the best way to experiment is to only change one variable at a time (you seem well versed in the scientific method) ... so I would try varying only the wait time at first. And if you find the wait time is always longer than you hoped for, then try a little hotter PID setting and then try the same series of wait times again to see what you get.
I'm thinking 227-229F is going to be the actual PID set temp - but I'm still suggesting starting lower and testing there and gradually work your way up if needed.
And if you're just sick of all this ... no worries ... you're already getting great shots using your method.
Posted Sat Jun 23, 2012, 12:59pm Subject: Re: Gaggia SBDU Preheat PID Temperature Recovery and Stability
Not sick of it at all. I may get lost about where we are going once and a while but I have learned a great deal.
I would guess from PID threads that I read even before getting the PID that many use the PID as I do, setting a stable temperature and getting a shot from there. To me, that is the simplest method if you have time for warm-ups or use a timer. I also know from many of those threads that intrashot temperature can be a problem that is mostly remedied by a pre-pull heat blast and I believe by using the PID alarm with the boiler switch. That does heat the boiler to a higher starting point for the intrashot. Also not be lost sight of is those that preheat with copper coils.
Your method is all that I have seen so far that clearly gives rapid second pull shot stability. I am not happy with the PID for second shots, at least yet. I will probably not be happy even with the method you are having me try. Happy if it works, but not so happy that it takes significant user skills. Even if it works as I believe you are heading, the user would have to be careful with timing the second and subsequent pulls. Too soon and too cool and too late and too hot. I can get a good single pull by idling the machine, hitting heat for a few seconds and waiting a few seconds and then pull. I am not busy doing other things to distract in those few seconds and it is reproducible. I am not seeing that ease with any rapid second pull method; it is going to be too experience and skill weighted.
The back and forth mentioned with the PID is so that I could easily use it as I do, and then easily change to your method. A switch to a second PID would easily remedy that. The cost of a second PID and thermocouple when you already have a PID and SSR up and running is minor.
I am guessing that the proper temperature PID setting will put me in a 230 - 235F Polder range and you may close with your suggestion. I think that I am banned from experimenting for a few days, wife is getting ready to give a shower. I will be lucky to get my espresso.
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