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Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
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brianl
Senior Member


Joined: 1 Dec 2012
Posts: 473
Location: Chicago IL
Expertise: I love coffee

Espresso: Quick Mill Vetrano DB
Grinder: Baratza Vario
Drip: chemex
Roaster: Behmor 1600
Posted Wed May 8, 2013, 3:34pm
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

Let me know if you come up with any more mods. i'm dying to get back to the electronics. ha.

I usually slurp down the shot before the crema dissipates. However, if it does ill make sure to take a measurement. I will say that my shots usually run 25-30 grams. So I take it that's approximately the same in ml.

When you say preheating -- do you mean instead of you flicking the steam switch before the shot, have it automated? Or is the whole last sentence about the steam?
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Wed May 8, 2013, 4:50pm
Subject: Re: Gaggia Classic PID
 

It was about automating the preheating with steam having it switched on and off as the pre-infusion, or instead of the pre-infusion.  It would be another thing to make electronic though I do not mind the steam switch for that.  Just a thought so that you have some more electronics :)

The weight is close enough to volume that it works for me.  More accurate I'm sure.  Sounds like I am at about 30 - 35 ml and you about 25 - 30.  I may work on down to 25 ml to try it.

 
D4F also at
http://www.gaggiausersgroup.com/
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Sun Jun 23, 2013, 2:05pm
Subject: Re: Gaggia Classic PID
 

Also, I found a nice explanation of PID and edited it onto the first page, but worth repeating here  "PID for Dummies."

http://diydrones.com/forum/topics/pid-explained


A little update on settings and use.  I now have the "brew alarm" setting at 240F off and 241F off and use about 3 - 3.5 seconds of steam switch on and about the same time off before hitting brew.  that will have the PID readout at about 219 - 220F.  That seems to work for 30 - 35 gms of brew out.

If the brew volume/weight is about 50 ml/gms, then about 250F for the "brew alarm" as noted before.  Volume or weight of brew between 30 and 50 gms should use temperature between and adjust to taste. The "on and off" of the steam switch should be about the same.

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Tue Jun 25, 2013, 6:59pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

After reviewing all the great testing people have done and the issues (cooler incoming water, where the temperature sensor is (usually) located, thermal mass, slow heat transfer from the boiler walls to the water, response time, pulsations, etc), I think I've concluded that I will try using an air driven shot.  Ie, heat everything (boiler, water, group) to the right steady state temperature (with PID) and then apply 9 bars of air pressure to the top of the boiler.  Air has very little cooling effect.

I also have some interest in a sinking but almost neutrally buoyant movable divider in the boiler that would separate incoming water (bottom) from outgoing water (top). Less mixing this way (ie, encourage stratification).  But air sounds better.
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D4F
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Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Tue Jun 25, 2013, 8:34pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

Jon, an interesting post, welcome to CG.

I don't think reasonable temperature stability is terribly difficult to achieve. The YouTube video shows the Gaggia to be fairly stable with heat added during brew. Your concept is interesting but I don't have a compressed air supply or regulation available at my coffee station. The big problem with temperature stabilization comes after the first brew. You are still going to have to get water back into the machine and heated. As you develop your concept further you may wish to start a new thread. I'm not sure that I've seen the idea of adding air pressure in an SBDU machine. A new thread makes it much easier for others to search your idea.

http://www.youtube.com/watch?v=sluei1-IkTw

Keep planning and developing your ideas.

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Wed Jun 26, 2013, 6:01am
Subject: Re: Gaggia Classic PID Temperature Stability
 

Thanks.  My third idea is to plumb the Gaggia (drain and supply) and then get a constant flow of water through the system (supply to boiler to drain) at the correct flow rate (say .1 oz per second).  Let the PID adjust to this (agreed, it should be around 65% power) and then flip the flow from going straight down the drain to flowing through the portafilter.   No (or more likely little) sudden flow rate change (idle to brew) to confuse the PID.

But I admit that I'm getting pretty good espresso using your suggested 4 seconds of steam preheat.  And I see that some people say that some fall off in temperature is beneficial.
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Wed Jun 26, 2013, 11:48am
Subject: Re: Gaggia Classic PID Temperature Stability
 

Your flow rate of 0.1 oz/sec is 6 oz/min and 2.8 gallons/hr if I am doing the math correctly.  Your water and electric bill will suffer if you leave the machine on much.  Now you are talking a plumbed-in SBDU machine.  The PID algorithms should adjust the power well enough but is this practical?  If you just turn it on and allow 30 to 45 minutes for stabilization and then brew and shut down you could limit water and electricity.  You could calculate the additional electricity by getting water temperature incoming, using the flow rate and confirm the amount of water heated and calories/joules needed, and then factor in your utility rates.

You could add a bit about yourself in the introduction thread,

http://coffeegeek.com/forums/members/offtopic/330617?Page=93

and add your equipment, and what you are doing now :)

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Wed Jun 26, 2013, 3:24pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

I would expect that once the system is warmed up without water flow, getting the PID to stabilize to a water flowing condition would only take a couple minutes.  Then turn off the flow right after the shot.  So only a few minutes of  water wasted.
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D4F
Senior Member


Joined: 15 Mar 2012
Posts: 2,015
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Wed Jun 26, 2013, 4:09pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

Sorry, not trying to be negative but understand what you have in mind. How will you control it? Will you stand and operate the flow or do you have electronics and plumbing in mind?  Electronically I hope, to go with the PID, but all on an SBDU...   OTOH, starting on a simple machine is a good way to develop the ideas.

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Wed Jun 26, 2013, 7:15pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

I'm going to use a cheap Gaggia Espresso for hacking on - it will probably end up a mess.  My intention is to use a PID controller for the heater and do all valve control manually.  But I've used Arduinos for other things and it would allow trying more complicated things.     Fuzzy logic,  valve control, flow measurement, multiple temp sensors, etc.  I'm looking for suggestions - if any of this is not going to work, not going to help, be far harder than I think, etc, please let me know.   It's mostly for fun, but I still don't like wasting effort.  Controlling with off the shelf PID and driving the shot with air is minimal effort, so I expect to try that first. And with no OPV, the Espresso should also benefit from the well regulated pressure.
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