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Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
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jonr
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Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Fri Jun 28, 2013, 1:08pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

It looks like the the only thing making an up-the-wand air driven shot non-trivial to test is the copper tube in the boiler that forces the flow to come from the top of the boiler.  That needs to be removed so that water flows out as air comes in.
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jonr
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Location: Americas
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Posted Sat Jun 29, 2013, 8:05am
Subject: Re: Gaggia Classic PID Temperature Stability
 

From watching a pressure gauge, I can see that an air driven shot will have a faster pressure ramp up than the pump.   Ie, 0->9 bars almost immediately instead of over 10 seconds or so.   Even faster than a rotary pump.   I don't know if this is good or bad - maybe a slow ramp up creates some pre-infusion.  I suppose than a restriction in the air line could be added to slow it back down.
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D4F
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Joined: 15 Mar 2012
Posts: 2,021
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Sat Jun 29, 2013, 9:11am
Subject: Re: Gaggia Classic PID Temperature Stability
 

D4F Said:

Jon, an interesting post, welcome to CG.  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.

Posted June 25, 2013 link

More interesting ideas.  I have some thoughts and comments and would be happy to share them on a new thread.  You are posting on a thread with 30 pages most about PID and your ideas deserve a new topic, new thread not just post buried in these pages.  You might even find others with ideas if you start with a title like Compressed Air Espresso or Air Driven SBDU. Choose the new topic carefully as that makes your concept more easily searchable.  I am again asking you not to hijack this thread and trying to show you that there is benefit to you of starting another.  

Thanks :)

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
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Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Sat Jun 29, 2013, 6:16pm
Subject: Re: Gaggia Classic PID Temperature Stability
 

OK, done.
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brianl
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Joined: 1 Dec 2012
Posts: 490
Location: Chicago IL
Expertise: I love coffee

Espresso: Quick Mill Vetrano DB
Grinder: HG One, OE Lido 2, Baratza...
Drip: Chemex/V60
Roaster: Behmor 1600
Posted Mon Jul 15, 2013, 10:52am
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

Hey,

With that 1/16 PID. I want to put it in a project box now but i'm not particularly fond of the ones on aubers web site, especially for $30 shipped. Do you have any other compact project boxes that you've used before or are familiar with?

thanks.
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D4F
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Joined: 15 Mar 2012
Posts: 2,021
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Mon Jul 15, 2013, 7:30pm
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

You can search project boxes at various electronic stores or on the internet, but this is about the size you need. I left mine out, but almost got this one.

Click Here (www.radioshack.com)

Unfortunately no size is perfect and will either be too large or require some fitting.  The posts to hold the screws for the bottom are often the difficult part.  You may need to use a Dremel and flatten the inner aspect of the post to widen that dimension.  Of course you have to cut the end between the posts to make your square hole.  Cut down along the posts and break off the bottom 3rd side.  I have used similar for other projects and they are fairly easy to work with.  I find that a slight under cut and then sand/file and fit works fine.  Of course a hole in the back for the wires to enter.  When I switched PIDs, the equivalent to moving wires through the box, I simply remover a wire and labeled it with a small piece of tape and rolled it up to go through the hole and then reconnected everything. I did not want to think through each connection again.

I will assume that you kept the rubber collar for the PID as it may help the fit.

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
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Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Thu Jul 18, 2013, 8:32am
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

I had a chance to reread this entire topic (lots of good info!).  My conclusion (mirroring what others have said) is that the Classic would benefit from a controller that uses PID for steady state boiler temperature control but switches to open loop control for the brew.  Ie, when you are ready to brew, the controller would turn on the heater and then a few seconds later, you would switch the pump on.  During the brew, the heater would be controlled to some % of full power (around 2/3, should vary based on incoming water temp and ambient temp and should vary throughout the shot).  An Arduino would be a good choice to do this PID + table lookup control.  There are also Arduinos smaller than your thumb, so mounting is easier.

With such a controller (or manual temp surfing equivalents), I see no reason that espresso from a Classic isn't as good as from multi thousand dollar machines (and better than my $1500 HE machine where brew temp is sensitive to lots of variables).
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D4F
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Joined: 15 Mar 2012
Posts: 2,021
Location: USA
Expertise: I like coffee

Espresso: Gaggia Classic PID
Grinder: Baratza Forte-AP
Posted Fri Aug 2, 2013, 9:16am
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

Using the Classic as usual with brew heat, when I finish a pull the PID shows a high temperature since heat was added in the brew.  The idea is to match heat calories to cool water calories and stop the intrashot drop.  It finally occurred to me that the temperature took fairly long to fall back to set value, but you do not have to wait for that.  The extra heat is about the right amount to take the place of the pre-shot steam switch.

At the end of the pull, I switched off the machine and waited a brief time and the temperature fell quickly toward normal.  Of course the PID had been also stabilizing against rapid fall of temperature, it is active on either side of set.  You can get an idea of the heat match that you set up if you turn off the machine for several seconds and let the water mix without the PID trying to stabilize the fall from “undershoot.”  You can also cool the machine much more quickly as the water will bring the temperature down and you can see, and use that with the PID not adding heat.  In practice, you may have not added a full amount of heat calories to compensate the cool water as it is layered and not well mixed and the PID keeps pumping in heat.  A reading after several seconds may give you a reading a few degrees below set.

While this may not add much to the actual use of the alarm function to add heat with brew, it does help with the understanding of the process.  Once again the PID is actually “stabilizing the sensor” temperature.  Similar to shortly after you turn on the machine and you see the set value reached and it looks stable.  Turn it off a few seconds and see if the temperature falls much.  Of course, until the machine temperature is stable.

 
D4F also at
http://www.gaggiausersgroup.com/
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jonr
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Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Fri Aug 2, 2013, 12:20pm
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

A couple of general comments.  PID doesn't do very well with rapidly changing conditions like water flow starting and stopping.  The result is typically undershoot and overshoot.  Always keep in mind that the temperature sensor may not be reading the actual temperature of the water.  For example, if you measure near the heating coils, you may see wide swings in temperature when the actual water temperature is pretty stable (or lagging the sensor).

My low mass PT1000 RTD arrived today so I can proceed with an Arduino controlled system (with PID during non brew, open loop control just prior to and during brew).
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jonr
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Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Mon Aug 5, 2013, 12:32pm
Subject: Re: Gaggia Classic SBDU Preheat PID Temperature Recovery and Stability, Steam
 

I got computer control of boiler temp working today.  I'll start another topic about it.
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