Gaggia Users Group

Hardware Discussions => Gaggias with Aluminum/Brass Boilers => Modifications to your Gaggia => Topic started by: The Big L on December 05, 2017, 08:29:36 AM

Title: Mods planning for Gaggia Classic circa 2007
Post by: The Big L on December 05, 2017, 08:29:36 AM
One use case for this that I can think of is that I would like to set the OPV to around 9 bar to make espressos using a non pressurised portafilter but if someone who does not have any interest in making an espresso and the 'work' that goes with it such as grinding and tamping etc. would like to use an ESE Pod which I believe requires a higher pressure such as 15bar, it would be nice to be able to adjust the pressure easily.

That's about the only plausible use case I could come up with.  Unless you already have a roommate or a family member/etc. who prefers ESE pods, then it seems like an awful lot of work for something that is not likely to be used.  BUT, you seem enthusiastic about it and if modding for the sake of modding is your thing, go for it!

I have a dimmer installed on my pump.  IMO it's not a reliable way to control the pressure.  Sure, a 'low' setting on the dimmer results in a low pressure, but the response is not as smooth and predictable as one would like.  Maybe with careful selection of a dimmer you could get better results.  Since you're studying electronic engineering, maybe you could design a dimmer circuit to meet your specifications!

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I was wondering while looking at other peoples setups why nobody installs their PID inside the case with the controls on the outside? Is this just due to the lack of available space in the Gaggia Classic case?

Just speculation, but an Auber (and similar units) are probably too big to fit comfortably inside the Classic case.  AFAIK they're also not made specifically for the Classic, so they're designed somewhat generically.  I bet a custom PID could be made to fit inside the case if you really wanted to, along with a tether to an external display/button module.  However, it gets pretty hot inside the case, so you'd want to make sure that your components could handle that.

I chose a different approach for my PID.  I have a Rasperry Pi running the PID (and pump on/off control).  The Pi and associated circuitry sit behind my Classic, out of sight.  It's running a web server, so I wrote a custom interface (web page) to control my coffee.  I just use my iPhone to control my brewing process through its browser.
Title: Re: Re: Hello from Ireland
Post by: RobertMcConnell on December 05, 2017, 02:05:20 PM
I am a bit conflicted about whether or not I should add the external control to adjust pressure as I could needlessly damage the machine for not much potential gain, so for now I will put it on hold but go ahead with the pressure gauge and adjustable OPV.

Thank you for telling me about the lack of reliability with the dimmer switch mod, I had a read through the long thread (http://www.gaggiausersgroup.com/index.php/topic,193.0.html) where you and others talked about your experiences with the mod. For now I am going to focus on getting the basics right before I start messing around with pressure profiling!

Everything you have said about the PID makes a lot of sense, going with a more DIY custom built PID might work better size wise but cooling could be a problem. There is a lot for me to think about but you have given me a good start, thank you for your help.

Your setup sounds great too! Do you have pictures of it anywhere?
Title: Re: Re: Hello from Ireland
Post by: The Big L on December 05, 2017, 08:25:33 PM
Thank you for telling me about the lack of reliability with the dimmer switch mod, I had a read through the long thread (http://www.gaggiausersgroup.com/index.php/topic,193.0.html) where you and others talked about your experiences with the mod. For now I am going to focus on getting the basics right before I start messing around with pressure profiling!

I really like using my dimmer.  I use it with every pull to slowly ramp up the pressure -- a sort of pre-infusion.  But yeah, after using it for a few years I don't think it's the best tool to achieve a particular brew pressure with much precision.

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Your setup sounds great too! Do you have pictures of it anywhere?

Thanks!  Mine's actually not very pretty at the moment -- certainly not photo-worthy.  :D  Since it hides behind the machine in the corner, it's not something I think much about.  I have a breakout cable from my Pi to a breadboard.  One day I'll get around to stacking a Pi HAT prototype board on top of the Pi and finding/building a nice case for it.  Ideally it would attach magnetically to the back of the Classic and remain totally out of sight.
Title: Re: Re: Hello from Ireland
Post by: RobertMcConnell on December 07, 2017, 03:36:27 AM
Am I correct in thinking that the dimmer switch reduces the pressure in the system by limiting the power going to the pump? Is there a reason why this is the method used for pressure profiling and not something like an adjustable OPV? To my understanding the OPV sets the maximum pressure that can be in the system but if it say started at 3 bar and then was slowly adjusted and ramped up to 9 bar would this not be a form of pressure control?


Thanks!  Mine's actually not very pretty at the moment -- certainly not photo-worthy.  :D  Since it hides behind the machine in the corner, it's not something I think much about.  I have a breakout cable from my Pi to a breadboard.  One day I'll get around to stacking a Pi HAT prototype board on top of the Pi and finding/building a nice case for it.  Ideally it would attach magnetically to the back of the Classic and remain totally out of sight.

Ah I see, sounds like a great project. I am considering doing something similar myself in the future but at the moment I have a long list of mods I want to do!
Title: Re: Re: Hello from Ireland
Post by: RobertMcConnell on December 08, 2017, 04:42:16 AM
I found this YouTube video (https://www.youtube.com/watch?v=zU2Rzy_m5bw) of a setup with a 'flow regulator' but I can't find any more information about how it works.

A turn dial on the side of the Classic beside the steam knob is used to adjust the 'flow' (pressure?). It would be great to get more information on this if anyone has an idea of what is happening on the inside. It seems like a neat way to profile and looks like it works quite well.
Title: Mods planning for Gaggia Classic circa 2007
Post by: JojoS on December 08, 2017, 06:39:50 AM
Looks like some kind of dimmer or electronic voltage regulator that is attached to the pump. From my research on this mod, it is reported that it works better on Invensys pump than Ulka pump. Check what you have.
Title: Re: Mods planning for Gaggia Classic circa 2007
Post by: The Big L on December 08, 2017, 10:37:39 AM
My dimmer switch works basically like that -- and I assume the same is true for most or all of those who have done the dimmer mod.  The main issue I've encountered is a non-linear response from the pump when turning the dimmer dial.  As JojoS says, it may be that the Ulka pump just does not work as well with less power.

I just reviewed the thread from 2013/2014 where I described my experience with the rotary dimmer.  At one point I was worried that I was damaging my pump.  I can't remember or explain the apparent change in the sound of the pump that I described in that thread, but I've been using it daily for almost 4 years and everything is still fine.

Thinking back to how I tested the dimmer, I was using a pressure gauge with no flow.  That could explain my difficulty trying to map a certain setting on the dimmer dial with a particular pressure.  The pressure/flow response of the pump in a closed system is probably not the same as when pulling a shot.  I've always thought an inline pressure gauge would be a neat mod, and if I ever do it I'll have a better idea how the dimmer works to affect pressure.