# Gaggia Classic with volumetric control



## MrShades (Jul 29, 2009)

Not sure if this is of interest to anyone else, but a while ago I looked at how easy it was to fit an automatic shot timer to the Classic (and posted a quick HowTo on here as it was pretty simple).

Now, whilst shot timing is interesting and can be useful/fun, I've been thinking since then whether it'd be possible to do something similar but volumetrically measuring the water being pumped into the boiler (and hence into the portafilter, the coffee and ultimately most of it ending up in the cup).

Quite a lot of thinking - followed by some research, some light plumbing, further purchasing, a bit of wiring and messing around and I've got it working reasonably well now.

Here's a few videos of it in testing.

The first pour is close to a choker, the next is a lighter dose of coffee but at the same grind setting, and just for fun the last one is with an empty basket.

I didn't drink any of them - it was just for fun... and before anyone asks, the 350 value is just a relative number and doesn't directly correspond to any particular volume (ie it's not 3.50 fl oz or anything)

I'm tempted to develop this further and possibly produce it as a kit - if there's any interest in me doing so?

Anyway - have a look:


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## Rhys (Dec 21, 2014)

That's excellent! Along with a PID and pre-infuse, you could be onto a winner!


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## Khashy (Mar 10, 2015)

+1 to the intersted people's group.

Add in a pressure profiling kit and I will never swap my Gaggia Classic for anything.


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## MSM (Mar 12, 2015)

I think it's great!









I would be interested in a kit - depending on price the final price.


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## timmyjj21 (May 10, 2015)

Looks sweet! I have been pondering the same thing, but it looks like you are several stages ahead of me!

I'm certainly interested.

Would it be possible to still have an integrated shot timer with the volumetric setup that stopped when the dose was reached? I feel that showing the time taken would be more informative than reaching an arbitrary preset number.


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## Jollybean (May 19, 2013)

Always interested in new ways to pimp my Classic. Put me on the list


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## Riz (Oct 19, 2015)

Really interested in this.


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## Asgross (Jun 14, 2015)

Looks really interesting


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## destiny (Jun 4, 2015)

That's quite something! How are you measuring the output and where? How about changing volumetric to shot ratio/weight control...


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## MrShades (Jul 29, 2009)

timmyjj21 said:


> Looks sweet! I have been pondering the same thing, but it looks like you are several stages ahead of me!
> 
> I'm certainly interested.
> 
> Would it be possible to still have an integrated shot timer with the volumetric setup that stopped when the dose was reached? I feel that showing the time taken would be more informative than reaching an arbitrary preset number.


I've pondered this one - and I can't come up with a way to do it at the moment. The 1/16DIN digital timers typically expect to be "controlling" (ie you set a time and the timer turns a relay on/off at the pre-set times). I can't find any sort of 240V powered device that would use a 240V signal to start/stop a 'stopwatch' - which is what would be required. The only way to stop the ones that I know of, with a 240V signal, is to kill the 240V power to them - and then you can't see the time!

If anyone can find a 240V timing unit, that will start and stop based on a 240V signal - then it may be possible, as I agree it would be useful.


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## MrShades (Jul 29, 2009)

destiny said:


> That's quite something! How are you measuring the output and where? How about changing volumetric to shot ratio/weight control...


I'm not measuring the output - I'm measuring the input from the tank to the pump, and rerouting the output from the OPV to the pump input also. Hence there's only one pipe into the tank now, and a small digital flow-meter is measuring what's being drawn from the tank. This is why the pump "stalls" in use, as the OPV pressure is going back to the pump and not back to the tank (hence it's a semi-closed system and the pump can't just pump constantly, drawing from the tank and with the OPV dumping back into the tank). Simples! (However, I'm not too sure how the pump will get on in the longer term, but it doesn't seem to mind!)

Weight/mass is something I've also thought of, through the use of a load-cell in the drip tray. Engineering something within the drip-tray would be largest challenge, rather than the electronics to control it. However, to do it properly would require more than a simple "dumb" off-the-shelf module (like this 1/16DIN timer unti) and it'd need an Arduino and some careful programming to get something working well. Unfortunately I just don't have the time to get that deep into it at the moment :-(


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## destiny (Jun 4, 2015)

MrShades said:


> I've pondered this one - and I can't come up with a way to do it at the moment. The 1/16DIN digital timers typically expect to be "controlling" (ie you set a time and the timer turns a relay on/off at the pre-set times). I can't find any sort of 240V powered device that would use a 240V signal to start/stop a 'stopwatch' - which is what would be required. The only way to stop the ones that I know of, with a 240V signal, is to kill the 240V power to them - and then you can't see the time!
> 
> If anyone can find a 240V timing unit, that will start and stop based on a 240V signal - then it may be possible, as I agree it would be useful.


How about a 240v relay thats just a switchover and is connected to a dc power?


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## coffeechap (Apr 5, 2012)

You are the king of the classic


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## MrShades (Jul 29, 2009)

coffeechap said:


> You are the king of the classic


Thanks Dave - I try... though I've yet to try and get every mod on a single machine! Space is at a premium in a modded Classic, but you already know the answer to that one ;-)


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## MrShades (Jul 29, 2009)

destiny said:


> How about a 240v relay thats just a switchover and is connected to a dc power?


You're going to have to explain that one a little more... sorry!


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## MrShades (Jul 29, 2009)

For the "potentially interested" folks ( @Khashy @MSM @timmyjj21 @Jollybean @Riz @Asgross @destiny )...

Having looked at the parts and effort required to pull this together, I think I could do a simple kit for £30 + postage. However, this wouldn't include my aluminium 1/16DIN case - which would be an additional £20 (including post, for case or the whole kit). So - £50 delivered in total.

Ideally the timer unit needs to be accessible, as you have to hit the "Reset" button on the bottom right (to zero the counter) between pulling shots (if you don't, then the brew switch does virtually nothing).

Alternatively, rather than pressing the button on the timer it's also possible to fit an external push-button to provide the "Reset" - though this would also need to be mounted somewhere - and ideally I'd like this to be 100% reversible (and drilling holes in cases for buttons can't be undone!).

Final kit would include new silicone hosing, with all connections and flow-meters mounted within it - and then you simply repalce your existing pump-to-tank silicone hose with the new one, and add your current OPV output pipe to it - and then cable up the timer (with about 7 or 8 wires going from the timer into the Classic's case). Much easier to fit than a PID.

So - given the above, should I set the wheels in motion...?


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## timmyjj21 (May 10, 2015)

It's a go for me!

I'll probably go the basic pack and see if I can use my existing aluminium square tube housing. I assume the unit is the same standard size as the Rex PID?


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## Asgross (Jun 14, 2015)

Mr shades please put me down for the kit inc case

Thanks


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## MrShades (Jul 29, 2009)

timmyjj21 said:


> It's a go for me!
> 
> I'll probably go the basic pack and see if I can use my existing aluminium square tube housing. I assume the unit is the same standard size as the Rex PID?


Yes, standard 1/16DIN - 45mmx45mmx (something) - though I don't think it's as long as a Rex C100 - so if you already have a case for one (or tube for one) then it'll fit.


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## MrShades (Jul 29, 2009)

I'll proceed with 5 initial kits and see what happens with them and whether people enjoy them and value them - or find them a PITA and remove them!

So - it'll take me a while to source the components (many are from China) and will report back once an initial batch are available. Gives me some time to write the instruction manual I guess!


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## Riz (Oct 19, 2015)

Would this work together with the Pid?


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## hotmetal (Oct 31, 2013)

Impressive work Mr Shades. I'm always intrigued by the ingenuity and focus of some of you guys in the name of better coffee. Ultimate Classics, mythical grinders, clever software apps/scripts...


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## destiny (Jun 4, 2015)

Ill pass for now. Sorry. On the subject of the relay though... the timer should work on a trigger (rising or falling edge) so what you need is change of voltage level. Instead of trying to get a timer working with 240v add a relay that switches with 240v on the coil but have the switching connection wired for dc. So when the gaggia's button is pressed it will trigger the coil on the relay, this will switch and i.e. close the circuit which will go to +vdc and will than be triggering the timer. Is that better?


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## MrShades (Jul 29, 2009)

Riz said:


> Would this work together with the Pid?


Yes, of course it will.


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## MrShades (Jul 29, 2009)

destiny said:


> Ill pass for now. Sorry. On the subject of the relay though... the timer should work on a trigger (rising or falling edge) so what you need is change of voltage level. Instead of trying to get a timer working with 240v add a relay that switches with 240v on the coil but have the switching connection wired for dc. So when the gaggia's button is pressed it will trigger the coil on the relay, this will switch and i.e. close the circuit which will go to +vdc and will than be triggering the timer. Is that better?


The problem is finding a timer that works like that. Typically they control the time that something operates for, rather than reacting to an external input.


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## Khashy (Mar 10, 2015)

Hi, still in the very much interested camp.

Just wondering how the pump start/stops which i presume will have an affect on the water pressure acting on the coffee impact the extraction and ultimately the taste? Do you find a difference in the cup between a normal PID'd classic and one with the volumetric control?

thanks.


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## MrShades (Jul 29, 2009)

Khashy said:


> Hi, still in the very much interested camp.
> 
> Just wondering how the pump start/stops which i presume will have an affect on the water pressure acting on the coffee impact the extraction and ultimately the taste? Do you find a difference in the cup between a normal PID'd classic and one with the volumetric control?
> 
> thanks.


It's more a case of the pump stalling rather than starting and stopping.

The output of the OPV is rerouted to the input of the pump rather than back into the tank, so there is no constant pumping out of the tank and back into it via the OPV - it's a closed loop now.

To be honest I've not really used the volumetric machine must - so not easy to compare - but in theory this is purely a control mod and will make no difference in the cup at all.

Still waiting for a few key parts from China, but initial kits are coming together slowly


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## timmyjj21 (May 10, 2015)

Hey, just wondering how things were going with development?

I had a random though about integrating with your shot timer mod... Most of the timers have a 'pause' function. If you could make the flow counter activate the timers pause function when it shuts off the pump, this would stop the time counting, but still have the time displayed. The timer need not be plugged in and controlling anything. I guess this depends on the outputs of the counter relay you are using but may be possible?


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## MrShades (Jul 29, 2009)

I'm just about there - but have been pondering on the question of inter-shot reset for a while.

Currently you have to press the RESET button on the front of the counter between shots.

I'm thinking of supplying a hard momentary push button that could be mounted on the counter case or even on the Gaggia case - so you can press a small stainless push button in between shots.

I've also been looking at possibly using a non-regenerating mono stable multivibrator to achieve the same thing automatically but my electronics skills and the extra complexity (and cost) are causing me some issues at the moment!


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## smorgo (Nov 22, 2015)

I've been contemplating a major reworking of the Classic recently, by switching all of the control signals to low voltage and replacing the switch panel with something more intelligent. Just SSR's to integrate with the necessary mains switching, though getting another one or two SSR's in there would be a squeeze. I figure that a half-decent microcontroller could take on the the role of PID and shot timer. Using Bluetooth or WiFi, we could also do away with any programming controls to, by delegating those to a phone or web interface. Would be (another) fun project.


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## Khashy (Mar 10, 2015)

@MrShades, did you have any joy with this in the end?


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## MrShades (Jul 29, 2009)

Well, I've got all of the parts - but have never managed to get round to putting it all together as a "kit". Also, I've never managed to get around the small issue of needing to reset the counter - either by pressing the RESET button on the unit or via a small momentary push-switch (that I also have parts for).

If you're interested in trying it, then I can work out a price for the kit - and put some simple instructions together quite quickly (it's not difficult to install). Let me know.


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