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Thread: Gaggia- beyond the pid?

  1. #1
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    Gaggia- beyond the pid?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Id like some feedback on an idea to improve temperature stability during the shot in a gaggia classic. Its an electrical question so Im hoping Mal will chip in (btw, thanks for saving me from wasting my time with some other half baked electrical ideas on the roaster :))

    Im already planning on putting in a pid to stop the wild temperature swings that the thermostat gives but Im wondering about stability during the shot with cold water coming in to the boiler. My recently retired sunbeam em4800 used to turn on its element whenever the pump was running (i think) so Im thinking of doing this on the Gaggia. Kind of.

    skip the physics if you like:
    <physics>A quick calculation on the back of an envelope tells me that given 4.2 joules/gram/degreeC as the specific heat of water and assuming incoming water is 75 degrees cooler than the boiler then I need 315 joules of energy to heat every gram of cold water. so if Im pulling 60 ml in 30s, thats 2grams/second, I would need 630 joules/second </\/physics>
    So I need to heat the boiler at a rate of 630 watts. The sticker on the case says the classic is 1400 watts so I want to half that.

    Im thinking of connecting an old phone charger or similar in parellel with the pump and using it to activate the same SSR that the PID will operate. Im also thinking that 700w will be enough to heat the boiler to brew temp (but not steam) so I could put a high voltage diode in the AC cuircuit that the SSR is switching. This will halve the element power whenever the pid or my little dc supply switches it on. Steaming should be unaffected.

    So, my questions are:
    Will a diode here cause problems for the pump and the PID that cant be fixed by a capacitor?
    Will improving temperature stability improve my shots or is a slight decline in temperature during a shot a good thing?
    Anything else I need to consider?

    Ive read on other forums that a pid will stabilise temperature during a shot but Im sceptical of this claim because the temperature sensor and the element are both outside the boiler while the water is obviously on the inside.* The pid might stabilise the temperature of the outside of the boiler wall but I suspect it wont make much difference to the inside in the time the shot is pulled.

    any suggestions?...
    ::)
    Conan

  2. #2
    enjoy black coffee JamesM's Avatar
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    Re: Gaggia- beyond the pid?

    Actually, while the thermostat isnt IN the water as such, it is buried deep in a threaded well, in the side. I dont think you will get much better than just PIDing.

    Sounds interesting though

  3. #3
    Mal Dimal's Avatar
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    Re: Gaggia- beyond the pid?

    Gday Conan... :)

    I think youre over-complicating matters a bit mate.

    Brew water temperature stability during a shot is already reasonably well covered in a Classic, by virtue of its boiler design and thermal mass of the Group. The most significant benefits from the installation of a PID Controller are:-
    Water temperature can be adjusted very accurately to tailor brew water temperature to the beans being used;
    Doing away with the t/stat(s) means that the operating hysteresis (deadband) is virtually eliminated so doing away with the need for temperature surfing;
    Inter-shot brew water temperature is significantly improved such that there is less time spent waiting for the brew water temperature to stabilise prior to the next shot;
    Intra-shot temperature stability is improved for similar reasons to above.

    When I referred to the Boiler Design as minimising brew water instability, it is down to a characteristic of fluids to stratify vertically with respect to temperature. The water to the Group is taken from the top of the boiler when a shot is pulled, whereas fresh (cold water) enters from the bottom to be immediately heated before rising to the top of the boiler by convection. The upshot of this, is that the brew water entering the Group remains quite temperature stable during the course of a shot.

    If you want better stability, then you need to go via the route of a Pre-Heat Boiler to bring the incoming cold water up to 75-80C for example before it enters the main boiler. Its the only really effective way of achieving this but requires a lot more modification to the basic Classicss design. It has been done before though and the charts profiling the brew water temperature during a shot were very impressive indeed; displaying a falling temperature profile of less than one degree during the course of a 30 second extraction. I guess only you can decide if the amount of work required would be worth it...

    So thats it mate. After the installation and proper setting up of a PID Controller, there is no need for additional fiddling unless you want to go down the Pre-Heat Boiler route. By the way, with proper setting up you should be able to maintain a falling temperature profile of something approaching 1.5C with the PID Controller alone and that is a lot better than many much more expensive espresso machines. 8-)

    Mal.

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    Re: Gaggia- beyond the pid?

    What mal said.

    If you want to look into pre heating, google is your friend. "gaggia pid boiler pre heat"
    will turn up some good threads on coffeegeek and home-barista among others.
    If you want to go the active preheating route, I have a spare thermoblock.

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    Re: Gaggia- beyond the pid?

    Thanks Mal, Thanks Who me,

    Sounds like its not worth the trouble, at least not anytime soon. But it would be much easier than pre heating...

    Heres an interesting article on pre-heating:
    http://www.home-barista.com/espresso...sic-t2794.html
    It shows about 10C temperature drop measured at the puck. or about 5-6C in the first 25 seconds

  6. #6
    Mal Dimal's Avatar
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    Re: Gaggia- beyond the pid?

    Some good information here too from our once resident Physicist Sparky. Its not about the Classic (although Sparky did own a Classic at one time), rather a Faema Family but the modification progress might be interesting for you.... :)

    http://coffeesnobs.com.au/YaBB.pl?num=1130542649/0

    Mal.

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    Re: Gaggia- beyond the pid?

    Thanks for that interesting link Mal
    pre heating would be the way to go instead of the electrical solution. I might just send some copper pipe for a few laps around the outside of the boiler.

    The pid is in now. Cant wait for that morning coffee :D

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    Re: Gaggia- beyond the pid?

    Oh yeah. :D ;D :)
    If anybody is considering putting in a pid, do it.
    It probably cost me about $50 and made my Gaggia 10 times better.

  9. #9
    Mal Dimal's Avatar
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    Re: Gaggia- beyond the pid?

    Quote Originally Posted by 272B2A252A6A2B26362D212A440 link=1305290070/7#7 date=1305496541
    Oh yeah.* *:D ;D :)
    If anybody is considering putting in a pid, do it.
    It probably cost me about $50 and made my Gaggia 10 times better.
    I agree mate.... [smiley=thumbsup.gif]

    Probably the best thing that any owner of similar machines can do to improve the quality and consistency in the cup. Especially these days with controllers being so cheap.... 8-)

    Mal.

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    Quote Originally Posted by Dimal View Post
    I agree mate.... [smiley=thumbsup.gif]

    Probably the best thing that any owner of similar machines can do to improve the quality and consistency in the cup. Especially these days with controllers being so cheap.... 8-)

    Mal.
    Thanks to your words in this thread it pushed me to do just this, thanks.

    Got a 9yr old classic for $100 a bit over a week ago, great condition superficially. Pulled it to bits full clean/ manual de scale, replaced all seals and changed out the old leaking Invensys pump for a newer ulka out of my now non functioning Coffee deluxe.

    Grabbed a sestos PID and all the bits, finished it all last night.
    What a joy this mornings coffee making was! Holds the temp pretty much spot on all the time or within 0.3 degree. No waiting, guessing, surfing and flushing. After a year of such stuffing about the difference is an absolute pleasure / relaxing. I can actually notice the taste difference changing the setting 1 degree.

    OH yeah and how good it is having a 3 way solenoid!

    I let the machine heat up for half hour then ran the auto tune. Took about 10mins but I was not happy how it was constantly overshooting and sitting 1 degree above its mark.
    I reset and ran AT again and straight away ran about 60 ml of water through then left it. After it was done it stayed pretty much bang on target most of the time, very happy with the temp drop during a double shot of only around 2 degrees. K type thermocouple is buried as deep as possible in old thermostat hole.
    Have ordered RTD from Auber to compare, just can't stop playing...
    Getting K3P in a few days for combined bday gift, can't wait to taste difference from my Porlex hand grinder.

    Anyone reading up and considering installing a PID, just do it! You won't regret it.
    Goes without saying great care should be taken with electrical work.

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    Quote Originally Posted by conan.obrien View Post
    Oh yeah. ;D
    If anybody is considering putting in a pid, do it.
    It probably cost me about $50 and made my Gaggia 10 times better.
    How can this be done for $50?
    The kits on ebay are $200?
    <Mitchell

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    Quote Originally Posted by sawpitcreek View Post
    How can this be done for $50?
    The kits on ebay are $200?
    <Mitchell
    If you are DIY handy, and electrical savy ( as you must be to even consider a kit install).. then dont buy a kit, just find a PID & SSR ( ebay..$25) and use a little common sense. .. Its not too difficult.

  13. #13
    Senior Member deegee's Avatar
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    Quote Originally Posted by sawpitcreek View Post
    How can this be done for $50?
    The kits on ebay are $200?
    <Mitchell
    Not sure where you're looking. I just did a search on their site for "pid controller" , and it came up with heaps - all under $50

    There are PID's for as little as $12 - 13 SSR's for $3 - 4 and thermocouples from $2 to $20

    Then there are lots of kits with all three items, ranging from just over $20 to $50.

    Everything under $50 is from China or Hong Kong, and would no doubt take weeks to arrive, but they are available.

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    Yep i got the Sestos D1S-VR-220 + SSR + K type thermocouple for $38.50 delivered from Hong Kong and only took 10 days which was pretty good.

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    Re: Gaggia- beyond the pid?

    Also lots on amazon.

    For anyone feeling more adventurous, check out www.ospid.com for a fully open source arduino compatable pid controller. I use one on my popper.

    Quote Originally Posted by conan.obrien View Post
    I might just send some copper pipe for a few laps around the outside of the boiler.
    This will still cool the boiler when you add more water if it is in physical contact (as the boiler is still your heat source). With a longer delay though.

    You can buy special heating unit to wrap pipe. Maybe something like that could be adapted?

  16. #16
    Probably drunk on coffee bodyboardingbum's Avatar
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    Researching, plotting, and formulating a plant to see if a similar eBay DIY PID can be put together cheaply for a Gaggia Baby Dose.
    From my research, it appears it has almost identical parts to the newer Classic - only a slightly smaller boiler.

    Anyone care to throw in some though, input, and perhaps parts they have successfully used in their Gaggia?
    Already does "pre-infusion" and such OOTB, would this be retained? I know some of the PID Kits for the classic do this.



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