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Thread: Silvia Temp profile

  1. #1
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    Silvia Temp profile

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi all
    I thought I would let you know my experience so far with the secondhand 2 or 3 year old Silvia/Rocky combo I puchased from the hardware for sale section.
    I must thank my brother for picking it up for me and delivering it to SA also the work he has done with the temp controller .
    The initial temp variation was 21 degrees C from a low of 81 to a high of 102 as measured with a probe on top of the boiler. This certainly was just not going to cut it.
    So Lindsay and I thank you very much decided to make a Temp controller using a Microprocessor that is readly available for all sorts of projects, and writing the appropriate software.
    I now have static temp held to 1 degree of the set point and also adjustable.
    The temp drop during a shot is about 4-6 degrees as measure on top of the boiler.
    The coffee is tasting great.
    It is a pleasure to be able to go to Miss Silvia now knowing she is ready to go.

    I now just have to get the roasting and blending down pat

    Regards All

    Trevor ;D



  2. #2
    Senior Member robusto's Avatar
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    Re: Silvia Temp profile

    Thats very interesting Trevor, always interested in Silvia mods. Certainly a huge improvement in the temperature stability youve achieved.

    Would you be kind enough to post details of the microprocessor and other materials used, with costs.

    Thanks in anticipation,
    Robusto


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    Re: Silvia Temp profile

    For reference attached is a photo of a second one hooked up to my Domobar ;)


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    Re: Silvia Temp profile

    The basic materials used are;

    Picaxe 18X microcontroller (see picaxe.co.uk for more info)
    Digital temp sensor
    Blank circuit board & etching acid
    16 x 2 LCD display
    30A relay
    12V transformer with remote plug (to enable plug cut off & connected to Silvias power switch)
    qty resistors & capacitors, transistor, diode, voltage regulator, wire etc..
    small case to house it all in.
    Hours to design basic circuit, breadboard test, improve, re-test, write basic program, improve program & test, design circuit board & etch.
    Some more hours to do a final assemble & admire - then finally some more hours to drink liquid the gold *;D ;D :o

    All up the cost was roughly $100 or maybe a little more, With completed PID projects Ive seen (including relay & power) running around $250-300, its a reasonable saving.

    The best thing is it works a treat.

    Im not sure if theres interest, but for enough $ to cover the cost of etching acid, blank circuit board & some of my time (running around etc) I could probably put together a "kit" with a pre-programmed cpu, etched circuit board, all other components required & instructions on assembling. *

  5. #5
    Senior Member robusto's Avatar
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    Re: Silvia Temp profile

    Thanks very much for that information, LW. I think the controller is a just a tad more complicated than those Dick Smith project kits! *
    Maybe you should go into business mass producing them. *What do other CSs think?

    regards,
    Robusto

  6. #6
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    Re: Silvia Temp profile

    Whooo-eeeee!

    Reminds me of the control panel on the new La Marzoccos (GB-5). Looks cool.

    My question is, how does it work? Does it use fuzzy logic like a PID or is it essentially a glorofied tstat like on the brewtus?

    My Silvia goes from about 92 to 112 or so with my boiler-mounted thermometer, so its nice to see that we have been getting the same results. The only thing is that Im not sure that theres a linear temp drop to the cup. There were some charts on CG showing Silvia to have 2-3C variation within the shot, whereas a gaggia classic fluctuated like 9-10C. Kaanage, master of all things temp-geeky, explained this with reference to the group head. On the classic, the boiler is directly on top of the group. With Silvia, the group is slightly remote, so it evens the temperature fluctuation out, kind of like a really crappy actively heated group ... I guess. What do yall think?

    ... but I return to the fundamental premise; does it taste better? If so, good!

    Chris (2muchcoffeeman) and I are actually looking a PIDing our silvias at the end of the year. Im sure that both of us would be interested in kits!

    One other thing, though. I reckon steaming on a silvia would be MUCH easier if we could keep the boiler at a constant temp. Can you use your controller to control steam mode, too?

    Great work!

    Luca

  7. #7
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    Re: Silvia Temp profile

    Just to clarify, PID and fuzzy logic are different things. Its just that _some_ commercial PID controllers use fuzzy logic to automatically set the P, I and D parameters for you, rather than you setting them manually. Once these controllers have "auto-tuned" they operate in exactly the same way as a manually tuned PID controller.

  8. #8
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    Re: Silvia Temp profile

    I didnt use a PID algorithim when I programmed it, I wanted to keep it simple and cheap (PID would also require a solid state relay adding more $$)

    when I used it as a straight electronic thermostat (I believe the brewtus operates this way showing set temp rather than actual) it reduced the variation from 21 degrees to six. Using trial and error I programed heat & wait cycles as it approaches the set temp based on the difference. The end result is on both the silvia and domobar it ramps up to temp slowly to avoid overshooting and once warm holds the highs & lows to a typical 1 degree variation. It still overshoots a little on initial warmup and immediately after pulling a shot, but it settles down quickly.

    On the silvia it reduced the whole heating cycle from 12-13 minutes, 30 or so seconds heat and 12 or so minutes cooling to around 104 seconds, 3-4 seconds heat & 100 or so seconds of cooling.

    I see no reason why it couldnt control steam also, the easiest way would be to add a "steam" button to the controller and some additional programming to raise the set temp, bypassing the original steam button completely. I havent tried it at higher temps, it might not hold the variation as tight maybe a 2-3 degree variation - still better than the original mechanical steam thermostat though Im sure.

    In terms of in shot temp variation, my understanding is the mass of metal and overall design helps reduce dropping of temp during a shot. I can see that a large mass around the grouphead would also help even the temperature of the water as it flows through it. A large mass of brass wont fluctuate quickly and will act like a thermoblock of sorts (My domobar has an E61 grouphead which gets b#&dy hot).

    A replacement thermostat cant change the thermal mass of your machine but at least it can help keep the initial temp of the boiler water consistent before pulling a shot - no more temp surfing.

  9. #9
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    Re: Silvia Temp profile

    Oh - I forgot to mention,

    Speaking purely for myself, it hasnt turned me into a world champion barista overnight with the ability to pull god shots everytime ... BUT

    I havent really pulled a bad shot since either, just reasonably consistent nice shots. Before I would pull a "doh" sour tasting shot in a hurry, smack my forehead with my palm and remember to wait for the heat light to go out, count my guessed amount of time and try again.....

    I hated temp surfing, it was motivation enough to build this thing!

  10. #10
    Mal Dimal's Avatar
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    Re: Silvia Temp profile

    Hi All,

    Sounds like a great project for the electronically inclined coffee geeks and snobs out there. I think for all the rest though, using a commercial micro PID Controller with, or without Fuzzy Logic is still a more straight forward option, if a little more expensive.

    Quite acceptable Controllers can be had for less than $140 delivered, a suitable SSR for less than $20 and a short length of thermocouple wire for $5-6. Probably wont get the same level of satisfaction as someone who has manufactured the whole kit and caboodle from scratch, but there will be a lot of satisfaction derived while sipping some excellent espressos 8-).

    And Luca.... you can obtain PID units with more than one control channel so by using your existing Steam Switch, the PID unit can be toggled between two Setpoints, one for Brewing and one for Steaming. These units wont be at the cheaper end of the scale but still less than $200.

    Technology, dont you just love it :)

    Cheers,
    Mal.

  11. #11
    Senior Member robusto's Avatar
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    Re: Silvia Temp profile

    PID controllers are advertised regularly on *bay, but a word of caution. * Many are unsuitable for coffee machine application. *On the surface they seem ok. But when you get down to the specifications -- which arent always given -- their shortcoming becomes evident.

    More commonly, the voltage input may not be suitable for Australia. *But even if it is, the type of relay specified isnt suitable. Some relays are not solid state. Id imagine they would fail because of the constant swiching. *Or, they may not be of the right amperage-- usually too low.

    When All Else Fails....read the specs. And try to get more information from the manufacturers website. Though I confess, sometimes its impossible to tell what brand is being sold.

    Incidently....I did buy a central heating/air conditioning Honeywell thermostat from the USA on *bay. *And blow me down.... it has a PID-style self learning *function. So if you set the timer for 20 degrees at 6 am, *over a few days it will learn by trial and error how long in advance to *switch on the heater/air conditioner. *And similar for switch off at night so theres no overshot.

    -Robusto

  12. #12
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    Re: Silvia Temp profile

    Youre spot on Mal,

    PID controllers have R&D and quality designers behind the product. Most PIDs are made to operate in harsh factory style environments.
    IMHO they are a bit of overkill for a home espresso machine but theres not a lot of choices between a standard mechanical thermostat and a full PID. With a complete PID setup for around $170 you cant go wrong though. *Just because I was prepared to spend the time designing and making this one doesnt mean its for everyone.

    I have to admit though, everytime I walk past my machine I admire my handywork *8-)... the wife is sick of me bragging about it ;D ;D


  13. #13
    Mal Dimal's Avatar
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    Re: Silvia Temp profile

    Hi LW,

    More kudos to you, in my view [smiley=thumbsup.gif]. Great way to spend ones time I think and deserved of all the bragging rights you want to pursue. I used to build a lot of gadgets along these lines years ago.... even built my own computer from scratch way back when....

    My lovely wife never complained about my endless stream of projects though, or the clutter that used to accumulate.... when it all became too much Id just come home from work one day and find it all stacked very, very neatly in front of the store-room door in the garage :P. A pretty good hint that it was time to clean up a bit ;).

    We blokes have got to have our stuff to tinker with, its even a scientifically proven fact now ;D,

    Mal.

  14. #14
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    Re: Silvia Temp profile

    Behmor Brazen - $249 - Free Freight
    Yeah, I have to admin Im lucky that way too.. Im constantly going from some tinkering type project to another, helps take my mind away from work and I figure its better than watching the tv.

    My wife on occaision complains about the time I spend in either in the Garage or Study - but completely understood and accepted my need for both ;)



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