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The Ultimate Expresso Machine DIY

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  • The Ultimate Expresso Machine DIY

    Hi CS,
    I have just inherited two broken auto coffee machine from work, one is a saeco odea giro and the other one is a Delonghi Magnifica.
    I have grand plans
    I plan to strip out both boilers and pumps and shoehorn them into my antique italian expresso machine (also broken)
    Basically i want twin boilers and pumps, one set for steam the other for shots
    My plan is to control the temp and pressure precisely with robust electronics
    95deg and 9 bar for shots, 120 deg for steam.

    Now questions: do heater elements run on ac or dc and what voltage?
    can you get adjustable thermostats?
    do you really need closed loop control for temp? i was thinking of an open loop system whereas
    for example say you had and adjustable thermostat and you set the boiler to 100. The heating element switches on then off when the temp reaches 100.
    Now when you pull a shot the heating element is switched on when the pump is running, is this likely to overheat the shot, or will it just be enough to compensate for heat loss.
    could not you play around with the power going to the heater so that precise temp is maintained though the shot?

    cheers
    Perfect (shot) Pat

  • #2
    Re: The Ultimate Expresso Machine DIY

    A couple of things...
    1) There is no need for a second pump for the steam boiler, a 2 way solenoid would be better.
    2) a pressure stat will be better for the seam boiler.
    3) if you want precision in brewing temp, you want a PID.
    4) doing what you plan is massive job that requires a lot of technical knowledge, especially in electronics which by the questions youre asking make it sound like you dont really have - at least yet. I would advise against it , but if you insist, a lot of research and learning will be required.
    5) its spelled "espresso"

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    • #3
      Re: The Ultimate Expresso Machine DIY

      Be careful what you assume, i hold an honours degree in mechanical engineering, and thus could probably design and make a coffee machine from scratch
      The reason i dont think a closed loop heating system is required, is because once the machine is heated up heat loss should be relatively constant with respect to volume of shot.
      Thus you simply need to accommodate for this loss of energy (heat) with controlling you heater coil. You could probably start by reducing system losses by adding insulation.
      oh thanks for the english lesson, not my best subject LOL

      Comment


      • #4
        Re: The Ultimate Expresso Machine DIY

        I disagree about the requirement for a PID, You can probably get away with a reasonable temperature controller running on a thermocouple attached to the boiler

        a PID is slightly overkill really, its all about the deadband your thermostats have, Thermostats tend to be +/- 10 degrees which makes them really poor for things like fine-temperature control with regards to coffee machines (read up on temperature surfing in Silvias as a good explanation of what goes on there)

        Also, Most boilers/heating systems within espresso machines tend to be full voltage, Im unsure what location youre at, but around here (in .au) they tend to be 230/240v @ 10 amp. (IE mains)

        not sure of the exact details of what you may need to do to fit the stuff in there, but Id think that you may have issues with the plumbing of your system if youre adapting a couple of superautos into your antique espresso machine.

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        • #5
          Re: The Ultimate Expresso Machine DIY

          Do you know if those auto m/cs actually have boilers,? or are they thermoblock systems ?
          Temperature controllers .. digital electronic (non pid ) controllers are available as you describe, operating off thermocuples, with adjustable set points. Just search the Evilbay.
          However, a simple on/off control will not give the control you hope for.
          A heating element switched off at 100 deg will continue to "soak" heat into the boiler such that the temp will "overrun" by 5-10 deg ( depending on the relative size of the boiler and the heater element).
          Likewise when the cooling bioler drops to the set 100 deg point, and switches on the heater, there is a time lag befor the water temperature actually stops falling ...again 5 or more deg.
          you will never have a good stable temperature within less than 5 deg or so.
          This is where a PID wins ,..it learns those "lag" factors and compensates, giving precise control to the set point within 1 deg.
          ..Also .. PId controllers are no more expensive than simple electronic temp controllers .< $30

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          • #6
            Re: The Ultimate Expresso Machine DIY

            Originally posted by 2B252C272D7C7B490 link=1333424909/4#4 date=1333615324
            ..Also .. PId controllers are no more expensive than simple electronic temp controllers .< $30
            From where?

            Comment


            • #7
              Re: The Ultimate Expresso Machine DIY

              Originally posted by 7279757D6B687A7D796B747D61180 link=1333424909/5#5 date=1333659169
              ..From where?
              Where would you think ? ....China / Evilbay

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              • #8
                Re: The Ultimate Expresso Machine DIY

                Originally posted by 5762756162647358576673070 link=1333424909/2#2 date=1333581275
                Be careful what you assume, i hold an honours degree in mechanical engineering
                Hmmmm.
                In my experience a mechanical engineer could Design a coffee machine, not doubting that. Theory is not the problem, but it lies with the practical.

                A Mechanical Engineer would take his/her drawings/ideas to an engineering trades-person like myself, who would then go and interpret the drawings, find the problems why it wont work, fix the problems and actually make it

                No disrespect meant but you tell us not to assume

                Originally posted by 5762756162647358576673070 link=1333424909/2#2 date=1333581275
                and thus could probably design and make a coffee machine from scratch
                Then make assumptions of your own.

                Originally posted by 5762756162647358576673070 link=1333424909/2#2 date=1333581275
                heat loss should be relatively constant with respect to volume of shot.
                Disagree with this too. Heat loss factors far exceed just the shots brewed.

                My 2 cents

                Comment


                • #9
                  Re: The Ultimate Expresso Machine DIY

                  Sounds like an awesome project!
                  I agree that a PID is the best way to go. I bought a PID from ebay for $15 including postage.
                  Yes you could use a more basic temperature control if you wanted, But for $15... youd be crazy not to use a PID.
                  I also agree that anything other than a PID will overshoot.

                  Comment


                  • #10
                    Re: The Ultimate Expresso Machine DIY

                    not to sound arrogant (I too have an honours degree in mech engineering) but if you dont know that a thermostat is a closed loop control system youre a fool.

                    Get some books by Illy and itll give you a basic understanding of the design complexities that will be involved.

                    Comment

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