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PID settings for BFC Junior Extra TCI (Diadema in Aus)

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  • PID settings for BFC Junior Extra TCI (Diadema in Aus)

    Gidday from an NZ based noob to this forum.

    I have a BFC Junior Extra TCI dual boiler machine and have question re some of the PID settings that the NZ agent is unable to answer at the moment.

    There are 3 settings that determine the duration and timing of the turning on and off of the elements in the boilers to achieve the desired brew and service boiler temperatures.

    I would like to fine tune these settings to reduce the variation I am seeing in the brew boiler, but the english translation that BFC provide of the Italian version of the manual is a little obtuse to me.

    The settings involved and the descriptions are as follows:

    P. default=7 Where 7 is the value of the constant proportional pid control, which has the function to turn off and turn on the heating element so that most closely matches the set temperature value, more the impulse slows (otherwise the value obtained should be to exceed the set value).

    I. default 0.10 Where 0.10 is the value of the constant integral pid control, which has the function to calculate the accumulation of error (in the case of a coffee machine is very low), that is the analysis of the time remaining to reach default.

    D. default 15 Where 15 is the value of the constant derivative pid control, which has the function to evaluate the heating system (that is, if the temperature is increasing or decreasing) and based on this analysis decides the pulse duration of the heating element.

    What I think I want to do is reduce the period of on time and decrease the gap between temp checking for the brew boiler element as I am currently seeing a variation between 90 and 93 degrees on the panel with the target temp set at 90. So which one(s) to change and by how much in what direction?

    I know this machine is sold in Australia as the Diadema so thought someone more experienced with it may be able to shine a light.

    I will ask BFC as well but I think the issue is in the translation from Italian so I don't know how far I will get there.

    I can post the original italian from that section of the manual if someone is interested in that.

    Last edited by Seakiwi; 23 August 2014, 12:37 PM. Reason: spelling

  • #2
    There are several sets of PID settings for various espresso machines posted on these forums, but as to weather any of these would be ideal for your requirements, I suspect is unlikely.
    however, whilst you are waiting for better information, you have nothing to loose from a little "trial and error" experimentation, since you have already base line settings that you can go back to at any time.


    • #3
      G'day "Seakiwi"...

      Experienced similar characteristics with my Diadema too, from scratch. Basically, I set up a home made Scace Device in a spare Group Handle so that I could monitor real-life performance when pulling shots at standard flow rates. This was to ensure that intra-shot and inter-shot performance was being optimised.

      The setting I ultimately arrived at are as follows...
      P - 2.0
      I - 0.05
      D - 2.5

      You will also need to adjust the Boiler Offset number so that the reported Brew Water Temperature remains reasonably accurate. In our case here in S.E. Qld at Warwick, the Offset needs to be set at 18C in Winter (16-18C daytime ambient) and 16C in Summer (up to 40C ambient). This was established using my "Scace", so no guesswork involved.

      Anyway, hope some of this is helpful and may at least give you a place to start. Always remember though, only ever change one parameter at a time and wait at least 30 minutes between changes to allow the machine to reach equilibrium, before pulling any shots or testing, etc...

      All the best,


      • #4
        thanks guys,

        Dimal, I think the machines sold under the Diadema brand are slightly different to the ones sold here as in I think you have 2 x 1000 watt boilers whereas we have 2 x 1300 watt boilers in the machines here. Interesting the temp offset for the brew boiler here at the moment is 18c as well.

        Did you change the PID settings in sync or one at a time? What were the defaults for your machine?

        So your experience is reducing each of the settings stabilised the brew boiler?

        I'll have to check with the distributer here in NZ and see if I can get my hands on a Scace for more accurate adjustments.


        • #5
          G'day mate...

          Seems like our machines are somewhat different. The Brew Boiler on mine has an 800W element and I think a 1,300W element in the Steam Boiler. I'd recommend that you contact CosmoreX Coffee here in Oz as they will no doubt be able to get you started. For what it's worth though, if your Brew Boiler has an 1,300W element, I'd expect the Integral and Derivative parameters to be set even slightly less than my own; given that the recovery will be a lot quicker. Proportional should be set at around 2.0 to start off with, 7.0 does seem quite a bit too high....



          • #6
            Two good starting points are here
            PID controller - Wikipedia, the free encyclopedia
            and here

            But through a lot of my own testing on my own PID machine, I have come extremely close to the settings which have been calculated from the above theory.
            while not quite as steady as other other methods, it gives quite an aggressive tuning which gives faster re-cycle and faster boiler on when nearing the end of a shot.

            I'm happy with a little overshoot on my machine when re-cycling between shots, as it allows me to flush the group to clean off the shower screen and rinse the PF if needed.


            • #7
              Only problem Rob'...

              There isn't enough information available from Gicar to determine the algorithm(s) being used and other key factors like 'cycle time', etc... In the end I just used standard PID tuning procedures to get close to what I thought was reasonable performance. Straight calc's were very much hit and miss...



              • #8
                Time is measured.. By you.


                • #9
                  Time is measured.. By you.


                  • #10
                    Originally posted by Robbks View Post
                    Time is measured.. By you.
                    ??? - What on earth are you talking about mate?



                    • #11
                      Update, I have recieved the following reply from BFC via the distributor here in NZ:

                      A difference with the multiboiler of professional espresso coffee machines with the Junior TCI, is that the control unit in the Junior must control not only the temperature of the coffee, but also the pressure of the steam in the boiler.

                      So it must control two parameters at once.
                      So it is quite normal to have variations of this type.

                      If we are then to be even more precise and 4 degrees lower than the reading on the display, you will need to modify the following parameters:

                      "P" is currently 7 >>>>>>>> change in 2 "I" is currently 0,10 >>>>> change 0.01

                      These values ​​allow us to have smaller fluctuations in temperature on the display. “

                      So I am now trying these settings with "D" left at its original default, I will update again in a day or so.


                      • #12
                        After a weekend with the new PID settings I am happy with the balance between temp stability and recovery time with these new settings.

                        With the brew boiler temp set at 90 I am seeing it peaking at 92 but only for a second or so and then dropping back to 91 on the display so I suspect it is only just getting above 91.5 then dropping back. Sitting unused it is displaying 90 and 91 only.

                        Pulling a shot sees the temp drop post shot to 89 and sometime 88 but it recovers to 90 in 15 to 17 seconds, which is just fine.

                        There is no noticeable change in the temp displayed for the service boiler temp, it just sits at the set temp continuously, however I think the pressure in the boiler is a little more mobile in that it is varying by .05 bar a bit more and sitting at .05 bar higher at its peak than it was previously. The light showing power to the service boiler is turning on and off a little more, but to be honest I wasn't monitoring this boiler as closely previously so I may just be being more observant.

                        With the power setting for the brew boiler at half power I never see the temp go above 91 or below 90.

                        so all in all now very happy!

                        Now to start playing with the temp of the shot for the different beans/blend I want to try.

                        Edited for error in bar pressure


                        • #13
                          As you have discovered, BFC is an excelent company to deal and they care abnout both their products and their clients. It is still a privately owned, family business. Their machines are well designed and built, very reliable, good performing "quiet achievers"...

                          I've had a succession of them at home over the past 10 years or more.