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  • Silvia PID Control Queries

    Originally posted by robusto link=1177023968/0#1 date=1177059656
    Just a little curious about your PID setting at 95º, though... where is the thermocouple mounted? Seems on the low side.
    Sure does :-?

    Mal.

  • #2
    Re: Absolutely magnificent 50/50 blend

    My thermocouple is mounted on the top of the boiler and I assume has been adjusted specifically for the temp of the water coming out of the brew group- I have tested it.
    I have been experimenting with various temps. That one is my latest trial temp.
    RH

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    • #3
      Re: Absolutely magnificent 50/50 blend

      Gday RH,

      Just to make sure youre getting the right water temp on top of the coffee puck, it would be a good idea to place a small bead t/c right in there and see what you read on a DMM, after checking calibration/offset of the t/c with boiling water.

      You should be getting the nominal 88-96C on top of the puck when your pour starts with a very slight droop of 1-2C by the time the pour is finished. Reading 95C on top of the boiler seems wrong to me from my own personal experience and of everything Ive read about the Silvia with PID Boiler Control. Itll be worth doing mate, even if just to prove that youre current setting is ok ......If wrong though youll notice an enormous improvement of the flavour in the cup and overall performance of the Silvia. All the best,

      Cheers,
      Mal.

      P.S.
      Ive just completed a quick search through a few sites where Silvias have been modified to PID Control and the Setpoint range that nearly all of the owners of said modified machines use, lies within the very narrow range of 107.5 - 109 C for a t/c location on top of the boiler.

      Comment


      • #4
        Re: Silvia PID Control Queries

        Temperature differences on the order of 15C between the top of the boiler and the brew chamber water are common on single boiler machines. The difference is closer to 17C on the Alexia I am working with right now.

        But sometimes the calibration offset value in the PID controller is set to compensate for this difference.

        Sorry for coming into this conversation late (I dont know all the particulars), but perhaps RHs controller has a calibration offset value that compensates for the temperature difference??

        Jim

        Comment


        • #5
          Re: Silvia PID Control Queries

          Hi Jim,

          Yes mate, very true...... Thats why I thought it would be a good idea to make sure just what the water temp on top of the puck is. If its identical to the Setpoint then there is an Offset, if a difference, then either the Setpoint or the Offset needs to be adjusted. Didnt want to confuse the issue too much at this stage thats all,

          Mal.

          Comment


          • #6
            Re: Silvia PID Control Queries

            Originally posted by Mal link=1177068971/0#4 date=1177253871
            Yes mate, very true...... Thats why I thought it would be a good idea to make sure just what the water temp on top of the puck is. If its identical to the Setpoint then there is an Offset, if a difference, then either the Setpoint or the Offset needs to be adjusted. Didnt want to confuse the issue too much at this stage thats all
            Good point. Measuring the water at the puck is certainly the way to go.

            FWIW, I dont care much for using the Offset for this anyway (if indeed thats the case here). Seems like a complication that doesnt add much value. Plus, most controllers need a little sensor adjustment anyway, and you lose the ability to dial this in.

            Jim

            Comment


            • #7
              Re: Silvia PID Control Queries

              Originally posted by PIDKits link=1177068971/0#5 date=1177255345
              FWIW, I dont care much for using the Offset for this anyway (if indeed thats the case here). Seems like a complication that doesnt add much value. Plus, most controllers need a little sensor adjustment anyway, and you lose the ability to dial this in.
              Same here Jim,

              Much prefer to run with live temp for the reasons youve mentioned and also if you use the controller for steam as well, then the offset doesnt mean a thing and only serves to add to the confusion overall. Keeping it simple is a good thing

              Mal.

              Comment


              • #8
                Re: Silvia PID Control Queries

                Heres how I calibrated mine- taste!
                Using one of Jims kits, and knowing that the offset would be different for the botticelli (and my sons quaha) I first set it at the 108C for a Silvia- the water steamed and hissed.
                I dropped it down to 104 and found the espresso still a bit on the hot and scalded side.
                To reassure myself that I was being level headed, I got my daughter who is an apprenticed chef and has some degree of taste(!) and we made espressos at set points 101, 102, 103, 104, 105.
                We agreed that for espresso 102 was sweetest but for milk drinks, 103 gave that little bit of a bite.
                following this, some blends and roasts like that little bit of adjustment in temp- stability and repeatability arent the only values of PID- adjustability is another!
                Off to make first coffees of the day
                Brett

                Comment


                • #9
                  Re: Silvia PID Control Queries

                  Originally posted by PIDKits link=1177068971/0#3 date=1177253492
                  Temperature differences on the order of 15C between the top of the boiler and the brew chamber water are common on single boiler machines. The difference is closer to 17C on the Alexia I am working with right now.

                  But sometimes the calibration offset value in the PID controller is set to compensate for this difference.

                  Sorry for coming into this conversation late (I dont know all the particulars), but perhaps
                  RHs controller has a calibration offset value that compensates for the temperature difference??

                  Jim

                  Hi Folks,


                  RH asked me about how he should reply to Mal on this topic when he was around yesterday for coffee, unfortunately I was busy making coffee at the time, then forgot to explain my thoughts to him :-[

                  Briefly, RH bought his Silvia complete with the PID already fitted and set up.
                  Initially we wondered about the temp setting, but have tested water coming out the brew head using a bead type TC and yes there is some sort of offset programmed into the setup as far as we can tell.
                  Also there was no manual supplied with the PID controller so re-programming is not something I would be considering at this stage, but it works fine anyway so probably better to leave alone

                  Also another interesting point is that the original brew thermostat has been removed (but was supplied with Silvia) and the TC for the PID is fitted into the original bracket with some sort of packing.

                  Regards
                  Bullitt

                  Comment


                  • #10
                    Re: Silvia PID Control Queries

                    Yeah! What he said! 8-)
                    rh

                    Comment


                    • #11
                      Re: Silvia PID Control Queries

                      Gday RH and Bullitt,

                      LOL, nothing like a combined effort ;D..... Sounds like your t/c is sited appropriately so there should no problems from that end and would indeed seem as though an offset has been programmed into the unit. If you can identify the make and model of the controller I can try and search for a setup manual and see what can be done, if you would like the unit to be working without the offset that is. As Brett mentions above, final adjustments should always be based on taste but for initial setup, as with any kind of control system, its a good idea to kick off with a median setpoint and then move from there as required and according to taste.

                      RH, do you use your controller for Steam Generation too or is it just setup for Brew Water control? If youre happy to leave the unit as is and keep working with the offset in place then thats fine of course. It would still be a good idea though to verify the water temperature on top of the puck after an hour or so of warm-up time, just to make sure there is no discrepancy between the indicated temperature and the actual in the Group. Measuring the water temp at the PF Spout is not really ideal either as there will be a few degrees of temperature gradient between this location and directly under the shower screen. It really is worth going to this small amount of effort initially as it is basically a once off procedure to establish actual operating conditions for your unit so that fine adjustments can be made and allow you to know exactly where you are under all operating conditions. Well, I like to know exactly whats going on but doesnt mean you or anyone else has to be this pedantic of course, its just my nature Im afraid .

                      Cheers,
                      Mal.

                      Comment


                      • #12
                        Re: Silvia PID Control Queries

                        If it tastes good, thats the indicator--BUT...there is always in my own mind anyway, that niggling doubt that it might taste BETTER if all variables were pulling together correctly.

                        So Mal, Im with you, and I would be eager to know the temperature of water hitting the puck. As I said, thermocouple measurements taken anywhere elsewhere are a mere reference point only.

                        I must say, though, this is the first time Ive come across offsetting the PID itself for the top of boiler/grouphead variation.

                        Ive offset the PID for a degree or two as a calibration, so that boiling water is read as 100º, but thats all.

                        If someone else has done the major 15º offset, I would want to reassure myself by taking a reading at the group head.

                        The way to do that, of course, is to use a cut down polystyrene cup, preheat it, throw out the water, completely enclose the group with it, and poke a thermocouple near the top so it comes out just under the shower screen.

                        --Robusto

                        Comment


                        • #13
                          Re: Silvia PID Control Queries

                          Actually guys,

                          I have found it easier and a lot less mucking around to do it the way Sparky does, over the lip of the basket with the t/c bead sited close to the middle of the (sacrificial) puck and then lock the PF in and go for it. So long as you tighten the PF in position as per normal it seals ok around the t/c cable, also puts a bit of a kink in the cable too but nothing serious enough to cause short-term failure of the cable. Of course, it has the major advantage of reading the temperature during actual shot pouring conditions and this data can then be considered to be empirical for your machine, for all practical purposes.

                          Worth doing, I can vouch for it....

                          Mal.

                          Comment


                          • #14
                            Re: Silvia PID Control Queries

                            [OOPS - posted this before I saw Mals reply. Sorry for the duplication]

                            Ill offer a bit of a caution regarding measuring brew temps on the Silvia (and probably most other machines). Because of the dynamics* of the system, the temp delivered to the brew chamber is very dependent on rate of water flow.

                            The only way to measure the temps the coffee will experience is to reproduce the same flow (60ml in 25 seconds or thereabouts).

                            The Scace Thermofilter does this by using a restrictor on the outlet. This is by far the easiest way to get repeatable, fairly accurate numbers.

                            But the most reliable, and cheapest, way is to feed a fine wire t/c over the lip of the basket and pull a real shot. You can only use your t/c this way a few times (less than a dozen I would estimate) before the repeated pinching wears off the insulation and creates a false junction. But until this happens, you should get pretty good data.

                            * amount of cold water entering the boiler, contact time of brew water with the group, etc.

                            Jim

                            Comment


                            • #15
                              Re: Silvia PID Control Queries

                              Newb question -

                              Why cant you just remove the basket and feed the t/c up the spout?

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