chlorox What I meant is that would such a cause affect all machines rather than just some?

I have no idea how many machines are sold, affected by a small aberration and unaffected. We also don’t know how the set points are achieved across 3 temp settings with a single PID values. But, ambience can make a difference as the machines with the same settings do behave differently across the user spectrum. We also have examples in the case of Evo.

It will definitely be interesting to understand how Nurri works to maintain the temp.

The bottom line for the users is the cup! Enjoy many years of Nurri and lovely coffee. 😊

LMSC I am also thinking if they implemented some sort of dynamically adjusting (self-correcting) solution internally to reach system to converge to the set points, given the PID parameters are common for all temps? Is that the Delta (Es)?

Otherwise, how could a set PID parameters facilitate 3 different set points?

I don’t know what those ‘Delta’ temperatures are; they appear to be the interval of temperature over which the controller acts as a PID rather than as an on/off switch; if I’m right, the defaults seem to indicate that the Nurri’s default behaviour is to act as a PID controller over the whole range of temperatures from zero to the target. The mechanism of a PID controller is relatively simple:

The desired/Target value of the control variable (temperature for ‘us’, but it could be anything else) is compared to the actual value. The actuator output (for us, current to the heating element) is a function of:

  • A proportion of the difference between the two values (so called ‘error’)
  • The integral of the error over a certain period of time
  • The derivative of the error with respect to a certain interval of time

“mathematically”

I = kP (Tg - Tm) + kI ∫(Tg - Tm)dt + kD d(Tg - Tm)/dt

Where Tm is the measured temperature and Tg is the ‘goal’ temperature

My understanding of the control board in the Nurri is that it allows monitoring of three probes/setting of three independent temperature targets, but it uses the same proportionality constants (kP , kI , kD) for all of them. The Vostok/Evo board contains three separate PID controllers.

The PID parameters should not only ensure that the target temperature is reached, but that it is reached as quickly and as stably as possible. However, even using a single set of parameters should enable some level of temperature control - possibly a very good and stable one.

    tompoland let me know if there are any particular pics you’d like to see.

    Thank you, Tom - much appreciated!

    If you have time, it would be really nice to see overall pictures of the interior layout, and particularly the back of the group and the pump. I’m also curious if the “ACS” modification to the water flow, with the group being filled through a solenoid and outlets into the brewing chamber located below the main piston seal, or whether Nurri/TOF are using some other method. This requires removing the shower screen and compressing the spring, then taking a picture of the brewing chamber; I fully understand if this is not something you want to do now - or at any time in the future!

      CoyoteOldMan Delta’ temperatures are

      When we had the Evo at home, I had in fact played with a software to see what the desired parameter settings should be to reach the set point.

      I think the delta is used for looping through 3 different set points.

      LMSC am correct, the 1C undershoot was t3 (group).

      Double and tripled checked: that’s correct and @chlorox I can confirm that T3 is set to 93 but this morning stopped at 92, then 91.

      I don’t know if I simply misread it the other day but I’ll keep an eye on it.

        CoyoteOldMan

        Sounds like fun and useful for the review.

        I’ll have a crack at it this weekend.

        But if I break it then I’ll need you to pop over and put it together again. I’ll even pay for the bus ticket. 😀

          I’ll have a crack at it this weekend.

          That’s Aussie slang for attempting something, btw. Tom (hopefully) won’t be cracking his machine.

          CoyoteOldMan

          Maths was never my atrong point and I probably understood only a small proportion of what you typed but I think I see the gist of what you meant…

          I should say that nonetheless in practice the system takes quite quickly to reach the targeted temperature for all three components and doesn’t fluctuate much upon getting there, so I don’t think it makes any tangible difference performance wise.

          • LMSC replied to this.

            CoyoteOldMan

            Sorry for maybe asking a rookie question but you mean that the way used in the vostok and evo to fill the groupheas differs from the typical LSM grouphead design?

              tompoland

              Did you try to experiment by changing to different temps for t3 to see if the same shortfall is consistently happening? If so then the patch may also be applicable to your machine.

                chlorox seems to be one or two degrees short. I adjusted T3 to 95c this morning and it seemed to stick to 93c all morning.

                chlorox Sorry for maybe asking a rookie question but you mean that the way used in the vostok and evo to fill the groupheas differs from the typical LSM grouphead design?

                As far as I know, yes - I believe on the original LSM group the position of the seals and the placement of the water ingress is different.

                chlorox I should say that nonetheless in practice the system takes quite quickly to reach the targeted temperature for all three components and doesn’t fluctuate much upon getting there, so I don’t think it makes any tangible difference performance wise.

                • What’s the range you are getting across t1 to t3 once the machine is fully warmed up and stable - after 30 mins?

                The default setting looks fine, IMO, for the brew boiler; it closely resembles our settings, although we have another parameter (B) for the PID, which seems not relevant here.

                • Ignoring the steam boiler, the P value especially is perhaps not sufficient for the group. Most of us would have a higher P for the group (like 2) compared to the brew boiler (like 1). But, I won’t change it until the patch arrives. as it is common for all the ts

                The way I have understood the PID is as follows. This understanding is on the basis of my chats with Dave in the past and fiddling with my Evo extensively!

                • The P (Proportional) applies power to the heating elements in proportion to how far you are from the set point. Its main drawback is that the closer you get to the set point, the less power it applies. A smaller value of P in increments might make the group very slow to recover, too large and you might get overshoots.

                • The D (derivative) acts as a kind of a balancer in simple terms. It measures the change over speed. It acts like a brake or a dampener on how much power the P uses. The low values of D can cause overshoots; and, the high values of D can make response sluggish.

                • The I (Integral) tries to even out the difference of the time spent above and below the set point. If you’ve set 93C as your set point and spent 30s running below, it will try to push the group over to 93C for similar amount of time. This action compensates for P’s inability to make that last effort. It is not advisable to change it from the default value, unless one knows what is being done and the effect it can have. A small change can have a larger effect.

                  LMSC one of the problems of having proportional and a positive value of B (temperature range at which the controller works as a p i d); Steaming power is reduced.

                  This is because when steaming the temperature of the boiler is always a degree or two below the setpoint, and that means the proportional value is always trimming down the power applied to the heating element because it’s near the set point and because B is a positive value it’s acting like a pid. This is exactly what we don’t want when steaming, we want the p&id really to act as a pure on off controller with no proportional limiting. On the early duetos where they started using the pid with shared parameters to control the steam boiler, steaming power was reduced by about 20% vs the earlier models which used a pressurestat. I’m assuming the change on the new Nurri might be to have three lots of pid parameters, in which case the steaming could probably be improved.

                    I’m no expert on steaming Dave but on the couple of occasions I’ve played with the steam wand the steam coming out is tremendously powerful. It’s honestly hard for me to imagine needing anything stronger, it looks as powerful as a freaking rocketship.

                    But I rarely steam and when I do it’s only for guests and I use the Decent which is seriously unimpressive steam-wise compared to the Nurri. So I’m hardly the voice of experience when it comes to steaming.

                    But maybe @chlorox has more experience in the steaming department.

                      tompoland

                      I have no issues with the steaming power of the nurri, coming as I was from the izzo pompei that had steam power that was so over the top thar it seemed enough to flash fry a goose (half joking lol)…

                      LMSC

                      As a neo-Luddite who would have had great difficulty programming a vcr in the old days, i am just going to pretend I understood that LOL

                      tompoland I rarely steam and when I do it’s only for guests and I use the Decent

                      Sorry for the slight OT, but why do you use the Decent for guests? I’d show the Nurri off - it’s much prettier and more theatrical…