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Ethiopian aspirin - bitter espresso - wet pucks

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  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Gday again Matt,

    Glad to hear that its all coming together now mate, the little PIDd Mokita really does pull some fantastic brews. Talking about chilly, I dont think were even going to make an 8 C maximum today .... the fires already going, the fur babies sorting out their places in front of it and about to knock up a brew of Grendels Zimbabwe roast. Couldnt be better ;D,

    Mal.
    P.S.
    As it happens, I do know a bit about Heat-Pumps..... Any questions about em just send me a PM .

    Leave a comment:


  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Originally posted by Mal link=1180678692/15#24 date=1181313695
    Originally posted by matblack link=1180678692/15#23 date=1181236009
    I flush my portafilter and the PV drops of course.  Then it raises again to 102 or thereabouts.  Then after I finish <i>the grinding</i> I lock the portafilter back in and the temperature shoots up to 111-12.
    Dont know why you are flushing the PF before pulling a shot, its not necessary with a PIDd Mokita... Provided that you have left the PF nipped in to the Group while the machine was heating and allowed to reach equilibrium, all you need to do is walk up, grind your coffee, remove the PF and dry out the basket, dose, distribute and tamp, lock the PF into place and pull the shot. If you are pulling one shot after another, by the time you have ground the next dose of coffee, knocked the old puck out, wiped the PF Basket clean and dry and repeated the dose, distribution and tamp.... the PV should have restabilised very close to SP and youre ready to pull another shot... and so it goes.

    I think that all is happening is that the flush routine you are using is introducing so much fresh water into the boiler that the controller is winding up to the higher temperature as a result of thermal inertia trying to overcome the sudden and significant energy demand being placed on it. Theres nothing wrong with the controller at all. This is NOT a Heat eXchanger machine so does NOT require a cooling or heating flush, its designed to be ready to go ad infinitum from a walk-up start.
    Thanks Mal

    That really is very helpful.

    After actually taking the lid off this morning for a look and following the circuit through, Ive got a slightly better understanding of how the thing works. I took a photo for reference as well.

    As I mentioned earlier, Im more of a Jaycar wannabe than an electrical fitter and was thinking out loud in that last paragraph. It occurred to me that maybe bumping the machine by locking the portafilter back in could displace the water through the boiler and cause a brief fluctuation in temp. But I see thats not a problem.

    I guess thats sort of what I was doing by preflushing, which as you said does displace a relatively large amount of both cold and hot water and cause a significant change. I wont do that anymore.

    Anyway, thanks for the informative tute--I scanned it just now, but Im going to have to take some time to get my head around it.

    After work yesterday morning I pulled some terrific double shots so I was pretty sure the thermocouple was working fine. Its all starting to come together. The Ethiopian Harrar just arrived in my surprise pack, Ive got the grinder dialled in, my tamp is pretty good and Im pulling these delicious well extracted shots of almost pure crema in just over 25 seconds. Life doesnt get much better than this.

    Except it is kind of chilly . . . Incidentally, do you know anything about heat pumps?


    (Joke.)

    Leave a comment:


  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    OK thanks. Ill open it up and take a photo anyway, because I want to get my head around how it works. For reference, is the thermocouple mounted at the boiler?
    Yep, in the original position the t/stat used to occupy and thats where Id leave it.

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    Couple of quick questions:

    What kinds of factors create signal noise and could influence PV?
    The t/couple I used is fully shielded and NOT affected by EMR.

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    Bullitt mentioned some electrical interference from switching by the Relay which gives an artificially high reading for a few seconds.
    I wouldnt get too hung up on this kind of thing, its not an issue with your setup.

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    So how much does the PV usually fluctuate by?
    Depends on the activity youre doing at the time really.... Assuming equilibrium at a SP of 102C and you pull a 60ml shot, the PV could go down as low as an indicated 85-90C but it isnt really relevant because the inrush of fresh boiler water drives this number below the actual brew water temp. Providing the controller is still set up the way I had it, the Derivative will immediately sense the change in temperature and drive the output fully ON. The PV should quickly rise to SP and be quite stable within a very short time.

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    I flush my portafilter and the PV drops of course. Then it raises again to 102 or thereabouts. Then after I finish <i>the grinding</i> I lock the portafilter back in and the temperature shoots up to 111-12.
    Dont know why you are flushing the PF before pulling a shot, its not necessary with a PIDd Mokita... Provided that you have left the PF nipped in to the Group while the machine was heating and allowed to reach equilibrium, all you need to do is walk up, grind your coffee, remove the PF and dry out the basket, dose, distribute and tamp, lock the PF into place and pull the shot. If you are pulling one shot after another, by the time you have ground the next dose of coffee, knocked the old puck out, wiped the PF Basket clean and dry and repeated the dose, distribution and tamp.... the PV should have restabilised very close to SP and youre ready to pull another shot... and so it goes.

    I think that all is happening is that the flush routine you are using is introducing so much fresh water into the boiler that the controller is winding up to the higher temperature as a result of thermal inertia trying to overcome the sudden and significant energy demand being placed on it. Theres nothing wrong with the controller at all. This is NOT a Heat eXchanger machine so does NOT require a cooling or heating flush, its designed to be ready to go ad infinitum from a walk-up start.

    Originally posted by matblack link=1180678692/15#23 date=1181236009
    The grinder is on the same powerboard as the machine and probably could cause interference. There also could be a little slosh of boiler water which could be what? Process noise?
    Nope, the grinder wont be causing any problems and Im not sure what youre trying to describe in the rest of your paragraph?[/QUOTE]

    And thats about it Id say Matt.... In essence I believe you are creating hardship for yourself by not understanding the physics of the processes under control. There are several excellent PID guides to be found on the Net and I think it would be worth your while to try and gain an understanding of the relationships involved between the various aspects of the PID algorithm. One such source can be be found here. All the best mate,

    Mal.

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  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    OK thanks. Ill open it up and take a photo anyway, because I want to get my head around how it works. For reference, is the thermocouple mounted at the boiler?

    Couple of quick questions:

    What kinds of factors create signal noise and could influence PV?

    Bullitt mentioned some electrical interference from switching by the Relay which gives an artificially high reading for a few seconds.

    So how much does the PV usually fluctuate by?



    I flush my portafilter and the PV drops of course. Then it raises again to 102 or thereabouts. Then after I finish <i>the grinding</i> I lock the portafilter back in and the temperature shoots up to 111-12.

    The grinder is on the same powerboard as the machine and probably could cause interference. There also could be a little slosh of boiler water which could be what? Process noise?

    Anyway, Ill take a look.

    Leave a comment:


  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Probably under Industrial Control Supplies and Service, or some variation thereof. Maybe one of our members can help you out more directly as Im not familiar with whats on offer in the Melbourne region but I do know that we have a few engineer members in CS so someone may be able to help you out. Best of Luck,

    Mal.

    Leave a comment:


  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Bummer.

    So who should I look for in the yellow pages?

    Leave a comment:


  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Originally posted by matblack link=1180678692/15#18 date=1181194805
    Then I lock the portafilter back into the lugs and the PV shoots straight to 111-112C.
    Yeah, this is weird :-?,

    Sounds like there could be an "earth loop" situation going on but without being able to check under the bonnet via remote control, I dont have the means to help you troubleshoot the problem. This should NOT be happening and I would advise taking it to someone with industrial control knowledge to suss out what is actually going on. The PV and the SP settings should be absolutely stable unless there is an actual physical change in the boiler or you make changes from the front panel.

    Until the problem is rectified Id recommend that you cease using the machine as you dont know if something hazardous could be waiting to rear its ugly head. I know you probably dont want to hear this but its better to be safe than sorry. All the best,

    Mal.

    Leave a comment:


  • Bullitt
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Um, err, Mal..... where might you be?

    His recommended set-point sounds about right.
    If it is as quick a change in temp as you describe, it sounds odd.
    I know I get some electrical interference with my PID from switching by the Relay, which gives an artificially high reading for a few seconds.

    But to jump up by 9-10 deg is unusual, and it may not be a true temperature reading, in which case your flushing could be causing a low brew temperature.

    Do you have access to another temperature measuring device, such as digital multimeter with a thermocouple? It would be easy to temporarily set it up and compare readings with the PID display, or maybe Mal can offer some more insight as he is more familiar with your equipment.

    Regards
    Bullitt

    Leave a comment:


  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Setpoint 102 degrees C (Mal reckons this is equivalent to 93-94 degrees at the top of the portafilter).

    One thing I notice: I turn on the machine and leave it for awhile. I flush and take the portafilter out. The PID eventually finds a PV of 102C. While Im diddling with the portafilter, wiping, dosing, tamping etc, the PV is constant at 102C.

    Then I lock the portafilter back into the lugs and the PV shoots straight to 111-112C.

    Why is this so?

    I dont want to leave the portafilter in there for five minutes with coffee in it, because it almost guarantees a sloppy puck and bitter espresso. So I either take the portafilter out and flush through the group or expel water through the steam wand to bring the PV down.

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  • Bullitt
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    One other point that hasnt been made,
    what temp setting is your PID showing,
    and where is the temperature reading being taken, usually at top of boiler.
    If all else doesnt totally fix the problem,
    some bitterness could be due to too high brew temp as well.
    But as Mal and others said, only change it by 1 deg at a time,
    and if the your unit has been set as per Mals recommendations it should be pretty right!

    Regards
    Bullitt

    Leave a comment:


  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Great to hear mate ,

    Wont be long now before youre wondering what all the fuss was about . I dont know why it is exactly, but most people seem to start off with grind settings that are too fine and then try to work back from there..... much easier to go the other way.

    Dont hesitate to give me a yell if you think I can help you out with anything to do with the Mokita, a great little machine, sort of like the "pocket rocket" of espresso machines in my view and the PID controller just makes it so much sweeter to use. All the best mate and happy brewing,

    Cheers,
    Mal.

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  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    I think the guide Im following (coincidentally) is the one you wrote, Mal. Aaron forwarded all the documentation with the machine.

    Incidentally, the schematic you drew of the PID is really very clear and easy for even a Jaycar Eggtimer head like me with only very slight knowledge of circuits more complicated than the flashing boing boing light I use to amaze and impress my friends.

    And after setting the grinder at 0.6 for these Costa Rican beans, overdosing, leveling, then tamping hard, Im starting to get closer to the optimum pour times with increasingly more delicious ristretto results.

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  • Dimal
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Originally posted by matblack link=1180678692/0#13 date=1180759184
    Ive been backflushing regularly. Im pretty sure the problem is with my technique and grind. Ill keep at it.
    As mentioned above,

    Not directed at anyone in particular, but if you follow the steps laid out in any number of guides to be found on the Net, like this one for example, you wont risk any harm to your Mokita/Quaha/Fenice style of machine... it really is essential that it is regularly performed to avoid a "tar-like" build up of rancid coffee oils that really does taste very nasty ,

    Mal.

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  • matblack
    Guest replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Ive been backflushing regularly. Im pretty sure the problem is with my technique and grind. Ill keep at it.

    Leave a comment:


  • JavaB
    replied
    Re: Ethiopian aspirin - bitter espresso - wet puck

    Sullo,

    If it was me - Id definitely backflush - it really is required! And wont do any harm if the instructions are followed.

    And if you are worried about warranty - just forget that you have done it

    Leave a comment:

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