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Thread: Decent espresso

  1. #1431
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    Quote Originally Posted by Dylan View Post
    John - How does a machine like the Sage DTP or DB manage it's temperature after the Thermoblock? If it is as inaccurate as you say (which I dont doubt) I assume they must also be employing some kind of method to stabilise the temperature before it hits the puck?
    The Sage DB (also known as the BDB = Breville Double Boiler) uses a boiler (actually 2 boilers, one for steam, one for hot water), and my understanding is that it also electrically preheats its group head like we do. The reviews I've seen is that the Sage DB/Breville DB have quite good temperature accuracy.

    The thermoblock photo I posted was for the less expensive Breville/Sage 800 model, which appears not to be boiler based, and likely has thus less accurate water temperature.

    You get what you pay for, and Breville/Sage quite reasonably has a product line at different price points, with different quality of different prices.

    Quote Originally Posted by roastini View Post
    The water in the tank is heated to about 50°C (or at least that was the design as of some time ago).
    This was true a year ago, but we no longer heat the water tank, unless it is under 15ºC, in which case we bring it up normal ambient temperature of 20ºC. This is to handle the case of someone using refrigerator water to refill our tank.

    So, the discussion about problems that could occur with a hot water tank are no longer applicable. We now store enough heat in the metal of the water heater that we don't need to preheat the tank.

    Quote Originally Posted by roastini View Post
    I believe that on a plumbed machine (a DE1PRO+) when low water is sensed the incoming water replenishes the supply tank, which is then heated to 50°C. During the wait while the tank comes back to temp, I believe you cannot make espresso. I think this takes a matter of minutes. The DE1 and the DE1+ do not have the capability to be plumbed in, so on those machines there would be a low water indicator, and the user refills the tank, which then needs to be heated prior to making espresso.
    Topping up the water tank is synchronous on the DE1PRO+ and occurs at a rate of 13ml/second. A typical espresso + steaming takes 100ml of water, so about an 8 second delay per espresso. The "refill point" can be set to be after every espresso, or once the tank gets low, so you can choose to wait a little bit after each shot, or less frequently but for a longer time. This is for the DE1PRO+.

    On the DE1CAFE we use a bigger power supply, and so we're able to synchronously refill the tank, and thus no user delay.

    Since we no longer heat the water tank, there is no delay after refilling before you can start using the water.

    Note that the water tank does heat up a little bit with use, from the getting-the-system-up-to-temperature that occurs before each shot. This typically compensates for the 12ºC water that is coming in if you're plumbed.

    -john
    Last edited by decent_espresso; 07-02-18 at 05:37.

  2. #1432
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    Quote Originally Posted by John Doe View Post
    If we buy a grinder through Decent, can you make the upgrade for us? If so, what would the final cost of that be? I'd rather just receive it ready to go!
    Yes, once we have stock of the SSP burrs (~6 weeks), we'll be offering a +~USD$200 option to have SSP burrs in the grinder, instead of the standard ItalMill burrs. For replacement-due-to-wear, we'll offer both the ItalMill and SSP burrs, at something like ~USD$100/USD$200.

  3. #1433
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    Default Calibrating to Reality

    calibrating.jpg

    Our "first production machine" is now up and running, and we're working through the final problems before making a lot more identical machines.

    Here's what we've found so far:

    FLOW METER DIDN'T WORK
    It turns out that which-wire-does-what changed between model numbers and so our flow meter cables need to have their pins re-arranged. This takes about 30s per cable, and Jennifer can be seen doing this on the top left.


    CALIBRATING PRESSURE
    Photos: left middle, top right.
    Next, we got to test the calibration steps that I've written for the Android tablet. Why do we need to do this? Because: the specifications a manufacturer gives us for a part aren't necessarily what you actually get. The pressure sensor comes with a "magic number" to convert resistance to pressure, but physical variation means the "magic number" will be slightly off. To test the pressure, we use a Scace II portafilter, which is a $600 piece of test equipment that independent reports pressure and temperature. We then change the "magic number" in our pressure sensor so that our readings now agree with the Scace. 91PSI=6.27 bar, so we were 4.5% off until calibrating.

    Incidentally, on the middle-left photo, you can see the cooling effect of the unheated stainless steel mass of the Scace 2. Our temperature probe is reading the effect of this cooling, and our water mixing technology tries to compensate for it by putting in hotter water. In this case, a -2.5ºC cooling effect was over-compensated for between seconds 10s->25s. Running a hot water shot or two, to preheat the Scace, would remove this temperature fluctuation at the puck.


    CALIBRATING FLOW
    Photos: bottom right and left.
    Using the Bluetooth scale to measure flow rate into the cup, we can obtain an accurate flow measurement, based on weight rather than moving water. At lower speeds to water, the flow meter readings get quite noisy (see on the oscilloscope) and a bit of tweaking on the noise filter was needed to make this wor better. Here, the calibration was needed to correct a 4% to 8% error.

  4. #1434
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    Quote Originally Posted by decent_espresso View Post
    calibrating.jpg

    Our "first production machine" is now up and running, and we're working through the final problems before making a lot more identical machines.

    Here's what we've found so far:

    FLOW METER DIDN'T WORK
    It turns out that which-wire-does-what changed between model numbers and so our flow meter cables need to have their pins re-arranged. This takes about 30s per cable, and Jennifer can be seen doing this on the top left.


    CALIBRATING PRESSURE
    Photos: left middle, top right.
    Next, we got to test the calibration steps that I've written for the Android tablet. Why do we need to do this? Because: the specifications a manufacturer gives us for a part aren't necessarily what you actually get. The pressure sensor comes with a "magic number" to convert resistance to pressure, but physical variation means the "magic number" will be slightly off. To test the pressure, we use a Scace II portafilter, which is a $600 piece of test equipment that independent reports pressure and temperature. We then change the "magic number" in our pressure sensor so that our readings now agree with the Scace. 91PSI=6.27 bar, so we were 4.5% off until calibrating.

    Incidentally, on the middle-left photo, you can see the cooling effect of the unheated stainless steel mass of the Scace 2. Our temperature probe is reading the effect of this cooling, and our water mixing technology tries to compensate for it by putting in hotter water. In this case, a -2.5ºC cooling effect was over-compensated for between seconds 10s->25s. Running a hot water shot or two, to preheat the Scace, would remove this temperature fluctuation at the puck.


    CALIBRATING FLOW
    Photos: bottom right and left.
    Using the Bluetooth scale to measure flow rate into the cup, we can obtain an accurate flow measurement, based on weight rather than moving water. At lower speeds to water, the flow meter readings get quite noisy (see on the oscilloscope) and a bit of tweaking on the noise filter was needed to make this wor better. Here, the calibration was needed to correct a 4% to 8% error.
    Really interestimg to read and exciting. You guys are so close now!

    A couple of questions for you John:

    1- Are you expecting any needs for self calibration after some time? I would assume the pressure sensors will not stay calibrated forever... And if so, how do you intend to do it?

    2- How does water temperature affect the pressure reading and pump operation? Is the machine running "blind" until the water gets to the puck sensor and the starts adjusting from there?

    Good luck for the upcoming weeks!

  5. #1435
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    When are the first machines now due to people ? Not that I have ordered one, am just interested in where Decent are with this now.
    #Beans not machines- all welcome - where we taste and swap beans
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    Quote Originally Posted by Mrboots2u View Post
    When are the first machines now due to people ? Not that I have ordered one, am just interested in where Decent are with this now.
    We'll be verifying the calibration this week, and stress testing the 10 machines for 7 days before sending them to anyone.

    In about 2 weeks, we'll send 8 machines to my beta testers.

    About 2 weeks after that, we'll start shipping machines to the ~100 USA buyers who indicated they wanted pre-UL certification.

    So, about 5 weeks away.

    There's a 50/50 chance that we'll have UL certification around then, so maybe the those first machines will be UL certified. As soon as we have UL certification, we'll start the CE (and worldwide) certification process, so that we can send out the final 100 non-USA machines.


    Quote Originally Posted by Andreugv View Post
    1- Are you expecting any needs for self calibration after some time? I would assume the pressure sensors will not stay calibrated forever... And if so, how do you intend to do it?
    Other than calcium buildup on the sensor itself, or moving to altitude, we don't know of anything that should make the calibration drift. I'm not saying it's not possible, just that we don't know of anything right now.

    However, to directly answer your question, if you have access to a Scace portafilter, you'll be able to run a 6 bar shot, and through my tablet software, enter in "goal pressure vs measured pressure", to recalibrate.

    However, a more likely need for recalibration is if a sensor breaks and is replaced with a non-identical sensor. Recalibration will then be essential.

    Quote Originally Posted by Andreugv View Post
    Is the machine running "blind" until the water gets to the puck sensor and the starts adjusting from there?
    There are 9 temperature sensors on the DE1, so we do way before the puck what the water temperature is looking like. 3 of those measure "metal temperature" (group head, and the two water heaters).

    There is only one pressure sensor, but because there is water present in all tubes at all times, any change in pressure anywhere is instantly registered on the pressure sensor. It's one big pressurized system. We do not do what most espresso machines do, which is measure pressure behind a flow constrictor, thus measuring only the pressure between the pump and the constrictor.

    Quote Originally Posted by Andreugv View Post
    2- How does water temperature affect the pressure reading and pump operation?
    I'm unsure just how "deep" a question you meant to ask here.

    Because we're performing water mixing with two pumps (hot and cold) while simultaneously controlling pressure and overall (mixed) flow, the control system to do this is "non-trivial" and indeed is mostly what has taken about 2 years to figure out.

    -john
    Last edited by decent_espresso; 10-02-18 at 09:08.

  7. #1437
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    Default Down to the wire

    down_to_the_wire.jpg IMG_7981.jpg

    We are color coding all our wires and sensors in 11 different colors, using a colored fiber sleeve.

    To make the colored sleeve, we've been using our automatic-tube-cutting machine, and then cleaning up the splayed mess (bring right tubes next to Josephine's left elbow) with a hot air gun (bottom left photo).

    The resulting tube no longer splays (blue tube in the bottom right photo) but it looks sloppy and takes up precious space next to other connectors on the PC boards. I've not been happy with this, and have looked to improve it.

    This week, a temperature controllable "hot wire knife" arrived, and the results (grey tube, bottom right photo) are so much better.

    You can see Josephine in the photo redoing the already-cut tubes so that they have a clean, melted cut. I'm not super-happy with the safety aspects of this process, so we'll be soon making a plastic guard with a "cut slot" in it, to prevent an accident.

    And speaking of accidents, many thanks to Jeff W on Coffee Forums UK for bringing to my attention the risks of loose hair in the shop, which he noticed in one of my recent photos. A humorous "hair on fire" poster now graces the shop wall, and we'll order a shop helmet after Chinese New Year.

    safety.jpg

  8. #1438
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    Default Getting organized

    getting_organized.jpg

    Our espresso machine factory is slowly starting to look a bit civilized, as we prepare to ramp up production (and hire more people) in about 5 weeks from now.

  9. #1439
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    What about uk/eu orders whats the time frame for these?
    #Beans not machines- all welcome - where we taste and swap beans
    https://www.facebook.com/groups/503036363197361/
    I wrote a blog, it's nothing to do with coffee ...
    https://rjwinc.wordpress.com
    Instagram
    rjw_inc

  10. #1440
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    Quote Originally Posted by Mrboots2u View Post
    What about uk/eu orders whats the time frame for these?
    Mid-April is my guesstimate for starting to ship "the rest of the world", if I assume UL certification completes mid-March, and that CE/World compliance takes a month.

    The two big variables are:
    1) what hurdles remain to UL and CE compliance
    2) how quickly can we ramp up machine production speed and manpower. It currently takes about 5h of manpower per machine.

    In March, Mat North will receive a DE1+ at his café in Bristol.

    He's been a key technical and coffee advisor for some time and while we still have some details to work out, the plan is that he'll be a showroom, training place and service center for Decent in the UK.

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