Decent Espresso v1.1 shipping! - Page 7

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RyanP

Postby RyanP » Feb 16, 2019, 1:06 pm

pcrussell50 wrote:What does a soupy puck portend about shot quality? Does it harm taste in the cup? My intuition tells me it wouldn't harm a thing. Or is it mostly just an aesthetic irritant?


It's more just a PIA. A small one, but a pain, nonetheless.

Iowa_Boy

Postby Iowa_Boy » Feb 16, 2019, 1:07 pm

pcrussell50 wrote:What does a soupy puck portend about shot quality? Does it harm taste in the cup? My intuition tells me it wouldn't harm a thing. Or is it mostly just an aesthetic irritant?

Going all the way back to page one of this thread, it's interesting that the group head heater is 100W, just like the group head heater in the Breville Dual Boiler. Ever since the BDB came out with that feature in 2011, I have wondered about the power of it, and whether there was any point or value in having one more powerful than 100W. I consider it encouraging that Decent also uses a 100W final heater. Makes me wonder in what other ways the water temp control algorithms are similar. If you were wanting say, 200degF brew temperature, what would the water temp be just before it hits the group heater? IOW, how many degF does the group heater add? Does the DE sensor suite tell us that? Or is that DE Pro territory?

-Peter


Mostly just curious regarding the puck. With my Breville Dual Boiler, I don't need a knock box. After the shot, just a flick of the wrist above the trash can and the coffee puck easily dislodges from the portafilter and into the garbage can. I quickly rinse the portafilter and I'm ready for another shot. A soupy puck would make much more of a mess with this workflow if it didn't cleanly come out. Still planning to get a Decent machine this year, so I agree it's just a minor workflow question.

JonF

Postby JonF » Feb 16, 2019, 1:32 pm

When I moved out into the country, my workflow changed to reduce the amount of grounds going down the sink. I actually put a paper towel on the tamping pad. After brewing I dump the grounds onto the pad. Then I bundle them up and use the top to quickly wipe off the shower screen before I toss them. A side benefit is that the paper collects errant grounds as I grind into the portafilter. I occasionally get soupy pucks, but the paper soaks the excess water.

pcrussell50

Postby pcrussell50 » Feb 16, 2019, 2:14 pm

Iowa_Boy wrote:Mostly just curious regarding the puck. With my Breville Dual Boiler, I don't need a knock box. After the shot, just a flick of the wrist above the trash can and the coffee puck easily dislodges from the portafilter and into the garbage can. I quickly rinse the portafilter and I'm ready for another shot. A soupy puck would make much more of a mess with this workflow if it didn't cleanly come out. Still planning to get a Decent machine this year, so I agree it's just a minor workflow question.


One thing I've never been too fond of, is dinky "home-sized" boutique knock boxes that require emptying so often that it makes them seem like a toy, so home baristas can play pretend shop barista, or so it looks to to me. Not to be too much of a shill to Breville, but the Breville knock box is usefully sized, without being obnoxious, and tastefully styled.

I wonder if you have the older -900, tapered baskets? They are a dream for knocking out. I use them in conjunction with VSTs depending on the bean. They've hard to find, though. :(

-Peter
LMWDP #553

JayBeck

Postby JayBeck » Feb 16, 2019, 2:27 pm

pcrussell50 wrote:What does a soupy puck portend about shot quality? Does it harm taste in the cup? My intuition tells me it wouldn't harm a thing. Or is it mostly just an aesthetic irritant?

Going all the way back to page one of this thread, it's interesting that the group head heater is 100W, just like the group head heater in the Breville Dual Boiler. Ever since the BDB came out with that feature in 2011, I have wondered about the power of it, and whether there was any point or value in having one more powerful than 100W. I consider it encouraging that Decent also uses a 100W final heater. Makes me wonder in what other ways the water temp control algorithms are similar. If you were wanting say, 200degF brew temperature, what would the water temp be just before it hits the group heater? IOW, how many degF does the group heater add? Does the DE sensor suite tell us that? Or is that DE Pro territory?

-Peter


Answer to first question: Has nothing to do with the espresso. It is purely an aesthetic / workflow pro/con. If you updose a little the puck will be drier but it is still airey. The reason for this is that the machine doesn't back flush; it forward flushes. These action doesn't suck the puck up like most machines, it just lets excess water out through the flush valve so sometimes water can sit on top. It also doesn't suck the puck up AT ALL so it isn't compressed like other machines do when they release pressure. I've actually found that sometimes the more watery pucks knock out 'cleaner' than the drier ones.

Second question: Someone from Decent would have to respond on the comment of what exactly the grouphead heater does (John, Ben, or Ray). I can tell you that the machine is actively mixing hot and cold water to achieve the final temp at the puck based upon what the multiple temp sensors are telling the machine during the entire shot. This is actual temperature profiling, in real time, based on what's happening at the puck (heat loss from grounds, portafilter, flow rate, etc).

As I understand it, the group heater is only on when idle unless the flow rate is very low (less than 1ml/s on pouring phase of a shot). When the machine shipped, the group heater was off during a shot and the water mixing technology fully controlled shot temperature. These algorithms were designed for standard flow rates (1-2.5ml/s). As users have been gravitating towards shots closer to 0.5ml/s, many noticed that temp was dropping per the vast amount of sensors sending data via graphs. Ray (lead firmware guy) said that the reason for this is due what I said last sentence (his algorithms, which are very complex, don't account for such low flow rates). To address this, he recently added firmware that kicks on this grouphead heater during low flow shots (less than 1ml/s). Based on user reports, this has made temp accuracy better.

So to your point, I think the answer is somewhere in between. The grouphead heater on the DE1 is PID controlled and sets the metal temp to the target temp. Once the shot starts, then it's either on or off/pulsing depending on what I just said last paragraph. As I understand the BDB, the grouphead heater is NOT PID controlled and is likely set up to turn on/off based on firmware Breville developed during R&D of the machine.

pcrussell50

Postby pcrussell50 » Feb 16, 2019, 2:49 pm

JayBeck wrote:

So to your point, I think the answer is somewhere in between. The grouphead heater on the DE1 is PID controlled and sets the metal temp to the target temp. Once the shot starts, then it's either on or off/pulsing depending on what I just said last paragraph. As I understand the BDB, the grouphead heater is NOT PID controlled and is likely set up to turn on/off based on firmware Breville developed during R&D of the machine.


Actually, this is a common misunderstanding. The BDB's two PID controlled heaters are one for the brew boiler and one for the group head.

From Mark Prince's intro when it first came out:
And here's where Breville's next trick is. It features not one, but two PID controllers. One is working on the brew boiler, and the second one isn't where you'd expect it: it is on the grouphead, not the steam boiler.


http://coffeegeek.com/proreviews/firstlook/brevilledualboiler/details

And if you think about it why would you need/want one for a steam boiler anyway? Of what value is sub-one degree stability in a steam boiler?

-Peter
LMWDP #553

MrEd

Postby MrEd » Feb 16, 2019, 5:20 pm

Recently Ray Heasman from Decent Espresso posted in their internal users forum details of how water temperature is controlled in the DE1. I thought it would be of interest to people here, so I got permission from him to excerpt from it.

This diagram of the water flow path and where all the sensors are will hopefully make the following discussion a bit easier to understand. There are slight differences in the physical locations of the group head sensors (P6, P10, P12) between v1.0 and v1.1, but they are functionally equivalent.
Image

My additions to Ray's text are denoted by [].

The "water temp" is actually the temperature of the sensor (P12) that measures the water as it enters the brass part of the group head.

Deep dive into how a shot is poured

Preheat-A
When an espresso is requested, the machine powers the water heater thermocoil at 100% power, and starts pumping water slowly through the heater and manifold, and back into the water tank via the group and return valves. It does this until the heater temperature (P7) shoots past the required temperature. (It keeps on going, too, due to thermal lag in the heater metal).

Preheat-B
Then, the machine switches to another phase where it starts water mixing to reach a target temperature (P8) just a little bit higher than the target, and routes that water through the group valve and return valve. This is to pre-heat the manifold and group valve.

This is why we have the bizarre configuration where a three-way valve leads into a two-way valve that returns to the tank. We found that not preheating the 3-way valve to the group was worth up to a 5°C drop (that lasted half the shot) if the valve was cold. This pretty much ruined the first shot of the day, and meant that the temperature of a shot was dependent on how long the valve had had to cool.

Pour
Then, we switch to the "real" start of the shot. The mix water temperature (P8) is intentionally a little high. Water in the tubes between the manifold and group enters the group, and it's usually a little cool. There is a stretch of PTFE tubing from the group back to the main manifold that is the only part of the machine not under heat control. If that tube cools down, then the water in it will be a bit cooler. But, there is supposed to be a layer of insulation inside the group head so that the variation is not too bad, and the group is itself heated to deal with little excursions like this in the inlet temperature. The group itself will heat or cool the water for a few seconds, before the water temp starts overwhelming the metal temp (P10).

At this point, the machine starts monitoring the shower head temperature (P6), and adjusts the mix temperature (P8) to heat or cool the water heading to the group, to try to make up for any temperature deviation. However, it does limit the range of output temperatures, as deviating the water temperature too much affects the flavour.

Then, this water wends its way from the mixer to the main manifold to the group. The tubes used are quite thin, but at low flow rates this can take a while. As a result, the temperature control PIDs all use the flow rate to adjust their speed. If the flow rate is super slow, it can take tens of seconds for the mixed water to hit the puck, and a PID would go into oscillation if it tried to adjust temperatures faster than that.

An ideal water path would have no length. We'd mix water directly in the group, and the mixed water would directly enter the basket a fraction of a second later. For many reasons, we couldn't do this for the current machine. I live in hope that one day we can do better.

For very slow flow rates, the group heater is actually a pretty good way to control the temperature [This is what JayBeck was referencing above, and the group has a 250W, not a 100W, heater]. As the flow rates increase, we end up in a situation where the water mixer and group controller can fight each other, and I haven't found a way around this yet. This is one of the reasons why the group heater is turned off for faster shots.

How the group temperature is measured/controlled

The DE1 has temperature sensors coming out of its ears, and there are three sensors in the group, alone. One measures the metal temperature, one measures the water inlet temperature, and one measures the temperature at the puck. I call these the "metal" (P10), "inlet" (P12) and "shower head" (P6) sensors.

It is not unusual for these sensors to report values that a very different from each other. The shower sensor can be 20°C below the metal temperature, if it's picking up the cool air beneath the shower screen. On the other hand, if there is some residual water sitting above the screen, bubbling down from the inlet chamber, it can be a degree or so away from the metal temperature, as there is water giving it contact to the brass, but no water in contact with the shower screen.

The metal temperature can be surprisingly low during an initial heat-up period, because heat is being leached into the chassis and the group head carrier (the tow hitch shaped thing). In this case, the inlet sensor is actually the best guess of what the final water temperature would be.

That's our priority: get the group to a temperature where the water temperature entering the puck is near our target.

There is also a temperature difference between the top and bottom of the group. With insulation in the group, the top of the group is usually a bit hotter than the bottom. This is because most of the heat is escaping to the air under the group and into any portafilter connected. With no insulation in the group cover, the middle of the group was hotter than either the top or bottom.

What I settled on, is that the group head controller (when not doing a shot), actually looks at the maximum of all three sensors, and controls that. In tests, if I suddenly sent water through the group, the highest temperature sensor recorded was the best predictor of the water temperature.

When the shot starts, the group controller is turned off unless the flow is really slow.

Shot temperature control

During the shot, there are multiple PIDs. One PID controls the water mixer to meet its target temperature (which controls other PIDs for each pump). Another looks at the inlet sensor and controls the water mixer target temperature. Another looks at the shower sensor and controls the setpoint for the inlet sensor PID. Each PID looks at the flow and takes flow delays into account.

Thoughts

I've done thousands of shots through our group heads, watching the internal sensors and the output from a Scace. I am comfortable that we provide pretty good temperature control for reasonable flow rates, and that what you see in the app is representative of reality. Of course, all four temperature sensors in the middle of such a test shot disagree with each other a bit, because none of this is actually simple. During manufacture, we adjust the global temperature calibration so that the average temperature on the Scace for the second half a the shot matches the target temperature for the shot.

I have 14 temperature sensors, and none of them agree on anything. It's very humbling. :-)

In general, if the group temperature is seriously wrong, then a shot will take well over ten seconds to compensate for that. If the group temperature is right, then it will save us from temporary water temperature deviations.
★★ Quite Helpful

Fluffeepuff

Postby Fluffeepuff » Feb 17, 2019, 1:46 am

MrEd wrote:Recently Ray Heasman from Decent Espresso posted in their internal users forum details of how water temperature is controlled in the DE1. I thought it would be of interest to people here, so I got permission from him to excerpt from it.


Thank you for sharing.. this was very interesting to read.
<*>---<

Davidm

Postby Davidm » Feb 17, 2019, 10:43 pm

I just read this again (first time in the basecamp forum). I hope this also helps others understand why Decent owners are dedicated and sometimes might sound like diehards. It is hard not to be when you have such a close connection to the people that make the machines. Also, I don't think that the Decent team sleeps (just my opinion). Their transparency is refreshing as well.

I have had my machine a little over six months now. I just added a skale so that I can measure flow rate into the cup and stop at a specified weight. I still watch the chart, the first drips out the bottomless portafilter, and the chart of the shot developing. I didn't realize that the process of making espresso is as satisfying as the results of the process.

JayBeck

Postby JayBeck » replying to Davidm » Feb 17, 2019, 11:05 pm

+1