decent_espresso wrote:A year ago, when I spoke to Rao about whether temperature profiling might be desireable, he articulated more or less your point, that the only way he saw it as useful was with a decreasing temp curve.

I then argued for an increasing temp curve, on the assumption that as the shot progresses it is harder to extract the remaining coffee material, and thus a higher temperature would be needed. He conceded that was a valid theory.

The DE1+ can do either, as well as letting you choose between a temperature curve that is water-temperature-only, versus an automatic water temperature but with a rising (or falling) temperature-at-the-puck goal.

Here's where you can do this in the Advanced shot editor that I'm currently working on.

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I do agree with Scott Rao. Probably a rising temp is not desirable, but hey, having the option is great. I am happy I finally pre-ordered.

decent_espresso wrote:We've upgraded to a high end "pick and place" machine to make our own circuit boards for our espresso machine. We like the control it gives us, to know that every part on the board is the one we chose. It lets us make short runs and also create small circuits for specific tasks (such as for a testing station) . Even better, the machine pays for itself with the first 1000 espresso machines we make, bringing the per-espresso-machine board cost down from $90 to $50.

We're calling this machine "Peter", as in "Peter Piper picked a shed load of components almost 500 and made them into PCB boards".

Here's a picture of a Very Happy Jeffrey with his new toy. You can see the puny old machine we previously used, to its right.

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Everything that you can produce in home, given the attention to detail that you guys are putting in, will be better than outsourcing. I bet you QC will be better, and even you have the possibility of varying design as much as you can!

Here's to Decent running out of capacity on that workhorse. And upgrading to this (no longer a "horse"):

Like andreugv1 I'm also on the fence between normal or Pro. Sounds like my usage level would put me in normal territory, especially if the pump is the likely limiting factor and replacement pumps are reasonably inexpensive, available, and easy to install. That said, I may eventually (though not initially) want to plumb the machine in. Is this possible?

The PRO is the only model we're offering with the extra circuit board logic to support plumbing, so the other models are not upgradable to plumbable, sorry!

andreugv1 wrote:Everything that you can produce in home, given the attention to detail that you guys are putting in, will be better than outsourcing. I bet you QC will be better, and even you have the possibility of varying design as much as you can!

On monday we had these circuit boards ready for testing and "implantation". Quick turn around, and if we want to make any changes to the boards, we can.

decent_espresso wrote:On monday we had these circuit boards ready for testing and "implantation". Quick turn around, and if we want to make any changes to the boards, we can.
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SAMS-70? 32bit Cortex M7 w/FPU. Hmmm. That is a powerful chip...

One can do quite a lot with that processor.

Scott and John describe a test of constant flow profiling at http://scottrao.com/blog/decent-demo-in-budapest. After an initial transient, the flow rate is held at 1.5 ml/s. The pressure steadily builds to sustain this flow rate. Scott believes that they got an "extraction in which the puck never compressed," but I am not so sure. The pressure is near 5 bar after about 30 seconds. 5 bar of pressure is about 12 times more pressure than the pressure that is provided by the Decent Espresso 25 pound tamper. I think that is enough to compress the puck. Also, the pressure had not leveled out. If Scott and John had made a longer shot, I think that the pressure would have leveled out when the puck became fully compressed for that particular flow rate. I think that for a fully-compressed puck that the pressure is a quadratic function of flow rate. Let's say that the pressure levels out near 5.5 bar after 45 seconds. For a constant flow of 1.75 ml/s, I think that the pressure will level out near 5.5 x (1.75/1.5)^2 = 7.5 bar, all other things being the same. I think that this relationship between pressure and flow rate is only true in a limited range. I think that it is possible to press the puck so hard that the flow is restricted. Under those circumstances, the relationship between pressure and flow rate will be higher than quadratic. In way of clarification, what I mean by a fully-compressed puck is the compression a puck will reach when the pressure levels out for a particular flow rate. I think that for higher flow rates that the puck will sustain more compression relative to lower flow rates when the pressure levels out and reaches a constant level. The Decent Espresso machine allows us to explore "fully-compressed" pucks for a given flow rate. I am looking forward to getting my DE1+ PRO.

BWA wrote:Scott believes that they got an "extraction in which the puck never compressed," but I am not so sure. The pressure is near 5 bar after about 30 seconds. 5 bar of pressure is about 12 times more pressure than the pressure that is provided by the Decent Espresso 25 pound tamper. I think that is enough to compress the puck. Also, the pressure had not leveled out. If Scott and John had made a longer shot, I think that the pressure would have leveled out when the puck became fully compressed for that particular flow rate.

I think your latter point - that the puck could have been more fully compressed for that flow rate - is really what Scott is getting at. I took his point to be that once the puck has gotten as compressed as it's going to get, you would expect that the pressure needed to maintain a given flow rate would decrease over time, due to puck erosion. But his point (as I take it) is that the puck was still compressing, the pressure thus needed to increase to counter the effect of that compression, and that necessary increase more than offset the effect of the puck erosion.

I just think they went so slow that the preinfusion never ended.

To get a better grasp for this It is useful to use a better grok'ed corollary for flow vs pressure profiles.

Pressure is potential energy - like voltage. There is a potential (pressure) on the puck.
Flow is the current through the puck. It is a result of the pressure across the puck.

(obviously this is interchangeable: for a given puck, a certain pressure will yield a flow. Similarly forcing the flow would mean that the pressure across the puck would be the same pressure as before. Conservation of energy or work in this case).

Flow profiling is controlling "current" (in his case since flow is constant - it is a constant current source).
Pressure profiling is like a voltage source (like a power supply). You control the potential difference.

Slayer is similar to a constant current source (nearly - unfortunately gear pumps have slip and current limiting etc.). Its pressure profile always jumps at the PI end - and always tapers down. For a full pull cycle - that will always happen.

In this case pressure never got a chance to climb. Had he pulled another 50 seconds pressure would have continued - peaked - and then decayed. Stated otherwise - we are seeing the preinfusion half of a very slow graph.

Even if the initial burst did fill the overhead space - it seems to me the flow was only slightly higher than the drip output from the bottom of the basket - so pressure could not rise fast enough.