La Pavoni + PID = better temperature control? - Page 9

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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ANeat

#81: Post by ANeat » Apr 20, 2011, 11:05 pm

Just caught the new video, pretty interesting results. Looks like with a pressure gauge you could "surf" from that. I thought the pressure bleed off would be a little more definitive, possibly being able to go by ear on the steam release.

I can certainly see where some user experience really pays off

So I assume youre still going ahead with the manual pump experiment as well? Are you just looking to generate the pressure to pre-infuse but at a lower temp?


I really had no idea the temp would be so high at the boiler. Ive always read that such high temps were bad but obviously folks have gotten good results for years and years.

Of course where the water hits the coffee is where it counts....right?
LMWDP #332

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RayJohns

#82: Post by RayJohns » Apr 21, 2011, 5:18 am

ANeat wrote:Of course where the water hits the coffee is where it counts....right?
Yeah, I was sort of surprised by the temperatures involved also (I'm assuming you are talking about the new video which I uploaded to YouTube - the one you suggested where the PID only monitors the temp?) If not, I'm about to post the link below.

But yes, it's interesting that the boiler temperature is higher and then there is such a temperature drop when pulling the shot. My original thinking was that I would run the machine at maybe around 205 degrees (in the boiler) and then need a hand pump to pressurize it. However, now, I'm starting to wonder if maybe the answer is to run the boiler at 220 to 235 and hunt around in that area for where the shots taste good.

Yesterday, I set the temp down around 220 degrees (as I recall) and still had about 5 PSI in the boiler (just enough pressure for pulling shots). I used an Italian Roast and the shot was very good. In fact, my gut feeling was that it might have been improved by a little higher heat, so that was interesting to note (although I didn't do any fine tuning, so I could be mistaken in my assumption).

With the PID controller, I think I should be able to fine tune things very accurately. Perhaps to where there is just ever so slight a balance between having low heat and just enough pressure to pull a shot. It's possible this might make the whole hand pump issue moot. However, it's still too early to say for sure. Also, I did notice that at the lower pressure, the group head doesn't really fill up as forcefully as one would probably like. Additionally, since I was only pulling one or two shots - here and there - the group head might not have really been up to its normal operating temperature. As such, the temperature drop I have been witnessing recently might tend to vanish as the group head increases in temperature. It's hard to say, but I think it's possible. This also speaks to why the E61 group head uses so much brass and also water recirculation in order to help pin its temperature.

Anyway, at the end of the day, I'm not trying to turn the La Pavoni into a $15K espresso machine. I'm only trying to provide some increased level of temperature control - which will help settle down one of the machine's more troublesome variables (i.e. heat). With the PID controller, I'm able to set the temperature and forget about it (to a large degree). This allows me to focus on stuff like the tamp and grind and then judge how the espresso comes out (without having to wonder if one shot was good because the water was a little hotter or a little cooler at the exact moment I pulled the shot).

With the PID controller, I think I'll have a lot more luck dialing in espresso beans. Even with only a little testing, I already really like how everything functions. As mentioned, I haven't really had a chance to play around too much with different temperature settings, but I am liking the basic overall setup.

In using the machine now, I am quickly starting to think that having some sort of temperature gauge incorporated directly into the group head's water chamber would be nice. I'm not real keen on the idea of drilling the group head itself, but I would like to figure out some slick method for seeing what the water temperature above the puck (just prior to pulling a shot) ends up at :-)

Ray

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RayJohns

#83: Post by RayJohns » Apr 21, 2011, 5:25 am

ANeat wrote:One thing Im wondering. If you dont mind, I was curious to see how much temperature drift was in the factory setup. IE, run it the way you have in the past, but with the temp sensor just reading the temp.

Pull a shot the way you would in the past just noting what the temp is reading.
Ask and you shall receive! :-)
I made the above video above at Adam's suggestion, which was a really great idea: run the La Pavoni as you normally would, but use the PID controller to monitor what's going on with the boiler temperature.

The video is a bit long, but for anyone with a La Pavoni (or just learning how to pull shots on one of the older machines), I think it's enlightening as far as how temperature relates to pressure, etc. The one caveat here is that I do have a modified pressure relief valve, so my pressure setting is not going to match a totally stock La Pavoni exactly. Nevertheless, I think it's fairly safe to guess that the stock La Pavoni pressure is probably around 1 BAR or so from the factory (perhaps someone has measured it on their Pre-Millenum machine and can chime in?).

Anyway, hope everyone enjoys the video! :-)

Ray

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RayJohns

#84: Post by RayJohns » Apr 21, 2011, 9:58 am

I drew up the wiring diagram / schematic for the La Pavoni, tonight.

It appears below:

Image

As you can see, the wiring configuration utilizes the original factory, two stage switch. When power is applied (via the on/off switch), the PID controller is powered on.

When the high / low switch is in the high (II) setting, then the SSR is bypassed and the La Pavoni's 1000W heating element is powered on directly. During this mode, the machine will quickly come up to full temperature for the purposes of steaming milk. At the same time, since the PID controller will continue to receive power, it will display the water temperature inside the boiler (even though it will not be regulating the temperature). Thanks definitely should go to Adam for this feature, for without his suggestion above, I probably would not have thought to wire the unit up in this manner (i.e. as a temperature display only).

When the high / low switch is in the low (I) setting, then control of the 1000W heating element is handed back over to the PID Controller (and thus switched on/off via the 100A solid state relay). In this mode, the PID controller will regulate the La Pavoni's boiler temperature to the SV "set value" parameter (i.e. the target temperature you program in - either in degrees F or C) so that you can extract espresso.

Later this morning, I will probably wire the machine up in this manner (with the original switch) and test it out a bit.

Ray

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RayJohns

#85: Post by RayJohns » Apr 21, 2011, 2:16 pm

I just finished testing the machine with the new wiring setup... man oh man, amazing.

It's up and running within a couple of minutes and ready to pull shots. You just flip it to the "II" setting, it comes up to temp and then you flip it down to "I" and hand things over to the PID controller. I have the PID controller set to 230 degrees F and it keeps the machine at about 6 PSI in the boiler. It's so quiet on the counter that you forget it's even on; the PID controller keeps the temperature within about 1/2 a degree or so.

I also did a test to see how long it takes to go from 230 degrees to being ready to steam milk. If it's coasting along on the PID and you flip it to the high "II" setting, it builds up enough steam to start frothing milk in about 25 to 30 seconds. Within 45 seconds, it's over 250 degrees and putting out steam like nobody's business.

So I think this will work really well as far as making lattes, or any drink that involves steaming milk. I'm still refining my milk frothing technique, but the machine definitely seems to steam well - and I've noticed the adjustable pressure regulator is really handy, as far as adjusting the upper limit of the boiler pressure, when the machine is on the "II" setting and maxing out.

As far as steaming milk, that's still a work in progress for me. I'm currently using a single tip and steaming the milk to between 130 and 140 degrees (this is the temp reached after I shut the steam wand down and it coasts a bit, btw). Based on the limited testing I have done with steaming milk, I'm starting to think that my ideal target temp is gonna be right around 135 degrees (but I'm still testing that out).

The nicest part, since it only takes about 25 or 30 seconds to switch modes and come up to steaming temperature - which is about how long a shot takes - is that you can switch the machine to the "II" setting right as you begin pulling a shot (right after you lift the handle and bring water into the group head). Using this approach, by the time you finish pulling the shot, the boiler is already up to temp and ready to steam milk.

I'm going to do some more testing later on, but so far it's looking pretty good over here. Even without really dialing in the exact/best temperature, the shots have been coming out much more consistent (and I think most of my beans in the house are probably pushing their shelf life also). I'm also thinking there is probably no major need to install a manual hand pump. With the PID controller in the 225 to 230 range, there's just enough pressure in the boiler (around 5 PSI or so) to push the water into the group head. Also, with the PID controller keeping the boiler temperature under control, the machine doesn't over heat and become super hot, which is nice.

I still need to fine tune what temperature to run everything at, but today I pulled some water through the group head (without the portafilter installed) and by the time it hit the shot glass, the water temperature was just under the 180 degrees F. I believe that was with the PID controller set to 230 (I'll do some more testing on that soon).

In other news...

I noticed the lamp on my on/off switch doesn't seem to work properly. As far as I can see, it's supposed to light up when you turn the switch on. However, it appears to be defective, in that it only lights up if you push down hard on the on/off part of the switch. I tried cleaning the contacts by running soap & water through the switch (as well as carb cleaner) and then blowing it out with the air compressor, but no luck. I'm thinking the switch may just have a faulty contact inside. The switch appears to be sealed, so I may need to order a replacement at some point.

I'm also still debating on whether or not to install the PID controller inside the base of La Pavoni (so that the LED screen is where the logo used to be). Now that the machine is under some sort of temperature control, it seems that the air temp under there doesn't really get too hot. So we'll see. I also need to figure out where to locate the SSR. Since it only functions now to trim out the temperature, I don't think over heating will be much of a concern on the relay. Nevertheless, I may see about adding a little sheet of aluminum plate (for the SSR to bolt to), so that at least the SSR has some means to dissipate any heat that does build up.

That's about it for now. I'm going to run the machine "on the bench" (i.e. with all the wires hanging out, etc.) for a while and see how things go. So far, it's great though - the PID controller really brings out the best in the La Pavoni. Next up, I think I need to buy some fresh beans, since most everything in the house is probably going stale (given that the La Pavoni was out of commission for nearly a month!).

Ray

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drgary
Team HB

#86: Post by drgary » Apr 21, 2011, 5:53 pm

Hi Ray,

Thought I'd chime in to your fascinating experiment by providing feedback from using my Pavoni Millennium, which was redesigned for better temperature regulation. I haven't found a definitive description on this site of the design changes made to the Millennium Pavonis, but that may just be because I haven't found it. Anyway, back to your thread. I'll quote you, then comment:

"I did notice that at the lower pressure, the group head doesn't really fill up as forcefully as one would probably like."

I notice it can take awhile for the pre-infusion to occur, which suggests it's not at high pressure. I don't have a manometer attached so can't give you a read-out. I achieve additional temperature control by cooling the portafilter. With your PID, you may not need to do that but may be adjusting slightly in the other direction by powering up for steam for 30 seconds. I don't need to power up for steam. It's sufficiently there right away. In other words, I wonder if these machines are designed to maintain ideal temperature at the group and for steaming at the same time? Maybe, maybe not, and with your PID you'll be able to fine-tune it enough to determine that. Of course, your machine probably disperses heat differently at the group than a Millennium model.

"...the E61 group head uses so much brass and also water recirculation in order to help pin its temperature."

My Millennium machine is not quite stock but has had the plastic piston replaced with a brass one, something Christopher Cara suggested, and he does know his Pavonis. This may be a reason why in some other threads, other writers had difficulty believing the temperature control on mine is so easy. Temperature control on mine may be eased further by my not using a bottomless portafilter, so when I cool the PF under water, there may be an extra cooling factor.

"This allows me to focus on stuff like the tamp and grind and then judge how the espresso comes out (without having to wonder if one shot was good because the water was a little hotter or a little cooler at the exact moment I pulled the shot)."

I think those adjustments make a huge difference in the extraction, which is really what you're working with, as does length of time allowed for pre-infusion. In other words, after you've done the re-engineering of temperature regulating your machine, I'll be interested to see how much control you discover by using barista skills.

"With the PID controller, I think I should be able to fine tune things very accurately. Perhaps to where there is just ever so slight a balance between having low heat and just enough pressure to pull a shot. It's possible this might make the whole hand pump issue moot."

My hunch is you won't need the hand pump. But as you wrote, it's too early to say. My hunch follows reasoning that both your and my machines can pull a balanced shot and then quickly go to steaming, suggesting a balance between temperature and pressure that's fairly good in the stock design.

"I think I need to buy some fresh beans, since most everything in the house is probably going stale."

Let them rest until they're at peak, then freeze them, airtight, in a cold freezer. Another thread on this site with expert, blind tasting showed this improves the coffee! See: Freezing Espresso Coffee, Part Two

Nice experiment. Many of us are watching!
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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RayJohns

#87: Post by RayJohns » Apr 22, 2011, 6:40 am

drgary wrote: Let them rest until they're at peak, then freeze them, airtight, in a cold freezer. Another thread on this site with expert, blind tasting showed this improves the coffee! See: Freezing Espresso Coffee, Part Two

Nice experiment. Many of us are watching!
Thanks for the comment Gary!

I've noticed my coffee seems to improve after I have had it (and opened it) for a bit. I need to find a coffee I like more. Some of the beans I have been using produce a very sweet espresso, but I'm after something which has more of a smooth coffee flavor, but without quite as much sugary flavors. I had a very good espresso a while back at the local California pizza kitchen (of all places), so I may stop in there and ask them. I also had a very good espresso on Catalina Island some months ago and I believe they were using LaVazza beans (although I'm not sure which one).

Anyway, I'm going to order up some fresh beans soon here I think and see if I can find something with a more mild coffee flavor. I'm trying to find something more along the lines of how coffee ice cream tastes, but in espresso form.

This morning, when I woke up, I turned the machine on and brought it up to temperature (230). I watched it for a while and the PID controller kept it within less than 1/2 a degree of the set temperature. I'm actually going to go pull a shot or two here in a minute I think.

So far so good :)

Ray

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RayJohns

#88: Post by RayJohns » Apr 22, 2011, 6:51 am

drgary wrote: With your PID, you may not need to do that but may be adjusting slightly in the other direction by powering up for steam for 30 seconds. I don't need to power up for steam. It's sufficiently there right away. In other words, I wonder if these machines are designed to maintain ideal temperature at the group and for steaming at the same time? Maybe, maybe not, and with your PID you'll be able to fine-tune it enough to determine that. Of course, your machine probably disperses heat differently at the group than a Millennium model.
I think there is some validity to what you are suggesting there, as far as the temperature drop between the boiler and the group head resulting in the water being about the proper temperature once it reaches the coffee. Before I set about adding the PID controller, I took some measurements and I do seem to recall that the water coming out of the group head seemed like it was around a pretty good temperature (between 180 to 190 or so). This leads me to believe that when the La Pavoni is fired up on the "I" setting, it has some steam available and also is approximately the correct temperature. I suspect that La Pavoni calibrated the pressure relief valve in such a way as to try to hold the boiler temperature near what they felt would be a good temperature based on water cooling as it went into the group head. This also speaks to why people run into problems with the machine over heating (and thus cool the group head back down with a cold, wet towel). That's not something I have ever tried, but it follow that it would help.

I was actually thinking about making a chart of pressure vs. temperature for my machine (and as a reference to other La Pavoni owners).

Having the PID controller on the machine changes the ball game a little bit for me. Since the machine no longer really over heats (and I am no longer having to temperature surf it by turning it on and off), I think I'm going to have to relearn how to use it a bit. Like I say, I also need to buy some fresh coffee too, but having the PID controller on there is a big step in the right direction. The few shots I have pulled since running it on the PID have been very good (and that's without much dialing in). It seems like having the PID controller keeping the temperature in check has removed the "too bitter" shots from the equation. Since putting the machine back together, I haven't had anything which turned out burnt or bitter tasting. If anything, they are a touch sour, which suggests I may be running the machine a little on the cool side.

So we'll see how it goes over the next few weeks here. I may shop around for some different beans to try and/or call down to CPK and see if I can find out what brand of beans they are using for their espresso.

Ray

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RayJohns

#89: Post by RayJohns » Apr 22, 2011, 7:41 am

I checked the temperature of the water coming out of the group head just now...

After pulling a couple of shots through the machine and with the PID controller set to 230 degrees F, I pulled the remaining water in the boiler through the group head and into a measuring cup. The temperature (with the instant read thermometer) was a solid 195.

I think I'm going to back the PID controller down to 228 or so for a while and see what effect that has on the water temperature that is reaching the portafilter.

Ray

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RayJohns

#90: Post by RayJohns » Apr 22, 2011, 8:52 am

I realized this thread maybe doesn't have enough photos (just kidding, har har).. so here are a few more:

Image
Testing out the new wiring configuration with the OEM switch

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The M12 x 1.00 die arrived today. This will come in handy when fabricating up the final gauge adapter for the machine (although I will say that the one Eric sent is working great!).

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And this morning's Long Black - pulled at 230 degrees on the La Pavoni :-)

Ray