La Pavoni + PID = better temperature control? - Page 8

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ANeat
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#71: Post by ANeat »

Ray great info and very nice work.

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.

Or to put it another way, is the factory pressure relief way of controlling temp really that bad??

Pull a shot the way you would in the past just noting what the temp is reading.
LMWDP #332

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RayJohns (original poster)
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#72: Post by RayJohns (original poster) replying to ANeat »

Yeah, that's a good idea. I'll see if I can rig it up with the PID controller only monitoring the temperature and then run it like I normally would for a shot and see what sort of temperature fluctuations there are. Great idea. I may see about doing that later tonight or tomorrow.

[EDIT: making that video for ya now!]

Ray

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RayJohns (original poster)
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#73: Post by RayJohns (original poster) »

Here's the video I made this morning, which shows the initial test run of the PID controller on the La Pavoni. Basically, I just rigged everything up and let the PID controller go through its auto tuning function. Once it was complete, then I watched as it regulated the temperature for a while. I haven't really dialed in what temperature works well for espresso. I was mainly just wanting to see if things worked and if the RTD sensor was providing the proper feedback.

The video is sort of long (25 minutes), but it's interesting to see how everything functions. The auto tuning took nearly 10 minutes, but I cut the video off while most of that was taking place.

Anyway, it's pretty cool to see the PID controller doing its thing and maintaining the boiler temperature in the La Pavoni.
Next up, I need to draw out the wiring schematic for the OEM / two stage switch. I want to wire things so that "II" controls the steaming (outside of the PID controller) and then "I" is controlled by the PID controller via the 1000W heating element. This will allow me to bring the machine up to temperature quickly, using full power of the "II" setting (outside of the PID controller and SSR) and then once it's up to temp, I can turn it back over to "I" and hand things over to the PID controller as far as maintaining the target temperature for pulling shots.

More on that later. For now, hope everyone enjoys the video.

Ray

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RayJohns (original poster)
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#74: Post by RayJohns (original poster) »

I installed the adapter that Eric sent, while making the above mentioned video for Adam. Here are a couple of quick photos. I just threw some copper washers under it, but they seem to seal okay.

Worked like a charm!


Looking good with the new gauge!


Eric's adapter

Thanks again Eric, for sending the adapter out.

Ray

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RayJohns (original poster)
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#75: Post by RayJohns (original poster) »

A couple more photos:

I added a quick and dirty heat sink to the SSR, just as some added protection for the electronics. During warm up, it was reaching maybe 90 degrees F, so I figured I would slap some aluminum on there.

I had this piece of U channel looking aluminum laying around and it was just screaming "bolt me to the SSR". It came from the inside of an HP power supply that blew up the other day (from my girlfriend's laptop). She's been watching old Mexican soap operas, non-stop, on YouTube and I guess the power supply in her laptop just couldn't take it any longer. haha :-)

Anyway, I drilled a couple of holes in it and used some ceramic thermal paste for installation.

We can all breath a little easier now...


Drilled on the drill press real quick


I had some ceramic thermal paste laying around from working on my Laptop's CPU


The back of the SSR, with the thermal paste applied


Here she is all bolted down



Jules: We're gonna be like three little Fonzies here. And what's Fonzie like? Come on Yolanda what's Fonzie like?
Yolanda: Cool?
Jules: What?
Yolanda: He's cool.
Jules: Correctamundo. And that's what we're gonna be. We're gonna be cool.

:)

Ray

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jknotzke
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#76: Post by jknotzke »

You know what, that was actually really exciting !

You might want to think about getting a job doing play by play for ESPN. ;-)

But seriously, that was really informative. Thanks so much for doing that.

I do have one basic question.. The goal of an SSD is to convert high volts into lower volts and back ? I assume the PID accepts a certain voltage that is much lower then what the heating element wants.. Is this correct ?

J

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ANeat
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#77: Post by ANeat »

J the SSR is just a solid state relay, just like a switch but no moving parts. Anyway the temp controller has a low voltage/amperage set of contacts that can handle turning the relay on and off.

The high voltage for the heating elements just passes thru the relay.


Just like you were sitting there watching the thermometer, and turning the heat on/off as the temp flutuates.


If you get into real fancy temp controllers they will actually be able to vary the % of heat instead of just on/off.

But really Rays setup is working very well, 1/2% or so of deviation.

Im curious to see how the temp that is measured at the bottom of the boiler will relate to getting a proper shot. Should be fun to experiment with
LMWDP #332

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RayJohns (original poster)
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#78: Post by RayJohns (original poster) »

jknotzke wrote:You know what, that was actually really exciting !

You might want to think about getting a job doing play by play for ESPN. ;-)

But seriously, that was really informative. Thanks so much for doing that.

I do have one basic question.. The goal of an SSD is to convert high volts into lower volts and back ? I assume the PID accepts a certain voltage that is much lower then what the heating element wants.. Is this correct ?

J
haha.. thanks!

On the SSR, its function is to switch the circuit on and off. In this case, the circuit is power going to the 1000W La Pavoni heating element inside the boiler.

The PID controller can switch up to a 3 amp circuit itself, but that places more of a load on the relay (i.e. contacts) of the PID controller. Switching a higher amp circuit (2 or 3 amps) generates sparks on the contacts. Also, it takes time to physically open/close the relay.

With the solid state relay, the PID controller only uses about 30 or 40 volts (DC) to send a signal to the SSR which says "okay, we want you to let power through". The relay is designed to switch up to 100 amps (so the 8 or 10 amps drawn by the La Pavoni heating element is just a fraction of what it's rated for). This takes a lot of stress off the PID controller and also allows for a little faster switching rate (since the SSR can switch the circuit on faster than the PID controller's internal relay - at least that's how I understand it).

You can really just think of the SSR as a very tough on/off switch, which is controlled by a very relatively small DC signal coming from the PID controller. Its use allows the PID to be a controller and the SSR to be a relay (as opposed to forcing the PID controller to serve double duty as a controller and relay).

Also, in my configuration (using the 1000W heating element), it draws more current than the internal relay of the PID controller can handle. My original idea was to use the PID controller to switch the lower (200W) heating element of the La Pavoni, but the problem is that the 200W heating element doesn't really have the horsepower to generate enough heat fast enough. And that power is needed, since the PID controller wants to just cycle the heating element on and off very briefly, in order to fine tune. If you tried to use the lower 200W heating element, it would sort of end up taking too long to inject the required amount of heat per each cycle.

Anyway, that's sort of the deal there.

Glad you enjoyed the video. I'm working on another one (per Adam's request above) right now, which you might also enjoy - it's a bit long, but I think it's very informative.

Ray

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jknotzke
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#79: Post by jknotzke »

Fantastic. Thanks so much for that.. I adore threads like this. These machines are complex but not complex enough to not be able to understand and videos and threads like yours really prove that.

You have an excellent style in explaining things which makes it even that much more fun to watch.. I really wanted to see that PID work!

Cool stuff.

J

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RayJohns (original poster)
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#80: Post by RayJohns (original poster) replying to jknotzke »

Thanks a lot :-)

I'm just finishing up another video (which shows the PID controller monitoring the La Pavoni as it operates on its switch "I" setting). It turned out pretty interesting and I think it will be helpful to those just getting started on the older La Pavonis. The video is in post production right now (I'm writing it out to an mpeg file as we speak). As soon as it's done, I'll start the upload to YouTube and then post the link later today/night.

Ray