So right next to Sequim? Don't worry, it's a bit out of my hood.

Ahem, so getting back to the topic...

I see the Alex Duetto II has a PID which controls temperature in each boiler. Not being a big latte guy I'm not sure why you would need to have such precise temperature adjustments in the steam boiler. Wouldn't it make more sense to have the PID control temperature both at the grouphead and at the coffee boiler? Would that lead to better stability?

Is there not a machine that does that?

My Silvano does seem to have pretty good temperature control in the cup, btw. With a simple thermometer, which I have carefully calibrated beforehand, I've verified the temp in the preheated cup is very close to the reading on the PID.

innermusic wrote:Is there not a machine that does that?

There is one in my kitchen

I made a controller that reads up to four sensors (I use only two). The PID algorithm takes both readings into account before deciding how much power should go to the heater. Right now I have the controller inside a Silvia. I plan to install one in my Alexia as soon as I get aroundtoit.

As you might expect, this is a lot better than a single sensor system that only knows the temperature at the top of the boiler. Variations in average shot temperatures are almost completely eliminated, even when ambient conditions change or the machine is "overheated" after steaming.

The nicest unexpected benefit is how much faster the machine warms up. Rather than 45 minutes or more, my Silvia now is temperature stable after 15 minutes from cold start.

Jim

That's what I'm talking about. However, not being inclined to make these mods myself, I'm wondering: which machines come that way?

JimG wrote:As you might expect, this is a lot better than a single sensor system that only knows the temperature at the top of the boiler. Variations in average shot temperatures are almost completely eliminated, even when ambient conditions change or the machine is "overheated" after steaming.

1. Where are the sensors normally located in a single sensor PID system? The boiler, or the grouphead?
2. What semi-commercial machines currently come with both sensors? Seriously, is this not available in machines in the $2000 - $2500 price point?

AFAIK, most SBDU machines have brew sensors on, or near, the top of the boiler.

The QM Alexia, Isomac Zaffiro (and other similar E-61 SBDU machines) have a brew sensor inside a vertical thermowell. So the temperature is being sensed at a point closer to midheight of the boiler. Gaggia machines with aluminum boilers have the brew temperature sensor down near the base of the boiler.

In general, the brewhead is too slow to respond to changes in heater output to be an effective location for a single sensor. There would be too much lag, making it pretty difficult to control the system.

Jim

Thanks Jim. Appreciate the response. I do understand that the sensor needs to be somewhere in the boiler in order to respond quicky to temp changes. In my Silvano I believe it is at the top of the boiler. But I thought there are some machines that have two sensors, one in the boiler and one at the grouphead as well.

Steve -

It's quite possible that there are 2-sensor machines out there. I'm just not aware of any -- at least not any that use the 2nd sensor in the control loop.

The closest I've seen was a SBDU machine with an analog thermometer connected to the grouphead (which I thought was a great idea). The thermometer's dial was mounted in the front of the machine, similar to the way many machines have a pressure gauge. I'm struggling to recall the brand (but I do recall that it is no longer offered in the US).

Jim