Hellos,

I think I am probably the last person on the planet to consider PID temperature control...

My current machine is a commercial LaPavoni single group from about 20 years ago. I have recently been convinced that adding a delay relay to add preinfusion simple and effective mod. Now that the barn door is open I have been thinking about PID to simplify the temperature surf dance...

Looking at the part numbers A PXR3-RCY1-5V is similar the to 4V that everyone mentions using for the controller except it has an alarm function that could be used as a failsafe in case the solid state relay fails in the "on" position. I would be interested in hearing if this is a good, bad or crazy idea..

I have been thinking about a hypothetical 2 group machine. and being able to control the temperature of both boilers. In this case a controller of the form PXR3-RCCY-4V could be used to control the temperature of both boilers. I realize that you would give up displaying both temperatures simultaneously, but I am also curious if anyone has played around with anything other than the basic PXR3?

And as an aside has anyone played with the RS485 interface option. Although it might be interesting to be able to log data and program the controller with something other that the little buttons on the front I have been thinking that a pid controller capable of taking input from computer might be used to hypothetically drive a temperature profile of a roaster.

Right now the biggest problem with my coffee is the loose nut in front of the machine is not consistent enough!

Thanks.

pavoni wrote:Looking at the part numbers A PXR3-RCY1-5V is similar the to 4V that everyone mentions using for the controller except it has an alarm function that could be used as a failsafe in case the solid state relay fails in the "on" position. I would be interested in hearing if this is a good, bad or crazy idea..

An effective fail safe function should be independent of the PID controller. The typical way to do this is with an inexpensive snap action thermostat mounted in contact with the boiler surface.

pavoni wrote:I have been thinking about a hypothetical 2 group machine. and being able to control the temperature of both boilers. In this case a controler of the form PXR3-RCCY-4V could be used to control the temperature of both boilers.

No. A dual output controller is like your home heating thermostat. If your house is too cold, the first output stage turns on the heat. If the house is too warm, the second output turns on the A/C. That's completely different than your example of controlling the heat of two boilers.

Very few 2 group machines have 2 boilers anyway.

Thank you for the reply, I mistyped.... it should have been dual boiler single group
But it sounds like a single box solution does not work! If I wanted to control the temperature in two boilers two controllers would be needed.

pavoni wrote:If I wanted to control the temperature in two boilers two controllers would be needed.

"Dual loop" controllers are available. They accept two separate inputs, process them independently, and control two separate outputs. In theory, the savings realized by having only one enclosure, one display, etc, should make them a good buy.

But it appears that companies sell a hundred single loop controllers for every dual loop controller. So the dual loop controllers tend to be quite expensive.