Hi All: Does anyone have a machine (modified or factory)that is PID'ed but uses a pressure transducer instead of a thermocouple or RTD? I was wondering how that might work out in terms of repeatability and accuracy over time. I think most or all controllers can accept a 5-20mil or 0-5volt signal out of a pressure sensor, certainly such controllers are available. Might be more expensive to set up as decent pressure sensor is more $ then a T/C or RTD, but might work better in the long run. Any ideas?
KDM

The only machine I've heard of that uses a PID coupled directly to boiler pressure is the Nuova Simonelli Aurelia Competizione (the WBC spec machine).

It's doable, easier and more fun than installing thermocouple. All you need is pressure transducer, PID accepting its signal and a SSR. You can find digital pressurestat as well. Moreover you can play with an Arduino



I have bought mine Norgren digital pressurestat on Ebay for 65$ (new), however retail price is approximately 250$. It works flawlessly, no clicking, pressure adjustment every 0,05 bar or 1 PSI, great stability and repeatability, very fast response to pressure changes. Highly suggested mod.

Maciolus: I'm interested in pressure sensor/PID or digital pressurestat set up but as I look around there are just too many parts out there, especially transducers. Could you post the brands/model #'s of what you are using?
Thanks, Duke Masters

I think Auber Instruments has a 0-5 bar pressure transducer around $70.

Fun part (and cheaper) is that Arduino analog input has 10-bit resolution and that is very good to convert 0 to 5000 mbar sensors (0-5000mV). If you want to read thermocouples with good resolution you have to add some higher resolution AD converter as we do with the TC4 board from Jim.

Márcio.

For Magnus - The Rancilio Class 8 utilizes a pressure transducer - I have a possessed Faema F/83 . I would ASSUME their Class 10 does also.

The less expensive PID controllers (~ $35) will not accept inputs other than thermocouples and RTD's.

@ duke-one: It's Norgren 33d pressure switch.

For 30$ you can buy a 30PSI pressure transducer with 0,5-4,5v output on ebay. 20$ for an Arduino, 5$ for a power supply, 10$ for 25A SSR and 5$ for project box and wires. There is a free PID library (software) available for Arduino online. Total cost of the project will be around 70$.

For 30$ you can buy a 30PSI pressure tranducer with 0,5-4,5v output on ebay. 20$ for an Arduino, 5$ for a power supply, 10$ for 25A SSR and 5$ for project box and wires. There is a free PID library (software) avalible for Arduino online. Total cost of the project will be around 70$.

Add $5 for a 2 year supply of 81mg aspirin from Costco .

As far as "working better" in the long run, that would be an ad infinitum discussion. For someone with your skillset, it would be a couple of hours work to apply either - however, applying a temperature controlled PID is physically easier. You can maintain the existing pstat as an additional safety device simply by bumping up its opening setpoint and wiring accordingly. The components required to go either way are ~ 80% identical. But, short of getting a good deal on a pressure transducer, the cost to apply this methodology is substantially more.

Instead of a pressure sensor you might want to look at a temperature probe (Thermocouple/RTD/NTC etc.) instead. I did quite a few experiments to compare the 2 systems in 1994 when working on the GS3 project. What I found was the temperature probe actually performed a bit better (at least with my system) than the pressure sensor. Additionally it was easier and lower cost, to find off the shelf components for temperature measurement then pressure measurement.

As long as the probe is immersed in the vapor (can't be a surface mount probe on the outside) of the boiler it works excellent.

Forgot to mention that most all newer La Marzocco Machines use a temperature probe in the steam boiler to control pressure.


BillC

Billc wrote:As long as the probe is immersed in the vapor (can't be a surface mount probe on the outside) of the boiler it works excellent.
Forgot to mention that most all newer La Marzocco Machines use a temperature probe in the steam boiler to control pressure.

Due to seasonal variations of atmospheric temperature often have to adjust the temperature of the brew by correcting the pressure (coffee machine works almost in the street, range from-5C to 30C).
It has long been willing to release the mechanical pressure switch, replacing it with a PID (auberins).
Boiler 12 liters. For such large boiler, the control is very easy. I can use the auto-tune to set the PID parameter.
Do I understand correctly that the temperature sensor is installed in the area of steam, that there was no contact with the water?
Which features of PID settings and installation should pay special attention to?
Thank you.