I recommend u do the job . I have my classic improved with adding pid controller , plc time relay， preheat copper pipe ,pressure gauge and etc . Upon that I got adjustable brew pressure which was set at 8.5 bar, much more precise temperature control and adjustable pre-fusion time. I needn't calculate the brew time any more when I push the brew button. It is easier than you ever thought even compared with Silvia. You can add temperature picker at the lower part of the boiler where is the coffee brew temperature sensor placed without drilling. I think it is better than silvia which have the sensor placed at the top. And you can adjust the brew pressure only turn the screw after you remove the cover from the safety valve. You need not add any washer there and worry about leakage. The most difficulty is adding the time relay I think. I add two relays and switches to help the plc time control. Finally I got everything done and I got much pleasure from diy . I have tried to add a device with a potentiometer to control the heat elements' power which can heat the boiler immediately and maintain the water temperature when I brew the coffee. I feel the pid is a bit delay to control the heating power when I brew coffee but work properly at the static time. But I failed due to the none linear heating curve and no any more space in the machine. Maybe simple is the best ,I didn't plan to complicate it any more .

tmaynard wrote:I, for one, would be interested in hearing this story. I have an unmodified Gaggia Coffee, and temperature surfing (after grinder tuning) is my next area of interest.

Do tell!
t++

I didn't want to hijack this thread with this so I started a new thread...

Preheating the incoming water on a Gaggia Classic

An update.

Sitting here on a laptop, waiting for the now-PIDed Espresso to finish calibrating itself. It should be noted that while the AuberIns manual is decently written, their thermocouple quality seems to leave a lot to be desired; I had to remove the washer termination and recrimp it to get a decent connection.

In light of the one other Gaggia PID effort that I could find, I'm calibrating to 210°F... and I'll work from there.


Had to go to radio shack as I wanted to power the PID off of DC rather than AC (mainly because I'm comfortable with DC and have never worked with 110v, 15A mains power)... and found that my local one no longer carries enclosures (so I'm using a jury-rigged object... it works, it just looks a bit odd).

Sonicjason and Swemarv, very impressive work! I like it a lot.
Beanmuncher, I've had some experience with the Auber PID. I have one installed on my La Pavoni pump machine with similar internals to the Gaggia. Instead of using a thermocouple though, I'm using an RTD which provides 0.1 C resolution for more accurate reading. I think it helps a lot. I've also mounted the RTD in a brass nut I've machined myself that's screwed into the top of the boiler, measuring something very close to actual water temp.
The autotune algorithm on this controller is virtually useless. I've never gotten it to get anything close to usable parameters. Basically I just tuned mine with a LOT of trial and error. To start off, I recommend P I and D values of about 2.1, 60, and 17. Autotuning will give you much higher values which will either take forever to stabilize or not stabilize at all. One thing that is important to note is that the P value is entered into the controller as a percentage of the input range, which is very different from most PID controllers. The way I understand it then is that if your input range is -200 to 3000 degrees, range is 3200 degrees, and so 2.1% of that is 67.2 - and that is the actual constant for P.
Anyone out there who understands this stuff better than I do feel free to correct me please!

Take a look at erics' re-written documentation for the Auber PID over at http://users.rcn.com/erics/PID/ and click on PID_Manual_2.doc. It's much clearer I think and explains some functions a little better than the original documentation. Hope to hear from you with some progress.

Well, after a little more tinkering with it I found that my setpoint was drastically too high (210F) - the whole tons-of-steam-coming-out-of-the-head bit... reinstalled the stock Tstat and took readings using the TC held in place by the Tstat itself... generally 180-190F on the surface of the boiler; seemed to stabilize around ~182 or so. So, I'll tweak it later.

I'm not very happy with the Auber TC... had to reattach the TC washer as it was so poorly attached.

As I've just moved back into the dorm, and life is a bit crazed right now, I've put this project on hold. I think I know what I'll need to do to make it work, but I don't have the time to do it right now.