Gaggia Classic, Schematic diagrams, PID-ing

Equipment, technique, or just drinking the stuff

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Postby lukas » Fri Aug 11, 2006 8:29 pm

You finally made me jealous. I'll order a PID from this palmguy as soon as I find somebody willing to "lend" me his paypal account (no, I won't even create one for this very opportunity), an SSR which switches at 3V is on it's way, too. Won't be long for me to join the PID-Club! I just can't get these numbers out of my head ... 88°C ... 116°C ... 88°C ... 117°C ...
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Postby ben_edwards » Fri Aug 11, 2006 10:15 pm

hehe... now along with those numbers repeat after me "I must remember to earth my arm before inserting into a live espresso machine". I just don't want any more life threatening accidents due to this thread!
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Postby Captain_Crema » Sat Aug 12, 2006 8:33 am

Ha! You wanna see the scar?
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Postby Captain_Crema » Sat Aug 12, 2006 8:36 am

Captain_Crema wrote:The temperature cycle is between 94 at its coldest and 113 at the hottest (and I can see it is overshooting quite a bit, as the heater turns off way before the temperature stops rising).



I think that is what you were after, Ben, and I am beginning to suspect you're right about the setpoint.
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Postby mocha » Sat Aug 12, 2006 7:07 pm

Gaggia owners should notice that it's a genial machine with bad temper. Trying to approach the Gaggia like a Sylvia may be painful. The best way to avoid the temp lag is to go farthest away from the heating elements. It's down at the front side of the boiler between the two boiler fixation screws. A sheet metal bridge inbetween would be the ideal clamping device for the PID-sensor. The measured temp at that location corresponds exactly to the temp measured at the cup-test (brew water at the styropor foam cup). I guess the water leaving the shower is 2-3 C above.
You can try following: sensor as described, set PID to ON-OFF mode. To get a constant 91 C measured, you will notice that a PID setting of 86 C is required (that eliminates the lag as good as possible). Taste the coffee!
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Postby knewmans » Sun Aug 13, 2006 3:42 pm

Mocha, how did you do your "heater always on" steam mod? Photo would be great.
Thanks
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Postby mocha » Sun Aug 13, 2006 8:38 pm

knewmans wrote:Mocha, how did you do your "heater always on" steam mod? Photo would be great.
Thanks
Ken


Hi Knewmans, there is a photo:

http://i96.photobucket.com/albums/l166/ ... cn0980.jpg

it's possible to percieve the sheet aluminum cam fitted on the shaft of the steam valve (a shiny piece) and the microswitch (blue color) with shortcut connection to the steam thermostat (not seen on the picture). Wenn the valve knob is operated, the microswitch lever (difficult to see here) will be released to short cut the thermostat for continious heating. Closing the valve pushes the lever to terminate the shortcut. The already existing thermofuse remains the ultimate security in case of mechanical failure of this system, and if the machine is not shut down after the steaming operation (such a failure didn't happen after more than a year). Some kind of mechanical precision is required to home-build this device. The steaming
efficiency gets an amazing boost..
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Postby mocha » Sun Aug 13, 2006 8:43 pm

knewmans wrote:Mocha, how did you do your "heater always on" steam mod? Photo would be great.
Thanks
Ken


Sorry, that was the wrong photo, correction:

http://i96.photobucket.com/albums/l166/ ... cn1086.jpg
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Postby knewmans » Sun Aug 13, 2006 10:34 pm

Thanks, that's clear. The Classic is slightly different but I can see how you've done it.
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Postby lukas » Wed Aug 16, 2006 9:32 pm

Yay! PID and SSR on order. Can't wait for it! Must. Have. Now. Want want want!
Lukas

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Postby ben_edwards » Wed Aug 16, 2006 9:54 pm

Congratulations Lukas! :D You wont be dissapointed.. Hey even if you can't taste the difference it still looks so damn good! ;) The PID took about a week to arrive so in the meantime you will have to buy crimps connectors, some heat resistant wire and a project box :)
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Postby chemistone » Thu Aug 17, 2006 4:53 am

Captain_Crema wrote:
Captain_Crema wrote:The temperature cycle is between 94 at its coldest and 113 at the hottest (and I can see it is overshooting quite a bit, as the heater turns off way before the temperature stops rising).



I think that is what you were after, Ben, and I am beginning to suspect you're right about the setpoint.


Did you fine-tune the PID, if you have the "wrong” settings the machine will overshoot whatever you do. The temperature reading must be at the right position as well, as a PID works the same as with coffee, rubbish in = rubbish out.
When I come back from my small break I will have a look for a PID fine-tune procedure.
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Postby ben_edwards » Thu Aug 17, 2006 10:46 am

Umm... I'm getting a little bit confused with this thread now but tI think that quote was for the original thermostat operation. The PIDs were autotuned and sit tight at setpoint with no major issues. I had a few probs with the PID displaying Fahrenheit as I think it was basically just converting Celcius into Fahrenheit with a nasty integer or roundoff error in the maths. The fuzzy logic was being highly illogical too :) Set on normal PID mode with display in C it is performing admirably. The only con I can think of is that I now can see the temperature so always want to wait until it gets back to temperature before pulling the second shot! This seems like a loooong time but its really a few mins. I think this is where we can make use of the fine tuning - to get a better recovery time. My settings give almost no overshoot - I think I can cope with a little overshoot say 1C to get a faster recovery. So I will look forward to hearing of this fine tune procedure :)

While I remember, Lukas, if you have the manual for the PID (did you get the ebay one me and Jon got?) there are a couple of mistakes:

The example setup (an espresso machine boiler coincidently) states heating/cooling (r/d) = 1 (cooling) it SHOULD be 0 (heating)
The manual also states default temperatures of 80C... on my PID this setting showed as 0800, so I assumed the last digit was a decimal place. Wrong. the default on mine was 800C, when you set the temperatures each digit is 1C so 80C would be 0080. No wonder my espresso machine was glowing red when I first set it up the PID was trynig to hit 800C ;)
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Postby lukas » Thu Aug 17, 2006 9:45 pm

Uaargh, whoops! Thanks for the warnings, Ben. I'm sure with my luck at technical things I would have burned our kitchen! ;) (ok, I built a small CPU a few weeks ago, but that was programmed on an FPGA with a good testsuite running over it before so nothing got boom there :lol: )


edit: oh, forgot: yes, it's the same one from this guy in Hong Kong, the XMT-bla7100 or some such for nearly no money at all ;)
Lukas

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Postby Captain_Crema » Fri Aug 18, 2006 2:40 pm

Yes, it is a good price isn't it? Ben has said it all, really. I forgot about the setting and 800degree C setting. But it works fine on the standard PID especially if you help it get to temperature with the steam switch. I have not found the right setpoint yet, because I'm short of time. I'm hoping Ben's going to come up with the goods on that. The scar on the back of my hand is healing nicely and I have another SSD to fit, plus a project box to acquire.

In the meantime, my shots are still awful.

<sigh> So little time...
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