Posted Thu May 2, 2013, 11:23am Subject: Re: Next Mod: PID my Gaggia Classic
I've made these before but I hadn't worked with this particular material with an adhesive backing before. It cut really nicely but it was a b*tch to install. The adhesive is SUPER sticky... but forgivable enough to allow me to push it around into the correct places.
Now, the Gaggia's stainless steel face is protected by the new face plate.
Posted Thu May 2, 2013, 11:37am Subject: Re: Next Mod: PID my Gaggia Classic
I've already been looking at the steam system. The steam port on the sensor mount lines up perfectly... or near perfectly with the knob hole, so the plan is this:
- Since the steam port was cut to1/8 NPT, I'm going to install a ~2" 1/8 NPT brass pipe (should be fairly easy to find at Home Depot or any local hardware store) into the steam port.
- Attached to the end of the brass pipe, I'll install a 90 degree ball valve. The knob facing the hole, obviously, and the exit facing down. I'll have to make an adapter to go from 1/8 NPT to M10 (or M18 to fit the Silvia V3 wand directly, which should take up about 3/4" at the top of the steam wand). A ball valve will allow full on/full off with a 90 degree turn, instead of 3-4 full turns. Of course, this limits the precision of the stream output, but just from my experience, it's usually partially on to start, then full on, which isn't too difficult. That's how it is on commercial machines also (1/4 turn).
- I'll fabricate a custom knob, probably out of stainless steel for that nice stainless, commercial look.
- And that SHOULD be all she wrote, unless something unexpected happens... which we all know could and most likely would.
The only problem I'm having with this setup right now is the 90 degree 1/8 NPT is hard to find. McMaster has one but it's in the $35 range.
One of the 5 buttons will control the 3-way and raise the PID temperature to say, 235-250F to develop steam.
Well, at least SOME good comes from a slow economy. I get a little more time to work on my PIDruino project... although I have other internal products to work on.
Posted Thu May 2, 2013, 2:21pm Subject: Re: Next Mod: PID my Gaggia Classic
More pictures of progress.
In the BUFF!
In case anyone wants to take off the Gaggia Classic emblem, be careful. First, it's NOT plastic like we would tend to think. It's probably tin, very soft and I nearly broke it, pulling it off. There are, as you can see, three holes for three pins (also very soft). Just remove the boiler from the four bolts at the bottom and unbend the pins. The emblem should pull right out. You probably don't need to remove the boiler, but it took all of about 60 seconds by doing so. Otherwise, I'd say 5-10 minutes minimum.
Posted Thu May 2, 2013, 2:25pm Subject: Re: Next Mod: PID my Gaggia Classic
Here it is, giving me the current time and date (actually it's slow by ~10 minutes. I'll have to fix that later), and the two internal thermocouples. The heaters aren't on, so it's "room temperature" water.
The five "L's" are reading "LOW" status on each of the switches. They individually go "H" for "HIGH" when pressed. The LED's light up blue when pressed as well (not shown in pictures).
Posted Thu May 2, 2013, 2:28pm Subject: Re: Next Mod: PID my Gaggia Classic
Well, it's not done yet. I still have to do the following: - Hook up the SSR for the pump - Hook up another SSR for the 3-way (which I forgot to account for, so I think the third TC amplifier has to be sacraficed - Install a 5 volt power supply inside the machine for the electronics - Finish the program
The program will be a work-in-progress, so it will probably never be "done".
I have to get it at least working tonight so I can have espresso tomorrow. :D
At some point, I still have to find some suitable smoke tinted film for the face.
Posted Fri May 3, 2013, 9:44am Subject: Re: Next Mod: PID my Gaggia Classic
Alright. I was too excited to see this puppy in action, I hadn't finished putting in the SD and implementing the data logger, but hooked up everything else and too her for a test run.
Since the datalogger isn't connected, I have no qualitative results at this time, but I can say that starting a shot at 200F, I'm ending it (around 25 seconds) at around 175-180F consistently. Now, that still seems a bit low, and I'll start tuning that in the software (and can only optimize it as far as the hardware will allow), but it was dropping to around 165F before the current PID algorithm.
Since my controls are completely under digital control now, I can and will implement a 'preheat/prep' sequence with the shot button. This will not start the shot immediately. It will get the heaters warmed up and ready for the inrush of cold/cool water, so the 'burners' will be heating the cool water as quickly as possible, but shutting down before the shot is done (maybe on a 10-15 second timer, starting when the shot button is pressed) so it doesn't overshoot the target temperature. Hopefully, this should narrow this temperature window for a more precise espresso.
With a multi-channel thermocouple system, I have tried basing the PID function on the external TC, and although the temps between external and internal water normally remain close (within 10F of each other), there is a terrible lag (somewhere around 5 seconds). However, with a good algorithm (my hand coded/non-PID), I am able to predict and keep the temp stable within 0.1F (non-shot). With an implemented PID algorithm and a bunch of tuning (not done yet), I'm within about 1F (displaying the external temp, not the water temp).
I'm finding it much more difficult to keep the actual water temp within 1F with a PID algorithm. So far, I'm within ±15F. I'll install the SD module today so I have actual numbers to work with.
So far, so good! Espresso is much better today, probably since the temp is not dropping to 165F. Time to close that gap.
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