GS/3 Mod EP "Chimera" - a fully configurable profiling mod for La Marzocco GS/3 AV - Page 8

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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AssafL (original poster)

#71: Post by AssafL (original poster) »

As for 1: I was thinking one of these "bending" potentiometers. You connect it to a level (lust a lever and a spring) and as the sensor flexes the pour increases.

As for 2: I was thinking about this - sort of an open sourced espresso machine controller. It shouldn't be too hard, but note the 3d5 has lots of safety timers thermal controls and is pretty robust. When I took a look and tried to put a shopping list of controls and features (e.g. heater safety; e.g. after X seconds if T boiler doesn't rise - stop the heater; autofill timers; etc.) it was quite a long list.

3: Yup - wanted to do this as well.

That said, I am spending time on 2 startups, and roasting and have a 7yo with lots of interests (which became my interests). So Chimera won't progress with me (unfortunately).

Back in 2017, I was in-between stuff and had a month or two to pour into this. Also, Jake's solution is really cool and cheap.
Scraping away (slowly) at the tyranny of biases and dogma.


#72: Post by Tobias007 »

Here some early preview pics:

The build in scale is most useful "tool" meanwhile :)

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AssafL (original poster)

#73: Post by AssafL (original poster) »


Is the temp from the 3d5 or something else?
Scraping away (slowly) at the tyranny of biases and dogma.


#74: Post by Tobias007 »

Temp is from the PT sensor of LM. I replaced the 3D5 with my own one (2x ESP32 - one for temperature PID, another one for all the rest). It's so much better control without 3d5 :).

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Team HB

#75: Post by Jake_G »


As I have not one, but two esp32s in my nerd bag right now...

You got this on github?
LMWDP #704

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AssafL (original poster)

#76: Post by AssafL (original poster) »

How I long for unemployment right now.

It would be cool if Jake's machine reboots with an ESP32 as well. Now that would be a head scratcher!
Scraping away (slowly) at the tyranny of biases and dogma.

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#77: Post by Peppersass »

So you wrote you're own PID and control code??? Wow, now that's way beyond what us other GS/3-mod nerds have done.

Do you have some sort of interface board with relays to activate the motor, solenoids, etc?

Is the programming language C? Have you put it on GitHub?


#78: Post by Tobias007 »

I replaced the 3D5 board entirely. So own PID (which triggers the SSRs) was needed. As PID algorithm I used the existing libraries (same as Assaf).

The interface board I had to build up from scratch. Solenoids will be triggered by new SSRs. Temp sensor, the existing one is good enough. I used a MAX31865 for signal conversion...


#79: Post by Tobias007 »

PID tuning still necessary (even if pulses from flow sensor are perfectly linear) - overshoot at flow profiling. And Temp control not there, yet.
As well grind might be too fine - so to get constant flow the pressure went up to 12 bar ...

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#80: Post by Peppersass »

What device are you using for the UI?

My UI runs on an Android tablet or phone connected via BT to the scale and an Arduino that monitors and "controls" the GS/3. The Arduino features are similar to Assaf's but without the ability to record and playback profiles. So my Arduino doesn't replace the 3D5. It monitors the GS/3 motor, tea water and power on/off signals, as well as flow rate via the GS/3 flow meter, pump pressure with a transducer at the pump output, and pump speed (gear pump with an RPM output.) It also can trigger relays to start/stop the brew cycle (wired to the front panel brew button) and needle valve solenoid bypass valve.

Some screen shots:

Android interface when GS/3 is idling. I've since added motor speed and shot volume to the line above the top row of brew buttons. The Flow button engages/disengages the needle valve solenoid bypass valve. The Pre-Brew button does a Slayer-like shot, starting with the parameters below the button. When preinfusion ends, the parameters under the Brew button take over. This allows me to gradually reduce pressure to keep the flow rate constant after max pressure has been reached.

During preinfusion for a "Slayer-like" flow control shot.

Graphs for the shot just completed. The readings below the chart are for debugging, which isn't enabled in this screen shot.