The Overhaul
Since the last update, a lot of hardware work has been happening on the bench. I picked up a **Gaggia New Baby 06** to serve as the new testbed for the Oximite system.
The first order of business was a complete teardown and overhaul of the machine to ensure a clean baseline. Overall, the restoration was a huge success, with the only lingering mechanical issue being a stubborn Over Pressure Valve (OPV) that currently isn't working as it should. I'll need to circle back to that, but the machine is otherwise structurally sound.

Making Room for Brains
To actually test the custom electronics, I needed space inside the chassis. I ended up 3D printing a set of custom pylons to hold the main mounting plate. This simple mod effectively creates a lower "basement" compartment giving me plenty of clearance to securely install the prototype control boards and run wiring without interfering with the high-voltage or wet components.

Data Logging the Factory Thermostats

Before stripping out the original control loop, I wanted to understand exactly how the stock machine behaves. I installed an NTC thermistor and spent some time logging the thermal curves driven by the factory brewing and steam thermostats (which are an absolute mechanical beauty to look at).
This data logging led to a fascinating realization about my software design, and raised some great engineering questions for the next phase.

The "Burst Mode" Dilemma: To Boost or Not to Boost?
In the current iteration of my software, I implemented a "burst mode"—a feature that artificially spikes the heating power the moment a shot begins to compensate for the influx of cold water into the boiler.
However, looking at the thermal graphs of the stock machine, I'm starting to think this software boost might be unnecessary. The data shows the factory setup sitting at a rather hot mean temperature of ~101°C right before a shot. As the shot starts, the water rapidly loses heat to the group head and portafilter (a drop of about 7 degrees), bringing it perfectly down to the ~94°C "sweet spot".
As the shot progresses, the thermal losses decrease at roughly the same rate as the boiler temperature drops. It looks like the Gaggia engineers relied entirely on this natural thermal balancing act to keep the output temperature surprisingly stable!

Next Steps & Experiments
To validate this theory, I need to run a controlled experiment:
1. Simulate the exact water flow of a real espresso shot.
2. Accurately log the *output* water temperature (hitting the puck) under two conditions: **with** my software burst mode enabled, and **without** it.
3. If the boost is needed, determine exactly what percentage of power yields the flattest thermal line.

Plot of brew mode temperature

Steam mode