Add support for Expansion Valve

[bagbag]

I've added support for the expansion valve after me and some other folks (thanks to them!) verified that it actually is it using external measurement probes on the EEV wires:

[geduxas]

Hi, thanks, it was observed, and i could also step and actually confirm it from EEV, also i think next byte could be for bypass valve in t-cap models.. it's required for more investigation

Here is more info: #298

[bagbag]

For reference:

This was verified using a board that was developed specifically for measuring (and optionally controlling) the expansion valve of the panasonic heatpumps by intercepting the signals of the main board.

Each step the heat pump reports are 4 half steps at the stepper motor for the expansion valve. Or in other words: a half rotation of the valve.

[geduxas]

nice work! maybe you also could confirm for bypas valve ?

where could i read about your project? is it open?

[bagbag]

Thanks! No one of us have a T-CAP. So there is nothing we could measure. The packet itself only reports a 1 for us (but I guess you know that already).

We are a a group of a handful of people that found each other at https://www.photovoltaikforum.com/. Some can design PCBs and are good at hardware, some can develop software, some try out a lot of stuff and look for explanations why the heat pump does what it does. And one guy is crazy.

It's nothing that's baked to production readiness (yet). The prototype that can be seen on the picture is a Raspberry Pi with a simple C "script" connected to that custom PCB that sends the measurements via mqtt. Currently only read-only.

There is a attempt I did to measure and control the EEV with an ESP32 that could be plugged into that PCB (thats why it has those pins) at https://github.com/bagbag/heishamod. But I havn't had time to finish it yet. It's made with esp-rs (Rust).

Here is the PCB design:
250325_ SCH_Pana-Eex_2025-03-25.pdf

It's meant to be open someday, but as it's not ready yet, there isn't any polished documentation or similar.

We also do and plan to do other things like controlling of the fan to get rid of that stupid reduction at 40+ Hz.
Some use Shellys and put resistors into the circuit of some NTCs to have a "dip killer" (the PID controller of the EEV reacts to that and we can reduce icing and increase COP that way and also reduce likeliness of a deice operation when there is no ice).

[dnoermann]

nice work! maybe you also could confirm for bypas valve ?

where could i read about your project? is it open?

Its open, i just did not had the Time to put the Shematic and Layout on github, will do it soo you can find it than in my repo

[IgorYbema]

I'll add this to my repo to