5V and 12V output current

[lrodorigo]

Hi all, I am trying to design a fully isolated board compatible with this project, based on ESP32 (I will be happy to share details once it is completed).

Has anyone actually measured the output current on the CN-CNT connector?
Are 250mA actually available also on the 12V pin? In this case a 12-5 DC DC isolated power module is a best fit since 3W (minus the conversion efficiency) are enough for properly powering the module.

Regards

[IgorYbema]

Never has been measured and probably different for each type of heatpump also.
If you want to share your design please do so, so I can improve the current board. If you want to be a co-author of the board I would be happy to have some help

[lrodorigo]

Wow, I will be so glad! Please check the brand-new project repository: https://github.com/lrodorigo/heishamon-lr-aquarea-board Hope this will be helpful for this great project

[ElVit]

Hi sorry for interfering your discussion.
I tried something similar but only with a prototype PCB.
I used an adum1201 to isolate the signals.
PINs are probably different to the Heishamon implementation because I use my own implementation (converted Heishamon into an ESPHome component).
Here my schematic:

As far as I can see you are using IS3862LW or ISO7762FDW.
Unfortunately I couldn’t find them on AliExpress.
Sorry I have only basic skills in designing PCBs.
Do you know a similar isolator which I can find on AliExpress with 4 lines?

[lrodorigo]

Hi, and many thanks for your schematic. I used it also for checking mine.
If you open on KiCAD my project, you will find the LCSC reference designator.
You can buy components on lcsc.com, at great prices.
Once I checked if it is properly working, I will share the PDF BOM. Now I am not sure how I will power the module.

[lrodorigo]

Hi, I just assembled the first board, and of course first problem arise. The 12V cable is not present on my heatpump. The cable from the HP mainboard to the CZ-TAW has only 4 wires, and the 12V wire is missing. I will try to use the 5V (it is sufficient to place a 0505 DC converter instead of 1205 and move a resistor.

[IgorYbema]

It is just the wire missing (so it is connected to the 5-pin port)?
I would be happy to send you a 5-wire cable for that if you want

[lrodorigo]

I Will check this afternoon if the 12V is actually present on the motherboard, but it is a 2021 model J, so I think it is just the cable missing. Many many thanks, of course let me know the total amount *Luigi R.* Il mer 25 giu 2025, 10:35 IgorYbema ***@***.***> ha scritto:

…

It is just the wire missing (so it is connected to the 5-pin port)? I would be happy to send you a 5-wire cable for that if you want — Reply to this email directly, view it on GitHub <#687 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACBHPUEXEDODBFWDJDDOUQD3FJNOXAVCNFSM6AAAAAB6UO4Q5KVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGNJXGEYDGMA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[IgorYbema]

for free ofcourse :)

[lrodorigo]

The shipping cost is on my charge! I send you an email with details.

[lrodorigo]

I can confirm that, after some code customisation (i.e. disable the ethernet port, disabling additional IOs...) the module is now working like a charm!
It uses the 5 Vdc from the HP, so I soldered a 0505 converter. The drawn current is 120mA maximum so it is quite stable.