I am puzzled by the hestia-pi-touch PCB setup.
The G3MB-202P 5V needs 5V to turn it on based on the datasheet. But, Raspberry Pi Zero GPIO pins connected to the relay can only give HIGH with voltage between 1.8V and 3.3V.
So, how can it turn on/off the 5VDC relay to control the HVAC?
Your explanation is greatly appreciated!
There are transistors involved to “switch” the 5V trigger supply to the relay with the 3.3V signal off each GPIO pin involved.
Thank you for the fast reply! Sorry, I still don’t know how this work?
Because, when I measured the input voltage of the relays’ pins on my hestia-pi-touch they are only around 3.1V. Did I miss putting transistors on my PCB?
Oh apologies for the confusion… I was talking about the older boards. The relay you are referring to also works with the voltage levels provided by the GPIO pins.
Thank you for clarifying this! If I understand it correctly, even G3MB-202P Solid State Relay stated on the datasheet it needs 5V, actually we can turn it on with much lower voltage from the GPIO pins. Right?
That is correct 
Thank you for your explanation. Now, I feel more confident to try it on my HVAC.
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