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Theory of Operation question about the switching of the contactor

Hi there,

I'm new to this so I just want to understand something that for me is not clear after analyzing the schematics and diagrams (and also some topics in this forum).

How does the MCU control the switching of the contactor? Is it using 230V or 12V? 
If is it 230V, what is the circuit to allow the MCU (+5V) to control the 230V switching?
I'm asking this because for the 3-Phase version of OpenEVSE a 230V coil contactor is assumed to be used (and also for some version of the 1-Phase version as well I think). 

Thank you.



OpenEVSE controllers have 3 relay outputs, two 12v DC outputs and an AC output that switches the AC input voltage.

The circuit switching the AC input voltage is a Panasonic AQH2223 SSR.

Here is the wiring diagram for a 3 phase setup.


Thank you for the explanation, Chris.

For the 3-Phase setup, do you recommend any 4 pole contactor/relay? And why do use say it requires and RCD breaker?

Thank you.

You can use a standard breaker with the OpenEVSE GFI or an RCD breaker which includes GFI.

Availability of contactors varies greatly depending on your country/region. Any 4 pole relay that meets your current requirements will do, ensure the coil voltage matches your input line voltage.


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