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Discussion Starter · #1 ·
Hello fellow campers,

I am attempting to replace my manual changeover config with a DIY automatic changeover config. The brains an Arduino. This monitors the incoming shore power and should power be detected it then auto switches to shore, if shore power fails or is disconnected (once had this with some annoying kids who thought it amusing to disconnect us) the power reverts back to the inverter. The Arduino monitors the 5v input fed by a mains transformer via pin D2, should this drop to low i.e. power failure, with a bit of code the Arduino sends a signal to the relay to switch from NC (shore) to NO (inverter). I've put together the attached, rudimental schematic. There are a few extra bits I want to add, for example, another relay to switch inverter on/off for more efficiency and in cab indictors to show where power is being fed from. Can anyone see any issues with the attached schematic? Would I need some for of capacitor between the COM connection of the relay and camper power system to iron out power disruption i.e. when the relay changes from shore to inverter or vice versa?

I await in anticipation for your comments.
Rectangle Schematic Parallel Plan Slope
 

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Discussion Starter · #3 ·
Hi,

No don't own a boat and no not an ex sailor 😂. I was actually referring to EHU (electric hook up), not sure why I've said 'shore' just sounded good at the time! Boat 🚢⛵
 

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Discussion Starter · #7 ·
The idea is sound. But you may need a capacitor after the diode from the 5v tx to hold that output for a short while.
A dodgy mains input from "shore" would cause the relay to chatter on and off which wouldn't be great. Ideally if "shore" power drops you want to switch to inverter quickly. But on detection of "shore" power there is a delay to ensure its stable before switching over.
You can buy ready made timer units for that. And use that output to also turn on and off the inverter.
Hi Pat,

Thank you for your advice. Just a thought I could hold the relay for say 100ms longer/shorter in the code of the Arduino this could also prevent 'chatter' from an unstable hook up power, this could work either way i.e. shore to inverter, inverter to shore?

Thank you for all the other comments re off the shelf units. I appreciate that this is an option, however, there are other more custom things that I can do with my DIY set up, for example logging power failures, time on shore, time on inverter, power consumption (with a few additions) and push notifications to name just a few. I'm not sure I would have this much customisation with ready to go options?

Regards,

David
 

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Discussion Starter · #10 ·
Hi Pat,

The delay can be set to whatever value we require I believe within the code so shouldn't be a problem.

Arduino over Pi, I have an Arduino and a number of relays. Can't get hold of Ras Pi's at the moment, certainly not on Pihut! Do you think a Pi would be better?
 
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