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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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2017 Hymer Exsis-i 504
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Haven't a clue about the electrics allen but just wanted to say welcome to the forum.

Are you on a boat, or just an ex-sailor? The talk about shore power confuses me (doesn't take much!)
 

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Hi alan im sure there is a ready made box for just that

I had a motorhome that i was working on that could automatically switch over to battery if it lost mains power

Try the bigger companys that supply solar panels and inverters for motorhomes

Barry
 

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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.
 

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Sorry, I can change a fuse, but after that it’s not my field. I hope that you can find what you want, but would be surprised if someone like Sargent did not have a drop in box. They are well worth ringing to ask, this link may help;

 

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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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100ms would help but I'd be looking at seconds to be safe.
Can you go to say 2000ms?
 

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Just out of interest why did you pick the Arduino rather than say a Rasberry pi?
 

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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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I play with the PIs a bit and like them. Big community of users. But at the end of the day they are all just programmable mini cpus.
 
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