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Arduino Relay? Answered

I'm working on a UPS of sorts for an arduino project of mine. Basically if the pwoer goes out I want the arduino to switch to a 9v battery backup. I was wondering what sort of relay I should use and if a transformer would be needed. Ideally I'd like to use a simple power supply with a transformer built in and then have that feed into the relay, but I'm not sure if the 7-12v from a normal arduino power supply would then be enough to switch the relay (normally closed).

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user
iceng (author)2015-06-29

Here is your automatic and instant switch over schematic.

You could even add a resistor from the 12vDC supply to trickle charge the 9vDC Batteries.

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user
iceng (author)2015-06-28

If the pwoer goes out so will any PS and most transformers.

Just use a diode from the 9v to take over when the higher voltage stops.

This will happen instantly compared to a relay.

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user
FarmerKJS (author)2015-06-28

I would have it on all the time in case the sump fails.

You will have to experiment a little to see if it will reboot.

It could probably send an email pretty quickly... Depending on how it is programed

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user
FarmerKJS (author)2015-06-28

Just a simple 5 pin relay. I will add a schematic as soon as i draw it

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user
FarmerKJS (author)FarmerKJS2015-06-28

If its unclear just ask for clarification.

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