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[Unsinkable 2]

hi all, I am building an aquaponics system in my garden and would like to add a backup 12v air pump that switches on in the event of a power out. I believe I need a relay which is connected to the main power source and a 12v battery and springs into action when the power is cut. Unfortunately I don't know what exactly this relay is called or how to attach it. Can anyone help me please. Thanks in advance. U2

[kinmel]

Is the existing pump also 12v from a mains transformer ?

If so Google " 12v dc backup power supply for aquaponics " and you have many choices

[Unsinkable 2]

Hi Kinmel, my pump is a 240v and I am trying to find a relay that stays off when a voltage is detected and on when it doesn't. But I will look at you suggestion. Thanks u2

[kinmel]

Plenty of relays that use 12v to switch on 240v, I can't find one that does the opposite.

One option is to take a spur off the 240v supply and drop that to 12v DC and use that to switch the 12v pump's relay to a the battery. 

[chas]

Am I the only one who's worried by someone who doesn't seem familiar with electrics playing with mains voltage and water? I might be doing the o.p an injustice, but lack of knowledge is deadly with these things. Sorry if I'm wrong, but safety should come first.

[Shipmate60]

Check out fire alarms and burglar alarms these can have these.


Bob

[Unsinkable 2]

Ok I found a great link on YouTube that shows exactly what I need to do.


Chas. Water and electricity yeah your right, luckily the two don't touch as this is an air pump that sits in a nice dry box and just pumps air down a tube if or when the main power fails. I've had one spikey hair do, never again.


Kinmel. Apparently there is a 'piggy back' plug that plugs into the mains and the 'water pump' plugs into it. The piggy back has a wire that goes to the relay (held open by the 240v) and in the event of a power out the water pump stops and the lack of 240v closes the relay Which completes a circuit between the 12v battery and the air pump.


I wasn't sure what type of relay it was and that's why I asked you guys. Lots of knowledgeable guys here who know the wizzardry ways of electrickery. Anyway due to a new video posted the relay is now visible for all to see along with an explanation. Thanks anyway! U2


Bob, good thinking I'll check those systems to see if they have the same relay.