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Cheap Relay for 12V based backup system. Safe for ALL of us.
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Author:  skygazer [ May 9th, '08, 11:58 ]
Post subject:  Cheap Relay for 12V based backup system. Safe for ALL of us.
Just purchase a cheap $6.20 AUD relay from Jaycar http://www.jaycar.com.au/productView.as ... &SUBCATID=

Basically I am using an on mobile phone charger to power the 12V relay. Whilst on the power keeps the relay open, when the power cuts, the relay is closed. Put this inline with your 12V battery based backup (Battery powered airpump, or 12V pump) to automatically turn it on.

The outer left and right lugs should be connected to your old phone charger, the middle pin and top pin, inline from battery to backup solution.

hope that helps someone else.

I am starting with a $10 battery powered air pump, until I decide on my final solution. (Better than nothing I hope - BOYU 2L/min).

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Author:  Hamish [ May 9th, '08, 14:27 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of us.
Nice idea! I paid about $90 for my backup switch. Sure it was a plug and play device - but this is just as good! Well done!
Author:  Delgrade [ May 9th, '08, 14:54 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
how sumple :P

cheers for that
Author:  steve [ May 9th, '08, 15:25 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
LOL! Right on!

here we are re-inventing the wheel!

and those contacts are rated to atleast 20A at 12VDC
Author:  EllKayBee [ May 9th, '08, 17:01 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of us.
Close Steve 20/30A :lol: ...2nd last on the page
http://www.wittrin.com/englisch/produkte.php?id=2
Author:  steve [ May 9th, '08, 17:29 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
C4,c5 or c6 diagram on that page is the configuration that people want to look for
Author:  Jaymie [ May 9th, '08, 19:26 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
would this work going through an inverter? Should I show my brother this thread?
Author:  steve [ May 9th, '08, 19:40 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!JAYMIE!!!!

thats the same system i suggested at the start (except for using a 12v coil and a phone charger)

but NO, that relay is no good as the contacts are not rated at 240v i dont think.

but there are ones that are, and are a dime a doz
Author:  bundaberg kid [ May 9th, '08, 20:09 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of us.
:) good n chunky relay, mostly used when you add driving lights to ya car...or airhorns
Author:  Jaymie [ May 9th, '08, 20:12 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
now Steve, you KNOW I said when I first brought this up that I know NOTHING about electicklery
Author:  bundaberg kid [ May 9th, '08, 20:19 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
steve wrote:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!JAYMIE!!!!

that relay is no good as the contacts are not rated at 240v i dont think.




???? does that really matter? Its the contacts your talkn about not the coil yeah?

it doesnt really matter what the contacts are rated at...esp @ 20-30A
Author:  steve [ May 9th, '08, 20:50 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
yeh, i was talking about the contacts, but from memory those relay amp ratings are de-rated baldy at higher voltage and i think thye only go to 120 or so, but might be wrong
Author:  bundaberg kid [ May 9th, '08, 21:02 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of us.
yeah but wouldnt there be a lower current draw on 240V as apposed to 12V given the same load?
Author:  jazzplayermark [ May 9th, '08, 21:19 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of us.
That's a great relay Skygazer. I just designed a circuit for a battery backup/low level detector that uses one very similar. Mine is an automotive relay. I believe yours is also. They should pretty much last forever and the contacts are heavy duty. Whatever kind of pump you run, this is a good solution.
Author:  gokul [ May 10th, '08, 17:48 ]
Post subject:  Re: Cheap Relay for 12V based backup system. Safe for ALL of
Yes, there would be 12/240 th of the current draw for the same load, so it could gladly be used.
But such a high current rated relay is overkill for 240V, you could buy cheaper ones for 240V, as the 240V load has a correspondingly lower current draw.
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