Date: 8/02/2016 12:36:53
From: CrazyNeutrino
ID: 843638
Subject: 240V Switch to 12 V

Im after a switch that can switch between 240v and and 12 volt battery

is there any thing available that can do that

Not an UPS

I have a modem with 12V dc
it has a 240V to 12V adapter
I want a switch that can detect power lose from the 240V adapter and switch over to the 12V battery

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Date: 8/02/2016 12:45:36
From: sibeen
ID: 843648
Subject: re: 240V Switch to 12 V

Relay with the coil driven by the adaptor. The mains fails, the relay switches over. Mains returns and it switches back to adaptor power. Will have a short break during the switching cycle.

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Date: 8/02/2016 12:49:33
From: CrazyNeutrino
ID: 843650
Subject: re: 240V Switch to 12 V

Are there any circuit designs on the internet

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Date: 8/02/2016 12:57:47
From: CrazyNeutrino
ID: 843655
Subject: re: 240V Switch to 12 V

sibeen said:


Relay with the coil driven by the adaptor. The mains fails, the relay switches over. Mains returns and it switches back to adaptor power. Will have a short break during the switching cycle.

Thanks sibeen Ill have a look around on the Web

Id rather buy something off the shelve its its available

If not I’ll tinker around

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Date: 8/02/2016 13:06:56
From: sibeen
ID: 843656
Subject: re: 240V Switch to 12 V

Crazy, just ensure you put a diode (In4004 etc) across the coil in reverse polarity. This will stop a kickback from the coil when de-energised and stop the 12V adaptor blowing up.

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Date: 8/02/2016 15:42:24
From: CrazyNeutrino
ID: 843755
Subject: re: 240V Switch to 12 V

ok thanks for that

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Date: 9/02/2016 12:08:20
From: fsm
ID: 844212
Subject: re: 240V Switch to 12 V

You could connect permanently to the battery with a trickle charger connected to the 240v mains to keep the battery topped up. If the 240v goes out then the battery will simply keep supplying power until it goes flat or the mains comes back.

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Date: 9/02/2016 18:46:23
From: Jing Joh
ID: 844350
Subject: re: 240V Switch to 12 V

CrazyNeutrino said:

I want a switch that can detect power lose from the 240V adapter and switch over to the 12V battery

It’s called a UPS

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Date: 9/02/2016 21:43:01
From: wookiemeister
ID: 844409
Subject: re: 240V Switch to 12 V

unless you have some kind of training i advise against building your own circuits that will plug into the 240 VAC

you can create something that can catch on fire

give someone a shock or kill them

if i were you i’d go for a UPS that meets your needs, you might even find one that pumps out 12V DC and / or 240VAC

unless you know exactly what you are doing don’t mess with 240VAC

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