240V DC to switch on 12V

Discussion in 'The Projects Forum' started by Mariusnotoey, Mar 3, 2016.

  1. Mariusnotoey

    Thread Starter New Member

    Mar 3, 2016
    2
    0
    Hi,

    I'm in the need of something to switch on a 12V light and horn when a 240V DC circuit trips. This is to give an alarm telling us we lost the 240. I guess it will need a 12 V condensator or battery to power the light and horn. A condensator would be great so that we dont have to worry about batteries. Could a condensator power a rotating light for 30 min? Like the ones on a truck. This unit will need to be connected in line with the 240. There is no other power source to feed that light either.
    Thanks,
    Marius Notøy
    Norway
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
    all you need is a 240v dc relay to detect mains fail, and a 12v battery to feed the horn/light .
     
  3. Mariusnotoey

    Thread Starter New Member

    Mar 3, 2016
    2
    0
    Thanks, Any suggestions on a relay? Dont know what to look for.
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,974
    744
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