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Thread: Fire siren project, relay help needed.

  1. #11
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    Quote Originally Posted by Shadow View Post
    12v at both relays with a drop in amperage, compared to running a single relay, correct?
    Nope. Two relays in parallel will draw twice the amperage of one relay.

  2. #12
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    really? interesting.. always thought it was an amperage drop because the single +12v supply can only feed so much
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  3. #13
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    There would be 2 12v sources. The first is a low amp switching signal from a toggle. The second would be a fused direct source from the battery using like 10ga wire. The Toggle source only activates the relay, it doesn't power whatever accessory. Then the 12v output (12v from bat) goes to said accessory. And of course there is the ground for the relay. If you picked up a 30amp 5 blade relay, then you would only need 1 as there are 2 12v output blades. Mount the relays some what close to where you have the sirens mounted. You won't but a little amperage drop/loss that way and almost a full 12 volts to the sirens.
    Wire size and length plays a big role in amperage loss
    Last edited by 1BadBird; 09-24-2011 at 07:33 PM.


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  4. #14
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    Quote Originally Posted by 1BadBird View Post
    There would be 2 12v sources. The first is a low amp switching signal from a toggle. The second would be a fused direct source from the battery using like 10ga wire. The Toggle source only activates the relay, it doesn't power whatever accessory. Then the 12v output (12v from bat) goes to said accessory. And of course there is the ground for the relay. If you picked up a 30amp 5 blade relay, then you would only need 1 as there are 2 12v output blades. Mount the relays some what close to where you have the sirens mounted. You won't but a little amperage drop/loss that way and almost a full 12 volts to the sirens.
    Wire size and length plays a big role in amperage loss
    ^^^^^ this ^^^^^
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