looking for a relay
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Logistics Pro
Joined: Feb 2000
Posts: 3,955
Likes: 50
From: Mesa
looking for a relay
I would like to find a 12v relay that is hot when the power is off and off when the power is on. Backwards of a normal relay. Know what I mean? I'd like to have an item on while my truck is parked and have it go off when I start/drive. Any ideas? Thanks.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
You can do that with a standard SPDT relay. Take a look at the schematic:
When the relay is OFF, 30 is connected to 87a. When the relay is ON, 87a goes open-circuit. You would leave 87 unconnected for what you're doing (note that it will be hot when the relay is ON).
When the relay is OFF, 30 is connected to 87a. When the relay is ON, 87a goes open-circuit. You would leave 87 unconnected for what you're doing (note that it will be hot when the relay is ON).
Moderator
Joined: Jan 2001
Posts: 57,012
Likes: 2,750
From: Virginia
You may find most of the relays on the shelf are 4 pin types that will not do what you need. Some of them do not have the 87a terminal. Just keep hunting till you find one that has 5 terminals with the 87a terminal.
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