relay to switch between 2 cameras

I'm a bit of a novice when it comes to electronics but can follow a diagram so I'm going to attempt to describe what I'm trying to do and how I think it needs to be hooked up and hopefully someone here can guide me if I'm wrong. I researched the forums but couldn't find exactly what I was looking for so I went and read the relay diagrams. What I want to do is have a switch to control the power between 2 backup cameras. I think I can hook up the RCA connection with a Y splitter and have a single switch to toggle the power between the two cameras to change the view. If I'm understanding the way a relay works then I should hook the positive power wire from each camera to terminals 87 and 87a respectively. Then I will need to run the camera power to terminal 30 so one camera (connected to 87a) will have power when the relay is not energized. Then I need switched power with an SPST rocker switch to the coil terminal 85 with terminal 86 to ground... If I had better drawing skills I would post the pic I drew directly in this thread but it's too big so I'll just link to it here: http://home.fuse.net/iflyrv6/camera_switch.jpg Please let me know if my logic is correct. I'm new here and to electronics in general so be gentle with me

Forgot to add that this is being installed on a 2005 Ford F150. I'm also using a bullet camera and a standard Boyo back up camera but that shouldn't make a difference.

your power "in" will be connected to 30 and 87 and87a will go to the cameras, so you got it. i would put a diode across the coil terminals (85 and 86) as well for safe measure.

ckeeler wrote: your power "in" will be connected to 30 and 87 and87a will go to the cameras, so you got it. i would put a diode across the coil terminals (85 and 86) as well for safe measure.

Great, thanks! So I am correct in saying that there are 2 power sources? One for the relay at terminal 85 and one for the cameras at terminal 30? Would a 3amp diode be sufficient between 85 and 86?

You are both quite right in what you say but I'm being slightly pedantic here in suggesting 86 as the pos coil terminal, to bring it in to ISO standards (OK, C.K. I know OTT as usual) it's just that all OEM relays would be wired that way, also diode band and yes 1amp is OK to pos side of coil.

Sorry, just thought of something else, make sure your power source for the relay is ign, or acc or backup lights.  Don't make it permanent.

So Howie, switch the polarity between 85 and 86 where positive enters 86 and the Diode band towards positive (86) like this 85 ->|- 86. And, only this power (not the power to terminal 30 and the cameras) need to be to the ignition or accessories? Or both?

Yes to both your questions. Either may be ignition or acc or reverse light fed, it's just that the coil pos, 86 mustn't be permanently fed because that will flatten your battery in about 12 hours if you leave it switched on.