relay to switch between 2 cameras

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=113044
Printed Date: July 27, 2025 at 3:09 AM

Topic: relay to switch between 2 cameras

Posted By: p40whk
Subject: relay to switch between 2 cameras
Date Posted: April 10, 2009 at 7:29 PM

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:

https://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 posted_image

Replies:

Posted By: p40whk
Date Posted: April 10, 2009 at 7:31 PM

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.

Posted By: ckeeler
Date Posted: April 10, 2009 at 7:41 PM

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.

Posted By: p40whk
Date Posted: April 10, 2009 at 7:51 PM

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?

Posted By: ckeeler
Date Posted: April 10, 2009 at 7:56 PM

yes, 85 will be the terminal that switches the relay and 30 is the terminal that supplies the power to the cameras. 3 amps is more than plenty. if it was mine i would just use a 1 amp diode.

Posted By: howie ll
Date Posted: April 11, 2009 at 4:09 AM

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.

Posted By: howie ll
Date Posted: April 11, 2009 at 4:11 AM

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.

Posted By: p40whk
Date Posted: April 11, 2009 at 8:49 AM

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?

Posted By: howie ll
Date Posted: April 11, 2009 at 9:29 AM

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.