rear view cam auto switching - would this work?

Im going to be setting up a rear view camera where the video output is sent to a VGA switch box. When the reverse lights go on, a relay is powered and the switch to switch video inputs on the vga box is triggered.

Now I want to also add a manual pushbutton to engage the rear view camera when the reverse lights are not on.

Would something like this work?

http://www.dwoloz.com/revcam-diode.png

I really have no electronics background and do not know how to use diodes properly really but from my limited understanding wouldnt the above be the proper use?

Should work just fine.

Why are there two lines going to the VGA box? Are you seperating a line to make the switch?

That relay is going to be energized all the time and not work as a swtich. With a constant 12v to 85 and constant ground to 86 it is just going to stay energized no matter what position the reverse light is in. I can not see how that really is going to work.

Let's say your VGA box needs a 12v positive line to change inputs. Then you should wire 85 to the positive on the reverse lights and 86 to ground. 87 would go to an ignition positive line and 30 to the VGA box. Then you can add a switch, connect the switch positive output to 87a and you can turn the cam on whenever you like. But I am not sure how the VGA box works...what do you need to make it switch?

I think the constant 12V is where the switch/button is. So the relay is not energized until either the reverse lights go on or the button is pressed.

LK is correct
The smaller blue box is a switch (as stated in my post)

Ok my bad...somehow I missed that because your post states that you want to add a switch not that there is a switch in your diagram.The way your little blue box is drawn is what confused me....I thought it represented the battery not a switch. No big deal. I would still like to know how the VGA box works though. I am asking because I will need to make something like this.

All the VGA boxes work differently but the one I want to get is one that requires you to press a non momentary pushbutton to switch video inputs then release the pushbutton to switch back. The cheesebox does this and the member here eCar was the first to suggest it

Post the supplies you get for this, I'm interested to do the same!

First I need to really be sure the diode placement is correct :p


Supplies are basic though:
SPST relay(or a DPST with only one pole hooked up) http://www.radioshack.com/product.as...5Fid=275%2D226
SPST switch (rocker, toggle, pushbutton, etc) http://www.radioshack.com/product.as...t%5Fid=275-617
Diode of some type (1N4001 I guess) http://www.radioshack.com/product.as...%5Fid=276-1101
Cheesebox or other VGA switch box (seems like no one sells the cheesebox anymore, its discontinued)

So what you are planning on doing is jumping the push button across the relay....gotcha. This is something I am researching also before I purchase anything for my computer. I am using two cameras in my car now and want to keep them with the new setup.