I've tried searching the web, but so far can't find any real help, so if there's any wiring geniuses on here who can help me I'd greatly appreciate it!

Here's what I'm trying to do: I've got a headunit that switches to camera input when it sees 12V on the purple camera signal wire. I've currently got it working wired up to the backup lights so that when I shift to reverse, the backup camera gets power, the input signal is triggered, the headunit switches display and all is well. However, I'm wanting to add a front camera (to keep from scraping curbs with this low front end), and be able to

A) have it operate with the reverse lights like it does now

B) when I move the rocker switch backwards, it will signal the reverse input on the headunit and power the reverse camera until I switch the rocker back to neutral

C) when I move the rocker switch forwards, it will signal the reverse input on the headunit and power the front camera until I switch the rocker back to neutral.

I'm not a wiring pro, but I know enough to be dangerous. I've drawn up two options that I think might work, one with diodes (which would be easier to wire) and one using relays. Can someone look these over and tell me if I'm missing anything, if I can simplify anything, or if there's an all together better way to do this? Also, if the diode method here works, I'm not sure exactly what diodes I would need to purchase. Any help is greatly appreciated!

Relay Option:


Diode Option:

 

I don't read schematics but couldn't you:

Wire the rear camera just like you have it, triggered by reverse lights.

Then install the front camera, connected by a simple switch that both applies power (not from the reverse lights) to the front camera and the purple trigger wire.

The head unit should switch when that happens.

Just an idea.

 

Yeah, I wish it were that easy, but I'm afraid that 12v would leak back into the reverse lights and the power to the rear camera... which would put 2 video streams on the rca input line, so it wouldn't display right, and possibly light the backup lights. That would work if I put an interim switch between those 2 inputs on the purple input wire, but really hoping to make it work more slick than having multiple switches to hit.

 

What if you ran the front camera through the video in and a switch to turn it on and leave the rear camera connected as design. This would eliminate the use of so many relays and you would won't get any video interference.

 

I guess I'm missing something here. Does the head unit have two video inputs? One for front and one for rear cameras? If not, how are you addressing the video signal switching?

From what you describe there is only one wire (purple) that commands the head unit to go to camera/video mode. This needs to happen no mater what camera you are viewing? Powering this and the rear camera is being done with your backup light connection. Now you need to power this command line and switch/select the the camera (video signal) you want.

So I'm a little hung up on a video switch if it is not done in the head unit. Say video 1 or 2.

If it is a single video input to the head unit, then I think you need a video switch. Look for one where there is a NO (normally open) and NC (normally closed) ports. The NO port would be your rear camera, and this switch would be controlled by the reverse lights, like you have. NC would be front camera. Now all you need is to power both cameras and the head unit command with a switch when you want video on. Then if your are not in reverse then you will have the front camera.

I could draw a picture but don't know how to post. But might try if you want. Search the net to see if you can find a video switch that operates off 12 vdc.

 

Video switching has to be addressed somehow and this is a very elegant (and much simpler) way of doing it.

 

One video input, planning on using a Y adapter... which shouldn't be a problem assuming only 1 camera is on at a time.

Yes, purple wire forces it to switch to the one rca video input I described above. Right now the rear camera is only powered when the backup lights are on, but on what I drew above it needs to also power on when the switch is pushed to the back position.

Unfortunately, I sure can't seem to find a 12v rca video switch anywhere, which is why I was leaning towards this method of only powering the cameras when they should be on. But if I did find one, using the switch method on the 12v purple input line would still kill the ability for it to still auto switch when the backup lights were on, wouldn't it?

 

I found a video switch for you. This is an A/B switch with 12 vdc switching. I'll try the link.

http://www.monstermarketplace.com/ca...-toggle-switch

If this link did not work then, Accelevision AVS200 Dual Source A/B Audio/Video Input Switcher is the name of the switch. Search on that. About $40. Finding a switch was not as easy as I thought. I'd checkout Radio Shack also.

The control to this switch looks like the red wire. So maybe the A port is NC and the B port is NO. So now all you have to do is wire the camera videos to these ports. Then use your reverse lights scheme you are using to select the rear camera.

After than you can wire up a switch (cameras ON) to just select power to both cameras (or each individually) and enable the head unit when you want video. I guess you can get as fancy as you want for that, fused and what ever.

 

Awesome, nice find. I don't know why I had so much trouble finding one. Thanks!

 

I just did exactly what you are working on.

My Electrical Engineering friend helped me diagram it and it came out pretty slick. We found it was easiest to use a DPDT relay and a single switch. Both you can buy at radio shack.

When the switch is open, the rear camera comes on when in reverse, when the switch is closed, the front camera pops up. RL is reverse light power, using a volt meter I found there was only around 9.5v power to the rear lights when they are turned on, which was not enough to power my reverse cam.



Hope this helps!! Should save you some cash, the DPDT relay was $10, make sure to get the 12v one and not the 110v one (they look identical).

 

Your welcome. It took me a while surfing through all kinds of stuff. Not as easy as I thought it might be. There is a company Periphial or something like that, that makes car stuff to interface MP3's to standard car radios and stuff. I would surf them as well to see if they have something in a video switch also.

I would also pay attention to the current draw of the A/B switch, head unit control line, and the cameras too. I have no idea how much current these draw. Your backup lights should draw more current than all of them. I would run a in line fuse from the power source to the switch that I called Cameras ON switch. I would also recommend companies like Newark electronics, Allied, or Mouser Electronics to buy wire, fuses and stuff like that. The audio and car stores charge about 100 times more for stuff. You would be surprised the markup.

Good luck.

 

That's brilliant, thanks! I appreciate the suggestion of the 12V AV switch before, but this should be much cheaper!

 

IMHO, I still think KenShores' solution is more elegant. If correctly executed it provides both, video and power switching, which is a better implementation. Of course, it costs more because of the video switcher...

If you want to go Morlok's way, let me just highlight that the Rear Cam is powered at all times except when you select the Front Cam.

To avoid having the Rear Cam unnecessarily powered you can modify it like shown in the first part of this drawing, or if you want to go a step further and isolate all this from your Reverse Lights circuit, then take a look at the second part.

 

Now I'm starting to wonder how many out there would want a device to do this. I was thinking of a 4PDT relay (which are cheap) but can't tell how well it would pass a video signal without loss. So then I looked at a RF switch/relay ($10). It would be easy enough to make. But now I'm thinking little circuit board, RCA connecters, the whole nine yards. Most of the costs would be in RCA connectors.

The video switcher I found might be the cheap way out at $40.

If the 4PDT relay can pass a video signal without much loss, then this would be the cheap way too. Once again most costs would be RCA jacks. Oh well I just got to thinking too hard on this one.

 

You make some good points and some accurate corrections.

My diagram is overly simple. I did not include the relay back at the reverse lights. On my setup, the rear camera is not always powered on, the +12 powers a relay that is switched on when the car is put in reverse, which would end up looking a lot like your bottom diagram. Do you think it would be a problem to leave the rear cam powered on? Would you "wear out" the camera?

I understand why you want to put a video switch in, but it is really just extra hardware. It is impossible for the two cameras to be powered at the same time, and even if they were, the worst you would get would be a snowy screen.

 

Without a doubt, your solution delivers the intended results with the undeniable appeal of being simple and inexpensive.

How far someone would be willing to go in the pursue of quality is a personal choice. Everything is a compromise and at the end it is a matter of choosing what makes the job done at a level that's comfortable for the user (the eternal fight: quality vs cost ).

You mentioned that when you did your installation you were able to identify a factory relay that allows you to power the rear camera only when needed. That's a very good detail because it is a component less in the shopping list, while still addressing my comments. Leaving the rear camera always on serves no purpose and it is a waste of its expected hours of life at a minimum. In addition, isolating different circuits, whenever possible, is always a good practice (you reduce the potential gremlins ).

Using a Y adapter to feed the video from the 2 cameras to the Head Unit is probably not a big deal in this scenario, as long as only one camera is powered at any given time. A videophile hometheater would be another story...

What happens is that the active camera could be overloaded, resulting in video degradation. The active camera now has to simultaneously feed 2 loads: the Head Unit and the inactive camera (please, note that they are effectively in parallel). To what extend this could be unacceptable falls into "beauty is in the eye of the beholder" category . With a video switcher, this is no longer an issue. It is definitely the proper way of doing it.