Hey some help you could please.

I want to wire up my back up camera on a switch but also to the reverse lights so that they always come on in reverse automatically, but also with the switch whenever I want regardless of my gear. I already have it working wired to a switch, but I haven’t tapped the reverse lights yet because I’m not sure how to prevent the reverse lights coming on when I turn on the camera with the switch, since there’s only one hot wire going into camera. So as far as I know I would need a diode on the tapped wire to the reverse lights to prevent current from turning them on when switch is turning camera on correct? How do I choose such an absolute one way diode for this?

thanks

 

Why would you need to use the reversing camera when you don't intend to reverse?
All the after market version just detect when the reverse gear is selected i.e. back up lights.

 

Why would you need to use the reversing camera when you don't intend to reverse?

For the same reasons you might use your rear view mirror?

 

Yeah I want to be able to turn it on to check a boat trailer while driving, or many other situations where you might want to see behind you when not in reverse

And this is just a cheap after market unit, one hot wire going in, one ground wire, and camera feed wire

 

Yes, you need a diode connected in series with the power from the reverse lights (anode towards lights).

 

How do I choose such an absolute one way diode for this?

Verify that your camera will work with a diode drop in the power source. You can try a regular rectifier diode (e.g. 1N4001 for 1A, 1N5400 for 3A). If that doesn't work, you could try a Schottky diode that will have about half the voltage drop, but will probably cost more.

You're going to use diodes to OR your controls together.

With only 2 inputs, you could drop D2, but I wouldn't do it.

 

With only 2 inputs, you could drop D2, but I wouldn't do it.

If one input is a switch to turn on the camera, I don't see a need for more than one diode going to the backup lights.

 

Ok great thanks so much for the detailed replies. This is where the schooling starts for me as I don’t really know exactly how a diode affects the circuit.

As far as I know, the diode will block current going to my reverse lights when camera switch is on, but will allow current to flow to camera when reverse lights are on. Now are you saying there will be a voltage drop to camera as a consequence of the diode when reverse lights are on? Is it as simple as just over sizing a diode so any voltage drop would still be above camera operating needs? Not even sure what metrics to asses a diode by (like voltage/current/allowable pass through etc?)??

thanks again

 

As far as I know, the diode will block current going to my reverse lights when camera switch is on, but will allow current to flow to camera when reverse lights are on.

An ideal diode would only allow current to flow in one direction. The diodes I mentioned aren't ideal, but the reverse leakage current won't be of consequence. They also have no forward voltage drop.

Now are you saying there will be a voltage drop to camera as a consequence of the diode when reverse lights are on?

Normal rectifier diodes will drop about a volt. It varies by forward current. Schottky diodes will drop about half that.

Is it as simple as just over sizing a diode so any voltage drop would still be above camera operating needs?

You're limited in diode "sizes". I'd be surprised if your camera wouldn't operate at 11V, but it's always a possibility. My wireless 12V security cameras are spec'ed to operate down to 9V.

Not even sure what metrics to asses a diode by (like voltage/current/allowable pass through etc?)??

What matters is the maximum current your camera can draw. I mentioned rectifier diodes that are rated at 1A and 3A continuous forward current.

 

Since you normally operate the camera when the engine is running where the battery voltage is likely well over 13V, I don't think the voltage drop of a standard diode will keep the camera from operating.