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I'm wanting to try some electronics trickery after many, many years away from it. Unfortunately many of the rules evade me but I feel like I could pick it up quickly, again.

My goal for my first project is this: I have a vehicle equipped with a reverse (back up) camera that shows on the LCD screen when I put the car in reverse. When I hitch up the caravan to the car, which also has a reverse camera, I'd like the input to the LCD screen to change to the caravan camera.

I know the pinout for the camera on the LCD harness, so I can easily snip that and divert the camera into a circuit, and then the output of that circuit back into the LCD screen. Both cameras are normal composite cameras (signal and earth wires). So what I want to do is somehow see that the caravan camera is now sending signal and then switch the 2-pole feed going into the LCD screen from the onboard vehicle camera to the caravan camera. Maybe I can just switch the signal wire since I could just leave the earth wires connected full-time?

In my head I'm pretty sure I can do this with transistors and a relay but I'm not 100%. What's the simplest way of approaching this? i.e. without microcontrollers? Hopefully once I get down to it, it will all come flooding back to me!

Thanks

Brett.

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Composite video signals are low enough bandwidth that you should be able to switch them with a relay. Detecting when to switch is a different animal. However, I think you may be able to get away with a simple peak detector. The video signal should have sync pulses in it that should be relatively easy to detect. So I would recommend using a peak detector with a relatively long time constant followed by a comparator and small transistor to drive the relay. It would probably be advisable to ac couple the video signal and run it through an amplifier, possibly even a single transistor amplifier, to limit interfering with the video signal.

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  • \$\begingroup\$ Thanks Alex. A bit more complex than I was hoping, but I will start googling some of those terms and see what I can learn :) Appreciate your help. Brett \$\endgroup\$ Feb 2, 2016 at 2:41

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