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I have a simple question: would I be able to send a video signal (composite) to each relay per camera? The reason is that I only have one video input but need to be able to use two cameras (not at the same time, though).

I have my drawing that I sketched out of what I think the hookup may need to look like.

enter image description here

I wasn't sure if a relay would work since I was thinking the relay itself would mess with the video signal when the magnet engages the pin inside.

I will be using this type of relay with an Arduino:

enter image description here

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    \$\begingroup\$ A better solution would be a multiplexer or bus switch ic, especially one designed for video frequencies. These are dirt cheap, solid state ics and would work a lot better than a 12v relay. You could even power them directly from the arduino instead of needing a 12v supply. \$\endgroup\$ – Passerby Aug 12 '13 at 19:52
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Composite video is very forgiving and you can definitely use relays to basically perform the same function as unplugging camera 1, and plugging in camera 2, and vice versa.

In your diagram, however, you show using two relays and a "Y" splitter, which could lead to the possibility of both video signals being active at the same time, resulting in a scrambled video signal.

Instead, consider using both throws of the same relay so that your inputs from each camera are connected to the throws, and the output is connected to the pole. In this manner, only one camera will ever be connected to the output to the PC at one time. The down side is that you will have to keep the relay energized continually for one signal (power consumption), and off for the other. (A latching relay could avoid this problem.)


Looking at your Arduino relay board, the relays appear to be SPDT (single pole double throw), so you'd need to connect the shields (ground) together. The following diagram shows this:

Camera Relay Diagram SPDT

Edit:

I removed the diagram showing a DPDT relay because I goofed up; both Camera 1's composite video pins were going to the same throw on the relay. Doh! I revised the text to be applicable to the relays you have.

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  • \$\begingroup\$ What are the 2 lines going into the output to pc? Video and power? Left being power? \$\endgroup\$ – StealthRT Aug 12 '13 at 19:05
  • \$\begingroup\$ No, sorry I should have labeled those. They represent the two conductors in a composite video signal. I've left power out of the diagram entirely. If you look at the composite video plug, there are two wires; one for data and one for ground. In the diagram, we are only routing data through the relay. Ground from both cameras is combined, connected to the output PC, and bypasses the relay. \$\endgroup\$ – JYelton Aug 12 '13 at 19:12
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Here's what I was using to switch the high bandwidth signal CX-230. You might find the one that will fit your application better. We tried a splitter on transistors, but it introduces noise. However, this mechanical one seems to work better.

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  • \$\begingroup\$ Thats the ticket. \$\endgroup\$ – danny117 Feb 15 '18 at 0:33
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I would recommend going the bus-switch direction - it is assured to work. While composite video is very forgiving - I had a solution using a SPDT for camera's in a vehicle and the specific relay i had allowed cross-talk (within the relay) between the two active signals. Now if you powered them up independently (which i could not do) it might work.

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I think using an IC for switching, such as the CD4066B, which allows switching of analogue or digital signals, should work fine for a composite signal. Use the Arduino to open or close each video feed in, the 1 IC can switch 4 different signals.

https://www.google.com.au/search?q=CD4066B&ie=&oe= the IC can be had for less than $1.00 easily.

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  • \$\begingroup\$ Welcome to EE.SE. Please take the Tour at (electronics.stackexchange.com/tour). OPs question is five years old and has an accepted answer already, although CD4066 might be a good choice. \$\endgroup\$ – winny Aug 16 '18 at 13:59

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