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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, June 01, 2021 03:06 PM
Hobby Circuits List
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More Remote Circuits;
Camera Circuits;
Television Circuits |
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Remote TV
Camera Power (July 4, 2011) |
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while back I received an email from a company with a problem. They needed a security
camera installed at some remote location. The camera was a high quality color
camera sending out standard NTSC video through a long 500 foot 50 ohm coax cable.
With some difficulty they got the coax strung. They were told that there would
be AC power near the camera location to power that device. But, they then
learned that in fact, there was no power available. They thought about using a
solar panel and a battery but they decided to call me for help instead. Was
there some way to power the camera without stringing another cable? |
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The circuit below is what I suggested they use. It uses an old
trick of mixing DC to run the camera with the video signal. Two coils are used to
isolate the two signals. One coil allows 15v DC to be injected into the 500 foot
long cable and a second coil pulls out the voltage, which is fed to a low voltage drop
12v regulator. With a typical 6MHz bandwidth, the impedance of the coil would be
high to the video signal but would have a low DC value to the power supply. The camera
requires a clean 12v and pulls about 300ma of current. I suggested at 15v power
adapter with at least a 400ma current rating. |
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Click on Circuit Below to view PDF of Schematic |
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