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I'm trying to bury cables for my garden. The requirements are to have 12v power for a water pump 30-40 watt (2.5 amp), network connectivity for sensors and a webcam. I want 4 stations at opposite corners - the maximum distance is about 600 feet to the house from a station. From what I've read maximum distance for ethernet is 100m or about 300ft.

I've also been reading about lightning surges and grounding cables. Fiber seems less susceptible to interference and lightning strikes and no 100m distance limitation like ethernet. I know once power and network connectivity is there the camera can plug into that. I'll need another cable for power to drive a water pump.

One person said use flexible PVC conduit so there are no joints underground - should I even use conduit or just buy direct bury cables?

Should I consider some hybrid network system like RS485 or something or just go with fiber?

I've read dual separate conduit if power and data but if fiber and power together in the same conduit this should be OK?

What type of wire would you use for 600 feet 12v 30-40w?

Any other suggestions as to how to achieve what I'm trying to do?

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    Direct burial is just begging to do the job over again. Run conduit and be done with the digging part (you can pull new cable if ever needed without having to dig again.)
    – Ecnerwal
    Dec 6, 2014 at 0:22
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    Fiber networking is complicated and expensive. I think it would cost you several thousand dollars to install a fiber optic network for this kind of thing. Is it really worth it to have webcams so far away from the house?
    – Hank
    Dec 9, 2014 at 3:10
  • @HenryJackson ... especially when WiFi with a directional antenna ("cantenna") can often handle that range?
    – keshlam
    Dec 17, 2014 at 4:04

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You will want to limit the voltage drop in your DC distribution wiring to 5% or less of the 12V. That would be equivalent to a 0.6V drop. An online wire size calculator suggests that for 600 feet at 3A that you would need to use 1 AWG copper wire.

Cost of that size wire suggests that you may want to consider distributing the AC mains voltage instead and converting to 12VDC at the load points. The reason being is that the amount of voltage drop in the wiring follows the amount of current through the wire. 30-40W at a line level voltage results in less than 0.5A down the wire and 5% voltage drop at 120VACrms makes room for a larger allowable voltage drop than the 0.6V at 12V. The net result is that a much more reasonable wire size can be utilized.

If you use optical fiber cables they could be in the same conduit as DC cables. You may want to separate them from AC mains cabling just because it seems like a good idea to keep AC mains by itself.

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DC voltage distribution over long distances is a pain. You have a few choices:

1) Pull big cables. Really big cables. Not really worth it. 2) Calculate the voltage drop for a reasonably-sized cable (say, 10 gauge), and sent 12V + the voltage drop at the start. This is a common approach for landscape lighting, though that commonly runs on AC, not on DC. You could do this with an adjustable power supply 3) Just send 12V down the line, and then put in a boost converter at the other end to bump it back up to the 12V you need. 4) See if the pump you are using will tolerate the lower voltage.

I like the other people who suggested wireless with a high-gain antenna.

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