Avoiding DC voltage drop for surveillance cameras over long distances

Question

Trying to power 2 HD-TVI cameras 800 ft away from my home office.

The wall mounted adapter provides 12v DC at 1 amp. I am looking for a good solution at the lowest possible cost.

There are already some great answers posted for a 5v camera. This, however, involves at least 2 cameras at 12v and the wire will run in the ground.

It seems Ignacio Vazquez-Abrams and others have simple solutions by running 24v or 48v and a regulator module just before it attaches to the camera. The best answer does seem to be: distribute higher voltage and use regulators at the far end. I am not sure how to do that or what to use or if it will work?

10 gauge wire would likely solve the problem, but I would like to use the 20 gauge wire I already have.

There is not power 800 ft away at the location being monitered.

Answer 1

Wire has resistance. According to Ohms law, V=IR. Assuming your cameras use the maximum current allowable by the supply, I = 1 Ampere. Your wire resistance will depend on the gauge and metal used. Assuming good quality copper wire at 20AWG, you are looking at 10.15 Ohms per 1000ft. Lets assume you use 1600ft exactly - 800 there, 800 back. This is approx 16 Ohms.

V = 1 Amp x 16 Ohms = 16V.

Oh dear, you have dropped more voltage than you can supply!

Increasing the wire gauge to 10AWG brings the resistance down to ~1 Ohm per 1000ft, ergo

V = 1 x 1.6 = 1.6V

But wait, what if you bundle 10 seperate 20AWG wires?

V = 1 x (16/10) = 1.6V

If you have 16000ft of wire, that is.

The cameras may not run at a voltage lower than 12V, so even this could fail. However, they could also draw significantly less current than 1A, which would mean less voltage drop.

Some testing on your part would be advisable.

Edit: A simpler solution would be to use a mains extension cable and bring the 12V adapter closer to the cameras.

Wire gauge source: http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/wirega.html

Answer 2

When installing a mains extension in conformance with electrical code a specific type of wire and minimum size may be required. A ground fault interrupter may also be required. The depth of burial may also be dictated by code.

With the wire you have at 24 or 48 volts, electrical codes may not be an issue. However the size and type of wire should be suitable for burial for a reliable installation. The type of wire used for low voltage outdoor lighting and garden irrigation control should be suitable.

The low voltage feed could be either AC or DC. Both AC and DC converters can be found for a variety of input and output voltages. Most will tolerate a wide input voltage variation, so you don't need to worry to much about exactly what voltage you have on the far end. However you do need to do the math and check the specifications.

Be assured that either approach will work, but you will need to do the shopping and add up the cost.