Voltage, Current, Distance Question

[Thayne]

2KIL/CM That is 2 x 12.9 x amps x length divided by Circular mills of the wire. Please this is the interweb google it. Voltage Drop Calculator. Voltage Drop is not enforceable per the NEC.

Voltage drop is enforceable by the NEC as long as the installation is subject to NEC. (This one isn't because of the low voltage and being class 2 wiring.)

The NEC does not permit the voltage drop to be more than 5% total from the point of supply to the load--Of course this applies to the premises wiring that is subject to the code.

 

[jackj]

ipfd, he said he was going to use 10 vac because he already has that on the tower. Also, the amount of voltage drop is determined by the current and the resistance. The type of current (AC or DC) won't effect the drop.

 

[Confuzzled]

OK, here's a little more.

Mast is about 40' tall comprised of three cores of 1-1/8" fence top rail lashed together for a total diameter of a little over 3" (Think honeycomb if looking at it from the end). Guyed and grounded.

TV and Cell phone repeater antennas at the top along with the camera. 2 RG-6, rotator, camera power (4 conductor, 22AWG) and Cat5 LAN cable for camera (backup for wireless) already in place. COAXs are connected through grounding adapters. LAN cable will be tied through a lightning arrestor and grounded.

Options for camera power:

A > 10 VAC (up to 8 amp) in garage at base > 22 AWG cable up mast (maybe doubling conductors) > bridge & regulator mounted inside dome > camera.

B > 110VAC line power up mast inside PVC conduit separated from coax by at least 4" > weatherproof box housing socket w/ wall wart plugged in > camera.

I have everything to do both, but for some reason, I'm just not wild about 110 even though it would be into a GFCI at the base. I'm not sure why since I have other outside lighting and outlets. Nothing else is that high though.

I know the 7805 will put out some heat, even with a heat sink, but I don't know if it will be enough to limit/reduce frost on the lexan dome. Using the 110 option, there will be no heat source at all to reduce frost, unless somebody has another idea.

The camera shouldn't draw more than an amp even though the wall wart is 2 amp. The 1 amp limit for the 7805 should be enough, I hope.

I just can't make up my mind.

 

[petrol88]

Assuming the 10VAC provides enough current, I think I would full-wave rectify it at the top, then run the rectified power into a 5V regulated automotive power adapter (think cigarette lighter adapter) rated to handle the necessary current at 5V. Something like: http://www.amazon.com/Micca-2000mA-Power-Adapter-Slim-HD/dp/B003G8OVNA

Rectified 10V is going to be within the allowable input range for DC powered applications (usually they are tolerant to input voltages from 9VDC to 16VDC). I would make sure your rectifier circuit had good filtering to eliminate all AC components from the input.