Extend Nest Outdoor Camera power cable?

Hi - I need to have a very long cable run and am wondering if I can splice a wire (CAT-5 or 4 telephone cable maybe) in line with the Nest cable. Specifically, I need to add 70 feet to the cable (camera to be mounted on a pole in the back yard). The reason this concerns me is because I currently have a D-Link camera on that pole and when I spliced and added the extra wire, there was such a voltage drop that when the IR LED's came on the picture was extremely distorted. I doubled the wire gauge and it slightly fixed it but is still a terrible picture. I don't want a repeat on the Nest cam. Anyone have a long cable run like this?

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Hi,

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only

Cat 5e UTP DC resistance is 28.6 Ohms per 1000'

http://lib.store.yahoo.net/lib/yhst-9402...

Your distance is 25' Nest Cam power cable + 70' extension.

In the following scenario I am assuming that the Nest Cam power cable has the same resistance rating as the Cat 5e cable. Cat 5e is 24 AWG. If the Nest cam cable uses thinner gauge wires there may be a slightly higher voltage drop due to the increased resistance but given the short distance it will only be very small

Total distance = 190' (25+70 x 2) The x 2 is the return or loop distance, Only using 2 wires in the cable

Total resistance of wiring : 28.6/1000 x 190 =5.434 Ohms

Power requirements of camera is 5V DC 1.0A (1000mA) According to Nest Cam specifications here

Voltage drop over cable at 1.0A (1000mA) (Ohms Law E =IR) =5.434V

Therefore Supply Voltage required is 5V + 5.434V = 10.434V

Here is a power adapter 10.5V DC 1500mA that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up.

http://www.ebay.com.au/itm/1-5A-Voltage-...

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in parallel with each other and 4 earth wires are in parallel with each other), the resistance will be reduced to 1.3585 Ohms

Therefore new scenario will be:

Total distance = 190' (25+70 x 2)

Total resistance of wiring : 28.6/1000 x 190/4 =1.3585 Ohms

Power requirements of camera is 5V DC 1.0A (1000mA)

Voltage drop over cable at 1.0A (1000mA) (Ohms Law E =IR) =1.3585V

Therefore Supply Voltage required is 5V + 1.3585V = 6.3585V

The same power adapter in the link above will probably work OK when the 6V DC option is selected

Hopefully this is of some help.

Update (01/14/2017)

Hi,

Been reconsidering my statement that it will probably work OK on 6V with 8 wires in use. It may be that the voltage available to the camera (approx 4.6V after cable losses) will not allow it to operate at optimum level. Therefore I suggest that you use a 4 wire connection, 2 wires for battery, 2 wires for earth, and select the 7.5V option on the power supply. This will give you approx 4.8V for the camera which is closer to the 5V required. If neither of these work well use the 2 wire option at 10.5V this will give you the full 5V necessary. It will be by trial and error I think as the optimum voltage operating range of the camera is unknown, to me anyway.

"Hint" If you use the 2 or 4 wire option use only the coloured wires in the cable as that way it avoids confusion whether you have the correct wires connected at each end than if you use the whites as well.

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Wow! Thanks for the solution as well as a link to a suitable power supply.

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I disagree strongly with the suggestion of jacking up the PSU voltage given in this answer. Just because the current "requirement" is 1.0 A - this doesn't mean the camera is actually taking 1.0A - it could well be much less, especially during the day when the IR LEDs are turned off. If the camera is taking 0.1A then you would need to redo the calculations of voltage drop with that figure. So my guess is use the 5V supply, use all 8 conductors and it will be fine. You can always measure the voltage at the camera end of the wire in both day and night conditions to see how low the voltage is. My guess again is that the camera will work fine at 4.5 volts, though without knowing internal configuration this is not assured. Quite probably, though, there may be an internal regulated power supply which can handle low voltage somewhat gracefully.

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Anyway, the point is, you need to just be careful to measure the actual voltage with the camera connected, and to make sure whatever setup you choose doesn't put the camera out of specified operating range under either day or night conditions. IMO it is better to use all conductors, as this will give the minimum difference between day- and night-mode voltages. Ultimately, it may be necessary to put a stabilized supply at the far end of the cable (like a DC-DC converter)

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