Missing in the discussion is the non-trivial resistance in the cable...
24Ga wire is variously reported at about 0.025 ohms per foot. 1000' down
and 1000' back and you have 50ohms of added resistance to the circuit.
If I'm reading your description right, 130mA for the camera and 50mA for
LEDs, 50ohms*180mA, you'll be loosing 9 volts to the cable alone. I'd be
surprised if this works at all. Probably getting by at the moment because
you're only using 320' of cable and doubling up the pairs - which cuts your
cable loss to about 1.5 volts.

I'd recommend increasing voltage and putting a switching regulator on the
end.

I tripped on this one the other day
http://www.mpja.com/LM2596-Step-Down-Adjustable-15-37V-DC_DC-Converter/prod=
uctinfo/30148%20PS/
Probably
not the "best" depending on your metrics, but rates high in the "easy",
"cheap for a one-off", "small enough" and "available off the shelf"
categories.

-Denny



On Sat, Oct 19, 2013 at 7:33 AM, RussellMc <apptechnz@gmail.com> wrote:

> LEDs should (~~=3D must) be driven by constant current.
> Trying to drive them with ~=3D their notional Vf will lead to a substanti=
al
> variation in most cases.
> When operating on 12V you should have only 3 LEDs in series, plus current
> control..
> When operating with 24V you can have up to about 6 LEDs in series plus
> current control.
> The more "headroom (aka spare voltage) that you have the easier it is to
> get ~=3D constant current with simple circuits.
>
> It is exceeding bad practice (also exceedingly bad practice) to attempt t=
o
> drive two parallel strings of LEDs without any attempt to current balance=
..
> I have seen some LEDs that are so well matched for Vf that you could
> 'almost get away with" doing this, but most LEDs have enough variation,
> even in the same batch, to make this problematic.
>
> LEDs should be driven at MORE than their rated combined Vf with a constan=
t
> current source taking up the difference. You can use as little as an LM31=
7
> and one resistor as a constant current source.
> You'll need about 3.5V "headroom" for an LM317 to operate as a current
> source.
> eg for 4 LEDs. V min ~=3D 3.8V x 4 =3D 15.2V.
> Headroom =3D 3.5V say.
> Vinmin=3D 3.5 + 15.2 >=3D 18.7V.
> ie ~=3D 24V would be dandy.
>
> Vin =3D LM317 Vin
> Iout =3D LM317 ADj.
> Rcc from Vout to Vadj.
> Rcc =3D 1.25 / I A =3D 1250 / I_ma
> Dissipation in R =3D~ 6/R or 1.25 mW  per mA
> eg for 25 mA.
> R =3D 1.25 / .025 =3D 1250 / 25 =3D 50 Ohms.
> Pd_Rcc =3D 50 x 1.25 ~=3D 63 mW.
>
> If you have 4 LEDs in series and this is unchangeable, you could short on=
e
> out per group and probably get a better result.
>
> If these are on only occasionally then 'any brand will do", almost. If th=
ey
> are intended to spend thousands of hours on over their lifetime then you
> should use LEDs from the major LED manufacturers OR ones made under licen=
ce
> to them. LED lifetimes are still woefully low in many cases - despite
> claims to the contrary.
>
>
>              Russell
> --
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