As part of my down the hole natural gas well inspection camera, I have=20
an array of bright LED's. Currently I'm supplying 12 VDC via a generic 1=20
amp 12 VDC power supply to a pair of composite (yellow) video (2 pair)=20
balun and power supply (2 pairs) to Cat-5. The Cat-5 length is 320', but=20
could go to 1000'. Down hole is another balun, a minature color standard=20
definition camera and an array of LED's. The LED's are configured as 2=20
parallel strings of 4 serial LED's. The camera has a 8 - 12 VDC power=20
required, and at 12 VDC the LED's are not as bright as they could be.=20
Here's a list of the equipment:

Generic 12 VDC power supply
TV camera  8 - 12 VDC, 130 ma.=20
http://www.mcmelectronics.com/product/82-13296
Video to CAT-5 Baluns http://www.mcmelectronics.com/product/50-7745
Array of LED's NTE30071,   10mm, Vf =3D 3.8 v max., Vr =3D 4 v max., If =3D=
 25=20
ma Max.   http://www.mcmelectronics.com/product/NTE30071

My proposed solution is starting at camera power supply:
Camera
LM7812 12 volt voltage regulator to protect camera from over voltage
LM317 Adjustable voltage regulator to protect LED's from over voltage,=20
set to maximum LED allowed voltage
Baluns, for power it's straight through with 2 pairs of the CAT-5 with=20
320' (could be up to 1000') CAT-5 between
LM317 adjustable voltage regulator with variable resistance to adjust=20
LED's brightness
24 VDC 1 amp power supply

Several questions:
1: Can I drive the LED's slightly less than the series Vf =3D 4 * 3.8 VDC=20
=3D 15.2 volts reliably, say 14.5 VDC
2: With the 2 parallel strings of LED's, can they be depended on to=20
share the current equally? The LED's would be same part number, but may=20
not be same batch. Or could they overload one of the strings causing an=20
outage.

The configuration of the LED's is fixed, but not changeable (a bit of=20
work and buy new LED's)

Any comments appreciated.

--=20
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