Re: CCTV Video issues

["Doug" <not@xxxxxxxx>]

Here is what I have seen in the past, its not so much that the power supply
can't provide enough power, nor that the cable runs are so long that there
is excessive voltage drop, but rather there is some sort of interference
between the power and the video ground when powering multiple 12 VDC cameras
from the same source. My experience has been that it occurs more when the
cable runs are of greatly differing lengths. I believe it has something to
do with the video ground and negative being common at the camera, but at the
head end the video ground is probably tied to the chassis of the DVR and
then to an electrical ground, while the power negatives are all common, but
floating with respect to ground.

Doug
--

"S. Smith" <ChaosLogicXIII@xxxxxxxxx> wrote in message
news:1168735420.431346.97900@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Doug:
>
> I agree that this could well be a power issue.  My confusion comes from
> the distortions showing on both the closest and the furthest indoor
> 12VDC domes.  The closest shows no power drop while the furthest shows
> a drop to 11.5VDC.
>
> Roland:
>
> I wasn't aware that breaker protected power sources were available.
> We've always used fuse-protected power supplies.  That same in this
> case.  I will take your advice on the camera-by-camera viewing to check
> for ground faults though, it's something I'd forgotten about.  As far
> as the CM1 & CM2, I'll let my boss decide, it's his money. ;)
>
> Nick:
>
> We did the voltage calculations before we started and although we are
> close to the 4 amp capacity of the power supply, we aren't going over.
> Besides, the distortion is only seen when viewed from the DVR, not at
> the camera itself.  If it were a power issue, wouldn't it be evident on
> both ends?
>
> Matt:
>
> I will double check the baluns as per your suggestion, but I'm pretty
> sure we go them straight.  Solid color to +, striped to -.  The only
> dual voltage cameras we have on the system are the "box cameras"
> (Panasonic, lens sold seperately, gotta put it in an outdoor enclosure)
> and they are working wonderfully and presenting the best pictures.  One
> is even further out than the furthest dome (which is the one that looks
> the worst).
>
> haptictz:
>
> You seems to know a thing or two I don't.  For instance, what is
> voltage peak-to-peak, how do you measure it, and what kind of readings
> am I looking for to indicate good, bad, or otherwise?  And for your
> last question, no.  Fully half of the domes are mini-domes that can't
> be that expensive while the others are fancier tamper-proof kind with
> varifocal lenses and fully articulating inner mountings.. (very nice,
> probably $200 a piece)  Would mis-matching NTSC and PAL generate this
> kind of effect?
>
>
> Thank you all for you input and look forward to hearing more
> suggestions.  I won't be tackling this project again until next week,
> but I'll be sure to let you know how it goes.
>