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- A number of considerations need to be made when designing
a cctv system. Power requirements, distance, cabling to name
a few...
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- Single Versus Multiple Port
- If you are running a single camera, or maybe 2 camera security
system, it is probably more cost effective to purchase a single
power supply adapter for each camera. Up to 4 single camera supplies
off of a power strip may work when you are designing this type
of system, but neatness may count for something as well. A single
power supply box offers an effective, attractive solution for
multiple camera power.
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- DC or AC CCTV Power
- CCTV and security systems have until the last 10 years been
primarily 24VAC. Advent of smaller, more compact and covert cameras
has resulted in an increasing number of 12 volt DC installations.
Both are lightly regulated (low voltage) for construction allowing
flexible securty and surveillance installations, and each has
its advantages.
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- 12VDC requires a smaller footprint for a camera because it
does not require a built in rectifier. though originally adopted
for covert camera applications, it became popular for larger
C/CS cameras as it lessened the manufacturing costs. 12vDC is
NOT good for long cable runs however, and some 12V DC power supply
boxes are more costly than their 24V AC counterparts. Also, for
some time the 12V DC powered camera was shunned by many professionals
because it was hard to get "in phase" when installed
in a Multiplexed video system. Current Digital video recording
has all but eliminated this problem.
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- 24VAC Power supplies are often simple transformers distributed
into multiple ports, or used singly. Advantage is cost in multiple
port systems because of reduced components. 24VAC power performs
better over long runs with less need for heavy gauged wire runs.
Most, but not all outdoor housings which have blowers and heater,
require 24VAC. The power consumption is better handled with 24VAC
as well.
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- Often, mixed systems exist where both types of cameras are
used. Newer12V DC camera addtions to established 24VAC systems
can be accomodated with the use of power converters. These are
simple devices which regulate a 24VAC voltage to 12V DC. Sometimes
the 24VAC to 12VDC power converter is used when sending power
over a distance to a 12VDC camera. If you need to use these power
adapters, allow overhead on the current rating. IE: 400ma required
for a 12V camera could use an 800ma ac to dc converter. This
would ensure the camera does not overload the converter avoiding
potential converter failure.
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- To fuse or not to Fuse
- A typical multi camera security system utilizes a mulitport
power supply, with either glass fused, or ptc (circuit breaker)
overload protection. Fuses are usually preferred, but in many
cases the PTC types allow automatic reset of the fuse once power
is removed and restored. This can eliminate the need to have
fuses laying about, and can still be cost effective. The downside
of the PTC design for cctv power is that they can take too long
to react, and may not offer adequate protection as a properly
rated fuse. Also, there are occasions where a PTC will fail permanently
resulting in the loss of a port, which may require replacement
of the entire unit If all ports are occupied). We recommend using
fuses, but if a PTC is preferred, then design your cctv power
so that you have extra ports available.
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- ICU1.com
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