I Have The Power - CCTV Power Needs
By Christian M Gillman
When building your surveillance system you will need to select a CCTV power supply. This can be a little more involved then simply plugging an adapter into the wall. Let's address a few of the features and differences amongst CCTV power supplies.
Single Port Vs. Multiple Port
The name says it all. Are you going to use a single port power adapter at each security camera; or are you going to have a single power box to supply power to all of your cameras? If your surveillance system only has a couple of security cameras; then it may be a good idea to just use a single power adapter at each camera. In fact even four camera adapters all running to a power strip may not be a big deal.
Neatness and a clean installation can be quite an attractive option however, and it may be a more ideal situation to have a single power box supplying power to your entire system; especially if you have a large number of cameras. The choice for this is really dependent on the user and their power requirements and aesthetic preferences.
DC vs AC Power Supplies
Security camera power supplies for the majority of time have been 24VAC. Throughout the past 10 years the advent of smaller more compact and covert cameras has led to an increased number of 12VDC options. Both of these are lightly regulated (low voltage) for construction which allows flexibility in surveillance installations.
12VDC uses a smaller footprint for security cameras because it does not need a rectifier. Although this type of power supply was originally designed for covert surveillance applications, it has become quite popular for larger C/CS mount type security cameras. On the downside 12VDC is not a good solution for long cable runs and in fact the 12VDC power boxes can cost more than their 24VAC counterparts.
These power supplies are often simple transformers distributed through multiple ports or used in a single application. The advantage to these power supplies is found in the cost of multiple port units, as they have a reduced amount of components needed. Another advantage is their ability to keep a solid power signal over longer CCTV cable runs.
Mixed Surveillance Systems
Through the use of power converters many surveillance systems will use a mixed assortment of power supplies both 12VDC and 24VAC. These converters allow 24VAC voltage to be regulated down to 12VDC. If a converter is going to be used in a system you want to make sure to allow for overhead on the current rating. For example if you use a 12VDC 400ma power supply; then you are going to want to use a 800ma AC to DC converter. This will help avoid potential conversion failures.
Should You Fuse
Most multi camera surveillance systems use a multiport power supply with either a glass fused or PTC (circuit breaker) overload protection.
For most applications fuses are preferred, but in many situations the use of the PTC type allows for an automatic reset of the fuses once the power is removed and then restored. The downside to this system is that the PTC system can take too long to react and it may not offer the proper power protection that you would get from a properly rated fuse. In fact there are occasions where a PTC will fail completely; leaving you with a dead port.
Generally fuses are recommended, but if a PTC system is designed; it is a good idea to have extra ports on hand.
Christian M Gillman has worked in the surveillance industry for over 6 years. Subscribe to our monthly newsletter, learn more about surveillance, and find great products at http://www.cu1.com
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