Securing Power on the Network
Behind every properly designed security system lurks a low-voltage power supply. Selecting the right device ensures proper and reliable functioning. Know what factors to consider – particularly where it comes to networked-based solutions incorporating power over Ethernet (PoE).
Network technology is becoming increasingly prevalent in the security space. In the past few years alone weve seen advanced systems configurations evolve that range from hybrid networked camera multiplexers to integrated IP-based surveillance, access control, intercom and security systems. ©iStockphoto.com/ryasick
[IMAGE]12174[/IMAGE]Powering Up PoE Devices
People often under estimate the power consumption totals for powering up PoE security devices. To show how quickly the power consumption can add up, let’s review a typical scenario.
Consider a system with a total of 10 IP cameras and six access control devices. Of the 10 IP cameras, six are placed indoors and four are housed in outdoor enclosures. A typical indoor fixed IP camera has a maximum current draw of 6.49 watts. A PoE outdoor camera enclosure that provides power for the heater/blower and passes power for the camera has a maximum current draw of 25.5 watts. The access control devices in our example system have a maximum current draw of 12.95 watts each. (These values have been verified by testing products from various manufacturers)
Together the video surveillance and access control devices require a total of 192.74 watts for operation. We also have four devices that comply to the PoE+ IEEE802.3at standard of 25.5 watts. Seeking a PoE switch that will achieve the power consumption and the PoE+ standard can alone be a time consuming process. On this installation, of course, we are also including access control.
Many local jurisdictions require products that must adhere to the UL294 Listing for access control. Finding a PoE switch with the UL294 Listing will take even more time. With the stringent power requirements and standards, it makes more sense to deploy a managed midspan that meets these specifications and system requirements.
Following is a basic parts list (not including cabling, door hardware and various materials):
- Head end (recording and access management server)
- Basic or managed switch
- Managed midspan
- Devices (10 fixed PoE IP cameras)
- 4 PoE Housings with heater/blower
- 6 PoE access control controllers/readers
Note: This application did not take into account an installation that had PoE IP p/t/z cameras, PoE IP-based IR cameras or PoE illuminators. With these devices, the power consumption would be substantially higher.
How Devices Meet Network Needs
Many IP cameras now have the ability to record images to optional SD cards in the event of a loss of network connection. Imagine losing the network connection on a PoE switch and/or needing to reboot the switch after a software update. Once power is interrupted, even cameras with onboard SD will not operate.
With a PoE midspan this potential shortcoming does not exist. The PoE midspan is simply passing data from a standard or managed switch and injecting the PoE. If your cameras have an SD card option, the cameras are still recording even with a loss of network connectivity. This is an important feature to consider since it helps ensure that cameras remain active in some capacity.
Today’s IP video surveillance cameras are basically tiny computers processing large amounts of data. Just like your PC, there is always the possibility that a camera will lock up. Traditionally, the end user would call the integrator to schedule a service call. A responding service tech needs to be dispatched to simply power down a camera to reset it. This is both an expensive and time-consuming exercise.
Using an extremely reliable managed PoE midspan on the network, you have the ability to perform the camera “reboot” from anywh
ere you have Internet access. To reset the power on any or all ports, simply logon.
From the same managed PoE midspan you should also have the ability to allocate power to devices based on their specific type and requirements, see how much current the device is using, and evaluate the total power consumption of all your devices. Other features of a good managed PoE midspan should include:
- PoE shutdown with a contact closure, the ability to turn specific ports off when not in use
- The capability to recognize non-POE devices via a simple trigger input
- Over-current protection for each port with automatic reset
- Local or remote monitoring of port status
By using a standard or managed IP switch with a PoE midspan, it is much easier to manage system functionality.
Other advantages of this configuration include system scalability and flexibility (i.e. cascading for longer distances) and the ability to easily match to the power requirements of the edge device.
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