IVC’s Tech Support Manager Explains Power over Ethernet

We sat down with IVC’s tech support manager, Rafael Bastidas, to get his take on the use of PoE technology for IP video cameras.

Interviewer: Hi Rafael. Let’s start at the top. What is PoE and why has it become the preferred way to power IP cameras?

Rafael: PoE stands for Power over Ethernet. This technology combines both power and data transmission into a single Ethernet cable, significantly simplifying the camera installation process. So, instead of needing two separate cables to connect your IP camera, you just need one. The typical maximum distance for PoE is around 100 meters, or 328 feet. There are two ways that power can be provided- either through a POE switch that provides both network connectivity and power, or through an injector that transforms 110VAC and sends it out over the Ethernet cable as DC.

Interviewer: Are there different types of PoE?

Rafael: Yes, there are two types: Active and Passive. The main distinction lies in how they deliver power.

Active PoE involves a negotiation phase where the client device and the PoE source communicate to determine the power requirements. This negotiation ensures that the right amount of power is supplied, which helps prevent any damage to the equipment. To ensure interoperability between devices and injectors, Active PoE adheres to the industry standards 802af, 802at, and 8023bt. These standards enable devices and injectors to negotiate and provide the required power efficiently.

On the other hand, Passive PoE supplies power continuously without negotiation. It’s essentially “on” all the time, providing a constant power feed. However, it lacks the precise control over power delivery that Active PoE offers. There are various passive PoE standards, often categorized by voltage levels (e.g., 24V or 48V).

There are many situations when passive PoE is required because standard PoE won’t work. For example, passive PoE needs to be used when sites have DC power of 12V DC or 24V DC. Rather than using an inverter, which is not efficient, in these cases we can control the passive PoE thru special injectors that internally handle the DC to DC conversion required.

We also use high power passive PoE when designing custom cameras. This is because the final camera assembly is composed of several parts and devices that work together; however not all of them are native standard PoE. Some examples are when extra heaters or lighting are requested or we have to add LTE/WiFi connectivity to existing products.

Interviewer: What types of issues do you run into when implementing video systems with PoE cameras?

Answer: We have encountered many situations where devices do not power up in the field. This can be very frustrating, particularly after the equipment has been mounted. When this happens, the most common culprits include crimping issues, wiring issues, and device compatibility.

With crimping, if the cable ends are not properly terminated it can lead to all sorts of issues including damage to the end devices. However, having mismatched termination standards can be problematic.  Basically we like to keep all the wiring across the network terminated as T568-B to avoid crossed signals between PoE source and end devices. Some of our customers have had older wiring terminated as T568-A which has led to faults on PoE injectors or switches.

Wiring can be a problem when customers use nonstandard network cables. CAT5e and CAT6 are cabling standards that must be followed to ensure the installation uses the correct colors for TX, RX pairs, as well as the correct number of pairs. This is critical to achieve the desired speed/duplex and initial power negotiation. But in the case of passive PoE, nonstandard cabling can result in not only the equipment not working, but also the equipment getting damaged. We have encountered problematic situations where the color coding at a site completely differed from the standard CAT5e/CAT6 cabling.

We had one instance where a high-power camera was mounted on a crane and the customer wanted to use existing networking cabling. We designed the high-power camera with High Power passive PoE which requires four pairs of cable, as our PoE passive injector uses two pairs exclusively for power. The crane had a two-pair twisted network cable already installed which did not work with our high-power PTZ camera, and new CAT6 wiring was required for the system to work. When it comes to using passive PoE, we have learned to ask the right questions up front – getting all the required details related to cabling, distance, and termination.  In most cases, we supply our own passive injectors to ensure proper functionality.

Device compatibility issues occur when customers use nonstandard PoE sources such as PoE injectors or midspans. In these cases, the PoE devices do not power up or have negotiated with the wrong speed/duplex settings.  To avoid these problems, we make sure each compatible PoE source is labeled with what standard it supports and its power budget.  Having this information allows our support team to troubleshoot issues quickly.

If multiple cameras are powered from a single switch, the total power draw can exceed the switch’s power limit.  In these cases, we can add PoE injectors as the number of cameras increases. Similarly, we use PoE injectors when the switch’s rating is below the required standard for the camera, such as with a 802.3bt PTZ camera.

Interviewer: Any final comments?

Most customers are aware of PoE as a concept, but understanding the technical aspects can prevent unnecessary problems during and after installation of video systems. At IVC, we assess our customer’s specific needs and offer customized solutions that meet their exact requirements.

Interviewer: Thanks Rafael.

 

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