In the field of security monitoring, many network devices currently in use support PoE power supply. In the network monitoring construction, in order to reduce wiring costs and make it more convenient and faster, most engineering companies will consider using PoE power supply, that is, using PoE switches to power surveillance cameras. So, how many devices can a PoE industrial switch supply power?

1. PoE switch power supply standard

To see how many cameras can be powered by a PoE switch at the same time, two aspects must be considered: the power supply standard of the PoE switch and the total power supply of the PoE switch. The power supply of the PoE switch can be understood as the single-port power supply of the PoE switch. There are two standards for PoE switches that are popular on the market, IEEE802.3af and IEEE802.3at.  The IEEE802.3af standard defines a power supply of 15.4W, and the IEEE802.3at standard defines a power supply of up to 30W. Due to different power supply standards, the single-port power supply is also different. For example, the camera power is 9W, and the af standard PoE switch can be used;  If the camera power is 20W, you need to use an af standard PoE switch; if the camera power is more than 30W, you need to use a dedicated PoE power supply module to supply power. 

Generally speaking, a PoE switch that supports both af and at power supply standards has self-adaptive power supply. For example, if it is connected to a 5W device, it provides 5W of power; if it is connected to a 20W device, then it provides 20W of power.

2. The total power of industrial PoE switches

The total power of a industrial  PoE switch is a very important indicator, directly related to how many cameras can be brought. Taking a 24-port PoE switch with a power supply of 400W, the total power of the PoE switch is about 370W after removing the loss. 

Under the IEEE802.3af standard, it can supply 24 ports (370/15.4=24), that is, it can supply power to 24 cameras at the same time, that is, full power supply. But if it is calculated according to the IEEE802.3at standard for a single-port maximum power supply of 30W, at the same time, it can only supply power to 12 ports at most (370/30=12).

In actual use, the maximum power consumption of many common webcams is low, basically not exceeding 15W. If each PoE port reserves power according to the maximum power (for example, 30W) at this time, some ports will use PoE power. Endless, but some ports can’t distribute power. For example, some PoE switches support dynamic power allocation, which can avoid this situation. When purchasing a PoE switch, it depends on whether the switch supports dynamic power allocation, so that each port only allocates the power actually used, so that the power supply of the PoE switch can be used more efficiently.

3. Sharing experience of using PoE industrial switches

a. The use of switches that support dynamic power distribution can maximize the power supply efficiency;
b. First understand the maximum power consumption of the powered device, and then divide the total power supply of the PoE switch by the maximum power consumption to get how many devices a PoE switch can supply.