Powering IP Cameras with PoE: Classification, Standards, and Advantages

IP CAMERAS WITH PoE POWER

CLASSIFICATION AND STANDARDS
EQUIPMENT
ADVANTAGES AND DISADVANTAGES

Power over Ethernet (PoE) is a technology enabling IP cameras and related devices to receive power over the same Ethernet cable (UTP category 5 or higher) used for data transmission.

This method provides a constant voltage of 48 volts with a power range of 15.4 to 25.5 watts, depending on the standard, and a current of 400 mA. Using PoE does not compromise video quality or introduce interference because:

1. Separate Power Lines: Electricity is transmitted through pairs of wires not used for data. Ethernet’s 100Base-TX standard reserves only two of the four pairs in a UTP cable for data.
2. High-Frequency Transformers: Power is isolated from the data flow using transformers, ensuring the video signal remains unaffected.

POWER SUPPLY TO IP CAMERAS

The PoE power supply connects to the RJ-45 port of an IP camera only if the camera supports PoE. If you accidentally plug a non-PoE camera into a powered port, the camera will remain safe and operational.

Power Delivery Steps:

1. Compatibility Check:
   The PoE adapter tests the device's resistance using a low test voltage (up to 10 volts). Cameras with resistance between 19-25.3 kOhms are recognized as PoE-compatible.

2. Power Classification:
   Devices are categorized into four power classes based on their energy needs. If a device exceeds allowable power limits, it is disconnected. For example:

   • Class 0: Up to 4.5 W
   • Class 1: 3.84–6.49 W
   • Class 2: 6.49–12.95 W
   • Class 3: Up to 15.4 W

3. Full Power Delivery:
   After classification, the system gradually supplies full power (48 volts). The PoE adapter monitors the current draw to prevent overloading.

PoE STANDARDS

Widely adopted standards include:

• IEEE 802.3af: Supplies 48V at up to 15.4 W, using spare wire pairs.
• IEEE 802.3at (PoE+): Supplies up to 25.5 W by leveraging all wire pairs, including those used for data transmission.

Power Transmission Methods:

• Type A: Supplies power via pairs that also carry data (phantom power).
• Type B: Uses unused wire pairs for power transmission.

Most IP cameras are compatible with either method and can accept reversed polarity without issue.

PoE EQUIPMENT

PoE devices fall into two categories:

• PSE (Power Sourcing Equipment): Devices like PoE switches or injectors supplying power.
• PD (Powered Devices): Devices like IP cameras receiving power.

For robust systems, select PoE switches based on:

1. Total port power.
2. Maximum power per port.

Most PoE switches power only a portion of their ports. If choosing an injector, prioritize models with galvanic isolation and protection against surges.

ADVANTAGES AND DISADVANTAGES

Benefits of PoE:

• Simplified Setup: One cable handles power and data, saving on materials and installation costs.
• Cost-Effective Upgrades: Existing infrastructure can be reused for PoE-enabled systems.
• Increased Safety: Eliminates reliance on external power sources, enhancing security.
• Remote Reboot Capability: Devices can be restarted remotely, avoiding physical maintenance trips.

Disadvantages:

• Higher cost compared to traditional systems.
• Increased power demands may require upgrading electrical infrastructure.

PoE is ideal for medium to small-scale indoor surveillance systems. However, outdoor setups with additional components (e.g., IR lighting, heating elements) often exceed PoE's power limits, requiring supplementary power sources