Power Over Ethernet
GarrettCom offers a range of Power over Ethernet (PoE) products ranging from four and eight port modules that fit into the 6K series of industrial managed switches to the smaller and rugged PS14P PoE Switches and PES42 PoE Edge Switches.
Power over Ethernet (PoE) in a nutshell, makes use of an Ethernet cable’s four twisted pairs - where only two of the pairs are used for data, the IEEE 802.3af specification allows the remaining pairs to carry power!
This technology represents the only truly universal power standard. Whilst there are differences in the mains plugs in the UK to that of Europe and again to the USA, the RJ45 connection and –48V voltage of PoE are standard the world over!
The potential for PoE, then, is enormous, and need not be limited to the harsh environments of the industrial marketplace.
Today there are nearly 200 types of device which are PoE enabled including:
- Wireless access-points (airports, warehouses, etc.)
- VoIP phones
- Industrial devices (sensors, controllers, meters etc.)
- Access control and Help-points (intercoms, entry cards, keyless entry, etc.)
- Lighting controllers
- Remote Point of Sale (POS) kiosks
- Electric razors
- Security Cameras
Over the next few years it is likely that PoE will rise to become the power source of choice for devices such as smoke/fire detectors, RFID scanners, Audio/Video jukeboxes, vending/gaming machines and even chargers/docking stations for PDAs and mobile phones.
As trends in VoIP, Wi-Fi (802.1) wireless networks, and security accelerate, the numerous benefits provided by PoE can help turn good ideas into practical applications. These benefits include:
- Easier deployment – Access to hard-to-reach locations or places with a lack of space for power deployment, such as roadside, external walls and internal ceilings, becomes much simpler and easier to maintain.
- Lower cost – Costs can quickly escalate when the installation of separate power outlets are factored into a project. PoE switches save both time and money by avoiding the need for separate installation of Power outlets.
- Multi-location – Wherever there is an Ethernet connection, a powered device can be used.
- Increased uptime – If a UPS is used in the power supply for the PoE switch, reliability rises towards the optimum “five nines” due to reliance not being placed on the mains AC voltage supply.
- Improved Safety – 48 Volt Direct Current levels are much safer than AC mains voltage.
- Plug and Play – Equipping applications with PoE switches is simple and enables interoperability with a growing variety of devices.
The PoE standardisation project began in 1999 and in 2003 the Institute of Electrical and Electronics Engineers (IEEE) task force ratified the technology into the Ethernet standard 802.3af. The IEEE 802.3af standard – also referred to as Data Terminal Equipment (DTE) Power via Media Dependent Interface (MDI) – is the first international standard to define the transmission of Power over Ethernet infrastructure.
The mechanism for delivering power via PoE is similar the way in which the PSTN (Public Switched Telephone Network) carries enough power to every public telephone handset. PoE delivers DC power of up to a theoretical maximum of about 15W per cable. In practice, however, a maximum power of 12.95W is available, limited by degradation of power over the cable – typically standard Ethernet cabling of CAT5 or better.
A CAT5 cable has four twisted pairs, but only two of the pairs are used for data. The IEEE 802.3af specification allows either the spare pairs to be used (pins 4 and 5, or 7 and 8) or the data pairs (pins 1 and 2, or 3 and 6) to carry the power.
Typically a PoE system consists of both Power Sourcing Equipment (PSE) and a Powered Device (PD). The PSE may either be an Endspan (L2 Ethernet switch supporting PoE) or a Midspan (PoE hub). The PD is a PoE-enabled terminal such as an IP phone. PoE systems are deployed in a “star topology”, so each PD is connected to a separate channel of the central PSE.
GarrettCom has built the first hardened PoE switch specifically targeted at the industrial market. By integrating Ethernet switching, PoE power sourcing and industrial-hardened components, GarrettCom has delivered single a unit that is ready and able to support industrial strength PDs.
The arrival of PoE power sourcing Ethernet switches for industrial Ethernet applications changes the network design possibilities. The 4-port PS14P PoE Convenient Switch will save money and space, as well as increase reliability for a wide spectrum of applications.
Not only can PoE allow a whole host of network devices to be powered in remote locations where access to power is unavailable, but it opens the door to a whole new world of exciting possibilities for consumer and business electrical products. It is almost certain that PoE will herald major changes for industrial applications. Despite the available power in a PoE connected device being limited to about 13 watts, the advantages of blending signal and power in one Ethernet cable connection will contribute to the already-rapid transition to Ethernet based industrial control systems.