The use of Power over Ethernet (PoE) in industrial settings has increased rapidly in the last 10 years.
At one time, communications between devices happened over an RS232 or RS485 physical layer which provided slow, inflexible but reliable communications.
Then came PoE, a communication protocol that’s fast, can be used for almost any purpose, and is cost effective.
What is PoE?
According to Paul Savage, CEO of Nextek Power Systems, located in Detroit:
“PoE refers to the use of some number of wires that are part of a structured cable, usually Category 5 cable, for the delivery of electrical power, in addition to its original intended use as a communications carrier.
“Unlike Class 1 power levels, which must be handled by licensed electricians because of the voltages they carry can be lethal, PoE voltages are Class 2 at less than 60 volts (V), below the shock and startle hazard. Class 2 cabling doesn’t need conduit or metal cladding, so it installs faster and can be rerouted easily and safely.”
PoE is a neat, simple technology that’s use has become common in commercial and residential buildings–and now it’s moving to the factory floor. There is no longer any technical reason why Ethernet can’t power most industrial devices.
Complex devices like Human-Machine Interfaces (HMI), optical sensors, and level management devices are the most likely current applications for PoE in the industrial arena. This is due to the reduction of power demand from these devices, as well as the greater availability of PoE and equipment. PoE is capable of direct linking with most every device.
Following, is a list of the major advantages that are galvanizing a move to PoE into industrial settings:
PoE is Safe
PoE protects both users and legacy equipment from damage from the dangers of electrical power. It’s low voltage.
And even at this relatively safe voltage level, to avoid damage or accidental contact, the power source equipment (PSE) sends a 10 volt (V) test current to verify the existence of a 25 ohm resistor at the power device (PD) before the full power is applied. If the PD stops using power, power from the PSE stops, then testing resumes.
As part of the PoE standard, delivery is designed to protect network equipment from overload (over-current), under powering (under-current), or mistakes made during the installation process. System integrators set the power limitation for each port on a PoE switch, which keeps them from providing too much power.
Another feature is that administrators are able to incorporate “classification”, which assists power management, reliability, and safety. In the start-up process of a PoE connection, the PD can be set up to indicate its power class to the user. There are 5 power classes and only 3 different power-level bands that devices can fall into.
PoE is Economical
With the use of one cable for both data and power for network connections, PoE is most cost-effective–both for installation and maintenance. This cost of time and money is reduced with this type of cable installation. In addition, PoE network cables don’t require the expense of a licensed electrician.
PoE power comes from a central source rather than a collection of distributed wall adapters. It can be backed up by an uninterruptible power source or controlled and quickly disabled or reset, which makes the installation and distribution of network connections simple, fast, effective, and less costly.
PoE is Flexible
The overriding feature of PoE is flexibility:
- PoE is standards-based
- Interoperational across vendors
- Can be configured across all variations of network topologies (including ring, mesh, and other networks)
- Industrial network management tools (such as RSTP/STP, IGMP, and VLANs) are available on high-quality industrial switches
- Single-cable power and data delivery (typical in fieldbus networks) is available
- Factory floor configuration changes can be made simply and quickly
- Designed to operate over standard network cable (such as Cat 5).
- Uses conventional RJ45 connectors
- Not bound to an electrical outlet, devices (such as IP cameras and wireless access points) can be located almost anywhere
- If the end device isn’t designed for PoE, a PoE splitter can provide separate outlets for power and data
PoE is Reliable
PoE provides power source redundancy. It has the ability to configure Ethernet for redundant data configurations. Combining multiple networks is complex and often requires a lot of equipment, programming, and maintenance.
With the use of PoE, you get a simple interface that manages many networks in diverse locations via graphic interface.
PoE has Power (PoE+)
The 802.3af PoE standard is the perfect solution for network devices that need no more than 15.4 watts of power. However, many devices need more power than that.
To answer this need, the 802.3at standard (PoE+) was introduced by the Institute of Electrical and Electronics Engineers (IEEE). With the added power that PoE+ brings to the table, you can connect devices such as pan-tilt-zoom (PTZ) security cameras, thin client, video phones and WiMax transmitters.
PoE+ has the following features:
- Increased Electrical Power: PoE+ doubles the original standard amount of electrical power to 30 watts.
- Compatible with 802.3af PoE: All PoE+ switches and injectors are compatible with all standard PoE devices.
- Smart Power Budgeting: With PoE, both power sources and powered devices communicate to balance the availability of electrical power.
- The PoE+ (802.3at) standard works alongside the PoE (802.3af) standard. It doesn’t replace it.
PoE has Industrial Applications
There are many reasons to use PoE in an industrial environment. PoE is best when large data transfers and flexible distribution of power is needed. Here are some of the more significant industrial applications that PoE can handle:
- Security: PoE is ideal for any automated security system. IP surveillance cameras require huge amounts of bandwidth. PoE has a scalable backbone technology, as well as the ability to provide power and control gate entry systems.
- RFID/infrared: Devices like radio frequency identification (RFID) and infrared bar code readers track components, assemblies, and people–and have many industrial uses (such as, inventory control, material flow, and security). Simply put: PoE makes it easier, faster, and less expensive to place readers in more places.
- Interconnectivity/Accessibility: As PoE extends Ethernet to the factory floor–the best of both serial/bus and TCP/IP world come together. Power backup devices (such as I/O and PLCs) already have Ethernet links, but their power needs are just too high for a strictly PoE solution. However, PoE power of control and communication modules can help with backup, continuity, and orderly shutdown should the primary power fail.
Here are some other applications/devices available at this time:
- Smart signs/web signs
- Rugged VOIP
- Lighting controllers
- Audio and video systems
- Retail and shipping point of information systems
- EPOS systems
- Building access control systems
- Time and attendance systems
- Building automation
- Battery chargers for phones, PDAs, etc.
- Laptop and PDA access points
A Last Word on PoE
Because of PoE’s inherent stability, reliability, and safety, it’s a favored candidate for full scale use in industrial settings. Today, this technology has the potential to take over entire buildings in the commercial world. Its use in the industrial arena is just as bright for the future.