Hirose: Connecting the future
Industrial Ethernet Book Issue 101 / 10
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Use of PoE splitters in new and existing systems

Power-over-Ethernet supports the process of readily integrating data from a variety of processes into both new and existing networks. Use of PoE reduces the wiring required, and the ability to switch stations on and off via a centrally managed system is beneficial to users and creates an effective networking solution.

IN AN INCREASINGLY CONNECTED WORLD, having constant access to data from all processes is really important. The Power-over-Ethernet technique supports the process of readily integrating this data into existing networks. With new splitter technology from Phoenix Contact, for example, remote, non-PoE capable controllers and I/O stations can be networked efficiently.

Power-over-Ethernet (PoE) has established itself in industrial applications as a vendor-neutral IEEE standard over the past ten years. One example of use is WiFi-based factory lighting, which often requires a large number of access points (AP) that must be installed in locations well suited for wireless communication. Suitable installation sites are usually to be found near the factory roof or even outside the building, meaning they are difficult to reach. Installing the access points is therefore expensive and takes a lot of time.

This results from the difficulty in reaching the installation sites and the large distances to be covered. Likewise, optimal positions for wireless coverage prove to be thermally challenging. This is because installation boxes installed under the factory roof are often subject to high temperatures in summer. If the devices have been installed outdoors or in refrigerated warehouses, low temperatures also come into play in winter or when the cooling system is running.

For connection to the network, each installation box requires a cable for data transmission and voltage supply including a suitable power supply unit. The use of PoE technology reduces the amount of wiring required, since only the data cable used for communication and to supply power to the components installed in the box has to be laid. The fact that the stations can be switched on and off via a managed PoE system centrally as well as based on requirements is beneficial to users. Energy is saved in applications which are only used occasionally or at particular times.

Converting voltage to 24 V DC

In order to achieve the maximum benefit from the joint transmission of data and power via PoE technology, new as well as current systems should be designed to meet the IEEE standard. If existing applications are modified or upgraded, Power-over-Ethernet can also play to its strengths. However, designers and installation technicians are generally confronted with the challenge that existing end devices - such as controllers, sensors, I/O stations for recording measurements or control and monitoring devices - which are typically not compatible with PoE must be integrated easily with as little work as possible into the new infrastructure.

Such systems are found more common that you might think. In large-scale applications, remote operator panels or HMI devices are frequently installed at locations which are ideal for users not in the vicinity of the control cabinet. In this case, the compact PoE cabling represents a significant plus. However, the difficulty here lies with the existing end devices which are not PoE compatible and installed in the remote control boxes. The voltage must be isolated from the data in order to ensure that the available components can be supplied via Power-over-Ethernet. For this purpose, the PoE voltage must be converted from 48 V DC or 54 V DC, depending on the PoE feed, to 24 V DC, which is well suited for automation.

Design optimized for tight spaces

Phoenix Contact developed the FL PD 1001T GT POV splitter that enables non-PoE compatible end participants to be readily integrated into the network. The infrastructure component is designed in such a way that it can be optimally installed in standard control boxes. Because these are often installed at locations which are difficult to reach, such as under the factory roof or outside, the splitter must be able to operate under the conditions found there. As such, the FL PD 1001T GT covers a wide temperature range, from -40° to +70°C.

Furthermore, the design of the splitter is optimized for installation in tight spaces. The component can be connected at the top and the bottom. This means that it takes up little space on the DIN rail and can be installed and cabled even in flat control boxes with ease. The power supply and data cables for the end device are guided from below out of the PoE splitter, resulting in short distances to the device. Due to potential differences, equalizing currents from the shielding occur in distributed systems.

In order to ensure reliable operation of the components at various voltage potentials, the FL PD 1001T GT internal electrical isolation both for the power supply and data cable. Without this, it could generally be assumed that potential differences and the resulting equalizing currents would cause severe damage.

A POV splitter enables non-PoE compatible end participants to be integrated into the network.

Supports all relevant standards

In order for the PoE splitter to reliably supply the end devices with power, its power supply unit provides output powers of 12.9 W and 25.4 W, depending on the PoE source. This means, for example, that a controller with multiple I/O points can be easily supplied. This also applies for redundant WiFi access points. To achieve high operational reliability, the voltage output is short-circuit proof. This means that, in the case of end devices with high starting current, there is no risk of a negative impact on the device supplying PoE which can reliably starts the appliances.

The new PoE splitter from Phoenix Contact fully supports the two relevant standards - IEEE 802.3af for Power-over-Ethernet with a maximum power of 15.4 W and IEEE 802.3at for PoE+ with a maximum power of 34.2 W - which is why the infrastructure components can be used in various applications. The splitter also allows for the supply of different wire pairs according to variant A (conductor 1/2, 3/6) or variant B (conductor 6/5, 7/8).

This means that uninterrupted operation is possible both at endspan (PoE switches) and midspan power devices (PoE injectors). For the connected end devices to be able to provide maximum power, the PoE splitter always draws on the maximum possible power for the power device and reserves it in its PSE system (Power Source Equipment).

Transmission up to 1 Gbps

Communication in industrial environments is dependent on maximum compatibility. In this context, the splitter can be used with any protocol and therefore does not alter or filter any transmitted data packets. It runs at data rates of 10 Mbps (half-duplex mode) up to 1 Gbps. Even when using the PoE splitter, the maximum range of a copper-based Ethernet transmission remains at max. 100 m between two end devices.

The FL PD 1001T GT is a PoE splitter that can be used everywhere. It enables remote stations to be easily integrated into existing networks with much less installation work required. Due to the robust design, installation is not a problem, even in difficult environmental conditions.

No configuration necessary

Using a PoE splitter, power and data which have been compiled according to the international standard IEEE 802.3af (PoE) or IEEE 802.3at (PoE+), can be isolated again at the station to be supplied. Without the need to make changes to the configuration settings, the device requests the maximum possible power from the participant supplying the power. The incoming voltage is then converted to 24 V DC, which is required for the application, in the POV splitter. Depending on the type of PoE supplying power, either 12.9 W or 25.4 W is available at the output that is short-circuit proof.

Using a PoE splitter, power and data which have been compiled according to the international standard IEEE 802.3af (PoE) or IEEE 802.3at (PoE+), can be isolated again at the station to be supplied.

The PoE splitter can support transmission rates of up to 1000 Mbps. In this process, it does not actively interfere with communication, which means that the two end devices can broker the data rate among themselves. End devices without a PoE interface, such as I/O stations or compact controllers, can easily be powered via the splitter and integrated into the network at same time.

Alexander Siegert, Product Marketing Network Technology, Phoenix Contact Electronics GmbH.

Source: Industrial Ethernet Book Issue 101 / 10
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