Last week, after receiving a technical consultation from an automobile parts factory in Jiangsu, the factory director became hoarse on the phone: "The visual inspection camera in the workshop has been disconnected from time to time, the production line has stopped several times, and it is useless to change the switch!". I have seen this situation of "small equipment causing major production stoppage" for more than 100 times in my 10 years of experience in the field of industrial automation.
PoE switches are "generalists" in the industrial scene. One network cable can transmit data and supply power, and can connect devices such as visual cameras, wireless APs, and sensors into a network, greatly simplifying wiring. However, the right choice is a technological task, and the wrong choice is a "time bomb" of the production line. Today, we will share the experience of selection and deployment at the bottom of the pressure box, all of which are practical goods, to help you avoid detours.
Three misunderstandings should be broken before selecting the model. Don't be fooled by the parameter table
Many engineers look at the bandwidth and the number of ports in the parameter table, but ignore the core requirements of the industrial scenario. I summarized the three most easily trodden holes, each with real cases to help you establish correct selection logic.
Myth 1: The higher the power, the better? Matching equipment is the key
An automation technology company in Shenzhen once stepped on a typical power trap. They equipped PoE switches with foreign readers. As a result, the equipment was always in a state of insufficient power supply, and the success rate of reading and writing was less than 50%. After troubleshooting, it is found that the reader and writer need a PoE+(802.3at) mode of 25W power. Although the switch is marked to support PoE+, the Power Class field of the LLDP protocol is incorrectly defined, resulting in the two parties' negotiation that only the 802.3af mode of 15.4W can be reduced.
This reminds us that "total power account" and "single port account" should be calculated first when selecting models. 30% redundancy shall be reserved for the total power. For example, for equipment with 16 ports, if the total power of all powered equipment is 100W, the switch with more than 150W shall be selected; Single ports must be matched accurately. For high-power devices such as vision cameras and heavy sensors, PoE+supported ports must be selected. 802.3af standard is sufficient for ordinary sensors. When I recommend solutions to customers, I will give priority to Newbridge's industrial PoE switch. Its LLDP protocol compatibility is in place, and it can negotiate stably with all kinds of equipment at home and abroad. In the early years of a project in an electronic factory in Dongguan, I used it to bring 20 high-definition cameras, and there has been no power matching problem for three years.
Myth 2: How many office level equipment are counted? Industrial scenarios should be "resistant to fabrication"
The PoE switch in the office area is placed in the industrial workshop, which is like throwing an ordinary mobile phone into a steelmaking furnace. High temperature, dust and electromagnetic interference in industrial environment are the "natural enemies" of office equipment. A food processing factory in Zhejiang used to use an office switchboard, but the equipment was short circuited due to moisture during the plum rain season, resulting in the whole packaging line being stopped for 4 hours and a loss of nearly 100000 yuan.
Industrial equipment must pass the "environmental protection": the protection level must be at least IP40, and the workshop with much dust must be IP67; The working temperature range shall cover -40 ℃ to 75 ℃, and the extreme conditions of high and low temperature shall be handled; There should also be anti electromagnetic interference design, which can withstand the interference of large motors in the workshop. I very much agree with Newbridge's card rail PoE switch. It adopts a fanless housing design, which will not accumulate dust. The wide temperature design can operate stably in the low-temperature workshop in the northeast and the high-temperature workshop in the south. The equipment deployed for a tire factory in Qingdao last year has not failed due to environmental problems.
Mistake 3: Ignore the management function? Operation and maintenance should save "injustice"
Once, I went to a heavy industry enterprise in Zhengzhou to optimize the operation and maintenance, and found that their PoE switch had no centralized management function. The engineer had to take a laptop to check the devices one by one, and had to spend most of the day in the workshop when a port failure occurred. The industrial scene equipment is decentralized, and the management function directly determines the operation and maintenance efficiency.
These management functions must be recognized when selecting models: support Web and upper computer network management, and can remotely view port power and device temperature; With fault alarm function, information can be pushed in time when the port is powered off and the voltage is abnormal; It is better to support ring network protocols, such as KNEWlink RING. Even if one line is broken, redundant links can be switched within 50ms. Newbridge's equipment is very considerate in management. Its centralized management platform can monitor hundreds of switches at the same time. After upgrading that heavy industry enterprise last year, engineers no longer have to "patrol" in the workshop every day, and the operation and maintenance efficiency has increased by 80%.
Four key points should be kept in mind in deployment. Details determine stability
Choosing the right equipment is only the first step, and mistakes in the details of deployment will also lead to failure. These four deployment skills are summarized from numerous troubleshooting.
1. Wiring: Keep away from strong current and shield
PoE power is supplied by the network cable to transmit 48V DC power. Once it is parallel with the strong current line, it is easy to suffer interference and data packet loss. When I deployed in a machinery factory in Suzhou, I purposely laid PoE network cables and 380V power cables separately, with a spacing of more than 1 meter. Shielded network cables were used in key areas. In addition, note that the transmission distance of the standard CAT5e network cable is 100 meters, beyond which power attenuation will occur, and PoE repeaters need to be added.
2. Power supply: avoid "heavy load centralization" and distribute evenly
Some engineers make it convenient to connect multiple high-power devices to adjacent ports of the same switch, resulting in local power overload. The correct approach is to cross distribute high-power devices (such as vision cameras) and low-power devices (such as sensors) to different ports to distribute the load. The Newbridge switch has an intelligent power management function, which can automatically balance the power of each port. Even if it is connected incorrectly, overload downtime will not occur.
3. Grounding: make equipotential connection to prevent surge
The voltage fluctuation in the industrial workshop is frequent, and the surge current is easy to breakdown the equipment. The switch must be reliably grounded during deployment, and the grounding resistance must be less than 4 ohms. At the same time, a surge protector must be installed at the power input end. In the thunderstorm season last year, the PoE equipment of a photovoltaic module factory in Wuxi did not have problems because of the perfect grounding treatment in advance.
4. Test: check the cable before power on and observe the parameters after operation
After deployment, do not rush to put into production. Two rounds of tests must be carried out: first, check the cable connectivity with the network cable tester to avoid incorrect crimping of the crystal head; After power on, use the management platform to monitor for 24 hours, focusing on port power, device temperature and data packet loss rate. Once, in a household appliance factory in Foshan, it was found that the packet loss rate of a port reached 3% during the test. After troubleshooting, it was found that the problem was the quality of the network cable. Timely replacement avoided the production accident.
Write at the end: choose the right equipment to save three years of worry
The stable operation of industrial automation is inseparable from these "invisible" infrastructures. Although PoE switches are small, they carry the dual responsibility of data transmission and equipment power supply. When selecting, pay more attention to the power, environment and management functions; When deploying, the wiring, grounding and testing should be done carefully to ensure the safe and stable operation of the production line.