In electroplating, there are many interesting ways to use radio technology sensibly and effectively. By using radio systems, it is now possible to connect wear components and devices that are difficult to access to the control technology in a cost-effective way, thus providing quick and maintenance-friendly access to as many system components as possible.
This includes not only the avoidance of drag chains on the carriages and cross transfer units, but also options such as controlling the drum rotation directly on the drum units or temperature detection in the baths.
The following advantages result from the use of radio technology:
- Replacement of trailing cables
- Reduced wear
- Maintenance-free
- Lower costs
- Increased flexibilityIncreased flexibility
- Easy access to appropriate devices
Robust, wireless networks are required in order to be able to use radio technology in the environment of electroplating systems. But what role does wireless technology already play today? How important is its availability? What solutions are available?
There are currently two different wireless technologies for industrial use:
- Wireless LAN (WLAN)Wireless LAN (WLAN)
- Bluetooth
Bluetooth is used where there are smaller amounts of data to be transmitted, i.e. for measuring sensors or the control of actuators. The use of WLAN, on the other hand, is interesting where larger amounts of data or higher speeds are required. For this reason, these two wireless technologies complement each other.
We take a closer look at these two methods here.
WLAN
The development of wireless LAN (WLAN for short) has made significant progress in recent years, particularly in terms of data transfer rates and transmission stability. New end devices and applications create added value for production and its processes. WLAN is therefore playing an increasingly important role as a connection technology in the Industry 4.0 environment and especially in electroplating technology. Compared to fixed cabling, it provides significantly more flexibility in data transmission between system components. Employees benefit from quick and easy access to devices, applications and data. This not only brings advantages in terms of mobility, but also high cost efficiency when switching to new procedures and processes.
Due to its proximity to Ethernet-based protocols, WLAN is very well suited for connection to control technology using Profinet (bus system for control technology). This makes it very easy to integrate industrial WLAN (IWLAN for short) components into the control technology. The encryption of this technology ensures a high level of security against external attacks.
Furthermore, safety-relevant components such as emergency stop, personal protection or safety areas can now also be implemented with the aid of wireless technology.
One standard for two worlds
When using the IEEE 802.11 standard for WLAN in the industrial sector, different requirements need to be met compared to deployment in office environments. For example, in the case of office WLAN as a service for mobile users, the focus is on comprehensive provision, high performance, support for many subscribers, security and simple administration.
For IWLAN as part of a control structure, on the other hand, production-related, selective provision, reliability, robustness and simple and fast recoverability are crucial. In addition, the use of WLAN in an industrial environment is not as simple as in office environments. This is because the environmental conditions - for example in production halls with large areas, lots of metal and other interference factors for radio transmission - place high demands on the IWLAN infrastructures. At the same time, the components have to function in demanding environments with extreme heat, cold, dust or moisture. As robustness and stability must be guaranteed, the housings are impact-resistant and sometimes use different connections.
For this reason, industrial WLAN components must meet the following requirements:
- Coexistence with other wireless components
- Long range
- High security
- Robustness
- Short response times and corresponding time behavior
- Connection monitoring and diagnostics
The sharp increase in the number of users communicating via WLAN poses a major challenge, as does the volume of data transmitted and the amount of data generated per user. The massive growth in data volumes is problematic, as all content has to be managed via a shared medium and uses up the available bandwidth in equal measure. In addition, other wireless methods are sometimes also used in the same radio ranges, for example applications that use Bluetooth or building surveillance systems (video & access systems). Multiple occupied channels and overlapping frequency usage lead to critical interference, especially in industrial environments.
This is precisely where high reliability and availability requirements must be met. In particular, this includes an uninterrupted connection when roaming, i.e. switching from one access point to another, as well as a guarantee of data reception at a specified arrival time. A conventional WLAN is not capable of this. Accordingly, manufacturers such as Siemens have developed their own functions based on the IEEE 802.11 standard. These include iPCF (industrial Point Coordination Function), iHOP (industrial Frequency Hopping) and RCoax cables.
Special solutions for IWLAN
- iPCF extends WLAN with a deterministic process that allocates transmit and receive time to subscribers in a coordinated manner. This allows other subscribers to be treated with a lower priority in order to comply with critical response times and specified reception times. This also speeds up the roaming process so that the communication link is not interrupted even during the transition between different access points.
- iHOP ensures that the IWLAN jumps to different channels one after the other. The process is coordinated by the access point, which synchronizes with its IWLAN clients. Hopping works so quickly that data transmission is generally not affected, even if one channel is disrupted. The access point closes this immediately and temporarily removes it from its hopping sequence. If, for example, the frequently used 2.4 GHz band is no longer available, the 5 GHz band can be used to ensure availability.
- RCoax cables are specially manufactured coaxial cables that enable a reliable wireless connection even when conventional antenna technology can only be installed with great effort. Ultimately, this is a WLAN with a cable instead of an access point. This leaky waveguide technology is used in tunnels, ducts or elevator shafts, for example, but also for communication with rail-guided vehicles.
When using WLAN in an industrial environment, it must be taken into account that there are other wireless infrastructures as well as established and emerging radio-based technologies such as Bluetooth Low Energy, etc. For this reason, a frequency management system must be established in a company with precise documentation of the frequencies and channels used. This ensures interference immunity and reliability of the corresponding networks.
WLAN: 2.4 GHz or 5 GHz
Wireless networks are now everywhere. Whether UHF, VHF, GSM, UMTS, LTE, Bluetooth or WLAN, wireless data communication is ubiquitous. WLAN in the 2.4 and 5 GHz band is probably the most widespread and most used wireless network. We use it every day with our computers, smartphones and tablets, whether at home, at work or in a restaurant.
A Wi-Fi network can use two frequency bands to send and receive data, one is the 2.4 GHz band and the other is the 5 GHz band. The frequency bands for WLAN are significantly higher than most other frequency bands, e.g. for television, radio, GPRS, UMTS and LTE. The bands for WLAN are also significantly wider. This means that more data can be transported. As with a highway, significantly more cars can drive on a four-lane road than on a single-lane road. All WLAN networks use the IEEE 802.11 standard. Most WLAN routers and access points can operate on the 2.4 GHz IEEE 802.11b and IEEE 802.11g standards as well as on the 5 GHz IEEE 802.11a standard. The transmission rate is the same for both frequency ranges. The WLAN standard IEEE 802.11n supports both frequency bands. The WLAN standards IEEE 802.11ac and IEEE 802.11ax only support the 5 GHz band.
2.4 GHz range
The 2.4 GHz is used a lot and is therefore overcrowded. This is due to the fact that the 2.4 GHz band only provides three overlap-free 20 MHz channels (see table on next page). The WLAN standard IEEE 802.11n even supports 40 MHz bandwidth for 2.4 GHz WLAN. This means that only one overlap-free channel is possible. So if two or more parties in a house or block of flats use 2.4 GHz WLAN with the current IEEE 802.11n standard, there will definitely be congestion in the data network. There are also other technologies competing with WLAN in the 2.4 GHz band. These include Bluetooth, cordless telephones (DECT), microwaves, etc. With WLAN, the competition on the data highway leads to significant packet loss, loss of speed and complete interruptions. With radio remote controls, radio interruptions can cause machines, cranes and systems to go into emergency stop mode. In the IEEE 802.11n standard, the 2.4 GHz part is also called IEEE 802.11bn or IEEE 802.11gn.
5 GHz range
The 5 GHz WLAN band looks quite different. With 23 non-overlapping channels, compared to the 2.4 GHz band with three, a much wider highway is available here. In addition, significantly fewer devices and technologies use the 5 GHz band. Nevertheless, more and more WLAN routers and access points now support the 5 GHz band, either as an alternative to the 2.4 GHz band or even both bands simultaneously. More and more end devices such as laptops, smartphones and tablets now also support 2.4 and 5 GHz WLAN simultaneously.
Many companies, especially in the industrial sector, are switching to the 5 GHz WLAN band to avoid radio dropouts and interference in data communication. Often the expectations and the promise of no interference with radio traffic have not been fulfilled. But there is also interference in the 5 GHz band. In the 5 GHz band, for example, there is radar such as weather radar and digital satellite communication, which have priority over WLAN.
The permitted transmission power for WLAN in the 5 GHz band (200 mW) is significantly higher than in the 2.4 GHz band (100 mW). The 5 GHz WLAN range is significantly higher than in the 2.4 GHz band, especially for directional radio links in outdoor areas. This brings advantages in 5 GHz WLAN. In indoor areas, 2.4 GHz WLAN penetrates walls and ceilings better due to the lower frequency. This is why the range of 2.4 GHz WLAN is better indoors in most cases.
| Channel | Carrier frequency | Frequency range | Europe | USA | Japan |
| 1 | 2412 MHz | 2399.5 MHz-2424.5 MHz | X | X | X |
| 2 | 2417 MHz | 2404.5 MHz-2429.5 MHz | X | X | X |
| 3 | 2422 MHz | 2409.5 MHz-2434.5 MHz | X | X | X |
| 4 | 2427 MHz | 2414.5 MHz-2439.5 MHz | X | X | X |
| 5 | 2432 MHz | 2419.5 MHz-2444.5 MHz | X | X | X |
| 6 | 2437 MHz | 2424.5 MHz-2449.5 MHz | X | X | X |
| 7 | 2442 MHz | 2429.5 MHz-2454.5 MHz | X | X | X |
| 8 | 2447 MHz | 2434.5 MHz-2459.5 MHz | X | X | X |
| 9 | 2452 MHz | 2439.5 MHz-2464.5 MHz | X | X | X |
| 10 | 2457 MHz | 2444.5 MHz-2469.5 MHz | X | X | X |
| 11 | 2462 MHz | 2449.5 MHz-2474.5 MHz | X | X | X |
| 12 | 2467 MHz | 2454.5 MHz-2479.5 MHz | X | X | |
| 13 | 2472 MHz | 2459.5 MHz-2484.5 MHz | X | X | |
| 14 | 2484 MHz | × (11b) |
Tab. 1: Frequency overview (1)
WLAN optimization
An important aspect when using wireless technology is wireless network optimization. It is important to plan the components so that they are designed for the existing conditions and installed accordingly. This is of course also a matter of experience, but can be planned accordingly with the help of tools.
The following points must therefore be taken into account when designing the WLAN network:
- Correct component design and planning
- Correct frequency selection
- Correct channel selection
- Check the attenuation range
- Select the appropriate antenna
Bluetooth
Due to the adaptive frequency hopping (AFH) method used, Bluetooth offers a very reliable and interference-resistant radio connection. This advantage of Bluetooth over other radio technologies (including WLAN) was recognized early on by various manufacturers of automation products. As a result, Bluetooth-based industrial products were developed that are used in various areas of industry to communicate wirelessly between different components in machines. Bluetooth can now also transmit data from fieldbuses (e.g. Profinet), making it very easy to integrate this wireless technology into control systems.
| Channel | Carrier frequency | IEEE 802.11a (USA) | IEEE 802.11h (EU) | EEE 802.11j (Japan) |
| 36 | 5.180 GHz | Yes | Yes | yes |
| 40 | 5.200 GHz | yes | yes | yes |
| 44 | 5.220 GHz | yes | yes | yes |
| 48 | 5.240 GHz | yes | yes | yes |
| 52 | 5.260 GHz | yes | yes | no |
| 56 | 5.280 GHz | yes | yes | no |
| 60 | 5.300 GHz | yes | yes | no |
| 64 | 5.320 GHz | yes | yes | no |
| 100 | 5.500 GHz | no | yes | no |
| 104 | 5.520 GHz | no | yes | no |
| 108 | 5.540 GHz | no | yes | no |
| 112 | 5.560 GHz | no | yes | no |
| 116 | 5.580 GHz | no | yes | no |
| 120 | 5,600 GHz | no | yes | no |
| 124 | 5.620 GHz | no | yes | no |
| 128 | 5,600 GHz | no | yes | no |
| 132 | 5.660 GHz | no | yes | no |
| 136 | 5.680 GHz | no | yes | no |
| 140 | 5.700 GHz | no | yes | no |
| 147 | 5.735 GHz | yes | no | no |
| 151 | 5.755 GHz | yes | no | no |
| 155 | 5.775 GHz | yes | no | no |
| 167 | 5.835 GHz | yes | no | no |
Tab. 2: Frequency overview (2)
Properties of Bluetooth
- Transmits in the ISM band (Industrial, Scientific and Medical Band frequency range between 2.402-2.480 GHz)
- Available worldwide
- However, interference can be caused by WLAN, DECT telephones or microwave ovens operating in the same frequency band, for exampleInterference can be caused by WLAN, DECT telephones or microwave ovens operating in the same frequency band, for exampleFrequency hopping to achieve robustness against interference
- Range of up to over 100 m possible
- Data transmission rates of up to 2.1 Mbit/sec. possible, depending on the version
- Protection against eavesdropping and intrusion only given for PINs with more than 8 characters. Bluetooth is considered secure here.
- Although Bluetooth transmits in the same frequency band as WLAN, Bluetooth has different interface specifications (a different protocol applies for data exchange)
- As the transmission power is relatively low, battery-operated sensor actuators can also be equipped with Bluetooth. For example, battery-powered environmental sensors can be installed in locations that are difficult to reach with network or fieldbus cables.
Conclusion
Thanks to years of experience in the field of industrial data transmission and a correspondingly large number of installations in the field of electroplating systems, we can only speak positively in favor of the use of wireless technology. The installation of systems is much simpler and can be prepared accordingly. This considerably reduces installation times. In addition, several years of operation have shown that there are hardly any failures in the area of radio technology and that this technology proves to be very stable.
