The New Generation of Multifunctional Lighting Controllers
Theoretically, any PC can manage the control aspect of this lighting if it is connected to a network, and mobile options are also available with control via smartphones or tablets.
This results in the demand for lighting control that is as flexible and effective as possible. Terms as Konnex (KNX), Digital Serial Interface (DSI), Digital Addressable Lighting Interface (DALI), and Digital Multiplex (DMX) appear
For lighting control, customers may consider a home bus like KNX, an open standard that is supported by over 100 European companies. However, it requires its own bus system, and extending the installation at a later date is usually seen as too time-consuming and too expensive.
DSI (Digital Serial Interface) is a protocol that was originally developed by the company Tridonic. The information is transmitted over a simple 8-bit protocol. The disadvantage of this method is that each channel needs to be hardwired to the lights. This has resulted in the emergence of the DALI interface, which is based on DSI.
DALI is one of the most cost-effective control options, as the 1200-baud control signal is transmitted via a 2-wire bus. A simple NYM 5×1.5mm² cable is sufficient to handle both power supply and signal transmission to the ECGs at the same time. It can be combined with KNX or other home buses by means of the appropriate gateways. However, DALI is limited to simple on/off and dimming functions. In addition, it only supports a maximum of 64 individual devices (i.e. addresses), 16 groups (group addresses) and 16 ambiences (ambient light values).
In order to get round these limitations, DMX is available. Originally developed for theatrical lighting, it is an open standard that has been established for several years. DMX-512 enables simultaneous control of brightness (dimming), colour changes and movement, such as for moving heads. At 250kbit/s, the baud rate is high enough to control a large number of lamps. DMX-512 can address 512 channels, known as a DMX universe.
RS-485 is the electrical standard for DMX-512. A Universal Asynchronous Receiver Transmitter (UART) protocol is used to transmit data. This is another case where adding wiring at a later date can be very time-consuming, because a maximum of 32 receivers can be connected to one DMX-512 bus. A repeater and splitters are also required. Due to the high data transfer rate, the installation required an appropriately shielded cable with 110 Ω impedance. As a result of these requirements, a pure DMX-512 system has limited suitability for architectural lighting.
An alternative would be to transmit DMX information over IP-based networks, which can be found in every modern building. Ethernet cables and WLAN for office communications are usually available on every floor – and even in every room. This makes it much easier to connect the individual lighting elements, and video applications can be included too.
This brings up the question of how to connect the control devices to the lighting elements. One solution is Art-Net, an IP-based protocol for transmitting DMX information or other user data using standard network technologies, including cost-effective wired or wireless network structures. This would theoretically enable the control of 32,786 DMX universes, giving almost limitless possibilities for future additions and extensions. The specifications were developed by the company Artistic Licence and are available for download from its website at https://www.artisticlicence.com/WebSiteMaster/User%20Guides/art-net.pdf)
Put simply, one can think of the physical layer as having Ethernet cables that replace DMX cables for parts of the data transmission path. This means that DMX transmitters are no longer necessary because the signals are being sent via an IP port. Another advantage of this method is that is features bidirectional communication for checkback signals.
In theory, Art-Net can address 32,768 DMX-512 universes, equivalent to 16 million DMX channels.
The User Datagram Protocol (UDP), which manages data transfer, provides a transmission service with no handshaking. As it does not need to set up a communication mechanism before it starts transmission, the actual data transfer can start more rapidly. Another advantage of UDP is that it provides a data integrity check by sending a checksum at the same time, enabling the detection of transmission errors. Internet protocol (IP) is used for UDP transmission.
There are certain hardware requirements for implementing the ArtNet protocol in a lighting fixture or in an associated device such as an ArtNet Node (ArtNet to DMX converter). The microcontroller should be TCP/IP enabled and have sufficient performance to manage the TCP/IP communication while simultaneously transmitting several DMX universes. If it is controlling lighting directly, it should be able to generate several PWM outputs. The hardware requirements will naturally vary depending on the application in question.
The technical lighting team at Silica is available to assist customers with the implementation of this protocol and with the selection of the right hardware and software. In addition, demos for ARM Cortex M architectures are available to application engineers.
Well-known microcontroller makers, such as NXP, STMicroelectronics and Texas Instruments, provide controllers that come with a MAC, the appropriate TCP/IP demos and free-of-charge stacks. The most frequently used stacks are probably lwIP (at https://www.sics.se/~adam/lwip/) or µIP (at https://www.sics.se/~adam/old-uip/), which both support UDP communication. This saves developers time because they do not need to worry about the TCP/IP protocol first. They can use one that is already available and add the ArtNet protocol right away. When a certain string sequence is received, the dimmer data are filtered out and processed further.
An ArtNet-enabled device should facilitate configuration by enabling users to make settings on it. The easiest way to achieve this is with simple DIP switches, or – in a more advanced version – via TCP/IP and an embedded website. This would allow users to make settings for IP addresses or the DMX universe.
Of course, ArtNet can also be used to control individual lighting fixtures directly. If this is required, inexpensive ArtNet nodes that include an integrated DMX decoder can be directly implemented on a single microcontroller.
From the host perspective, there are already multiple applications for Windows, Apple and other platforms.
Apps that support the ArtNet protocol are also available for the iPhone and iPad. These help make this protocol suitable for all types of lighting. People could even control individual lights in their house from the comfort of their sofa by simply using their iPhone and home Wi-Fi network.
About the authors: Klaus-Dieter Kern is Senior Account Manager Silica Lighting & Demian Weber is FAE, Silica Lighting
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