LED Technology
in the wireless ecosystem. The gateway contains a DALI application controller that connects to devices in the wired DALI network. The DALI Alliance has published two gateway specifications to cover wireless- to-DALI gateways with either Bluetooth mesh (Part 341) or Zigbee (Part 342). Other protocols may be supported in future. The same certified DALI drivers can be used with either Bluetooth or Zigbee.
The DALI devices are automatically discovered and addressed by the gateway, before joining the ecosystem network. Security is ensured via the existing features of Bluetooth mesh or Zigbee.
In operation, the wireless devices talk to the gateway using their existing protocol (Zigbee or Bluetooth). They can control light output and fading of DALI devices via the gateway, and can read lamp failure information from the DALI devices, as well as selected data such as energy usage and diagnostics data. Application controllers in the DALI network cannot control, configure or query devices in the wireless ecosystem. This means that the wireless ecosystem is effectively in control, and the DALI system is subordinate.
Figure 3: DALI+ enables devices to communicate using existing DALI commands carried over a wireless medium.
Using wireless and wired DALI together
In many systems, it may be necessary or preferable to combine wireless and existing wired DALI systems or luminaires. Figure 2 gives an example of the use of gateways: in this scenario, the office luminaires each have a gateway that forms part of the wireless network. In the corridor, a wired DALI line connects all the luminaires with a single gateway that also participates in the wireless ecosystem. Alternatively, for a system based on DALI+, a new type of device known as a bridge enables application controllers in the DALI+ network to
access and control the DALI wired control gear and control devices (Figure 3). Bridges link wired and wireless networks, using the DALI protocol throughout.
For more complex systems, a backbone such as Ethernet can be used to connect multiple wireless DALI+ systems. Additionally, DALI application controllers can support multiple subnets, which may be any combination of DALI+ and wired DALI subnets.
Conclusions
DALI is the established standard for digital lighting control systems. The DALI Alliance
now enables lighting system designers to work with wireless connectivity – giving them access to DALI’s lighting-specific capabilities, such as precise dimming and colour control, all backed up by proven, reliable technology and wide industry adoption.
The combination of wireless and DALI is designed to bring flexibility and control, enabling lighting designers to create new systems that are scalable, fully-featured, and cost-effective.
www.dali-alliance.org Source:
https://www.dali-alliance.org/daliplus/
Study offers new insights on improving blue OLED performance for displays and lighting
Scientists at the National Physical Laboratory (NPL) have collaborated with the Samsung Advanced Institute of Technology (SAIT) on a new study (
https://www.nature.com/articles/s41467-023-43840-9) to better understand the degradation of blue organic light-emitting diodes (OLEDs).
T
he degradation mechanisms - whether physical, chemical or something else - that cause blue OLEDs to fail are still not yet fully understood. This limits the stability of blue OLEDs - and by extension the lifetime of OLED technology in full colour display screens and lighting. The first polymer light-emitting diode (PLED) was created at NPL in 1975. It used a polymer film of up to 2.2 micrometers thick located between two charge-injecting electrodes. Since then, developments in red and green OLED technology resulted in these coloured OLEDs being now comparable to conventional LEDs.
Understanding the degradation mechanism of blue OLEDs is essential to improve their performance and stability. However, OLEDs are formed of very thin layers of organic molecules, and chemically sampling nanoscale
www.cieonline.co.uk
depth resolution within the OLEDs multi- layered architecture.
Picture credit: NPL
organic layers and interfaces with enough analytical information is challenging. To tackle this longstanding problem, the NPL / SAIT team used OrbiSIMS, a mass spectrometry imaging technique invented
at NPL in 2017. The team used OrbiSIMS’ nanoscale mass spectrometry to identify, for the first time, degradation molecules of blue OLEDs with unprecedented sensitivity and localise them with seven nanometres
The team found that chemical degradation is mainly related to loss of oxygen in molecules at the interface between emission and electron transport layers. The OrbiSIMS results also showed approximately one order of magnitude increase in the lifetime of OLED devices that use slightly different host materials. The results and the method described in the study can inform and drive future efforts on improving the performance of new blue OLED architectures and help display technology manufacturers to develop better quality displays with longer product lifetimes. The method has already been used in another study led by Samsung and the Korea Advanced Institute of Science & Technology (KAIST), which also published in Nature Communications.
www.npl.co.uk Components in Electronics February 2024 45
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