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Varsha Raghunandan - Jul 27 2021

Dimming and DALI 101

What is dimming?

Dimming operation is engineered to change the brightness of an LED fitting as determined by an external intervention. Dimmable lighting is a great way to save energy and electricity costs. It also means that you can install the same fitting in multiple spaces and applications, dimming the light where necessary. Dimmed lighting also achieves an atmosphere of ambience, relaxation, and comfort.

There are two main types of dimmable drivers, pulse width modulation (PWM) and constant current reduction (CCR):  

Pulse width modulation is when the driver modulates the voltage supply to the LEDs by switching between on and off at a very high frequency. By adjusting the ratio between the lengths of the “on” and “off” pulse, the driver is able to control the level of light output. This dimming method allows for a broad dimming range and has the capability to decrease light output values to less than one percent. However, since it involves rapid switching, it requires sophisticated and expensive drivers to prevent perceptible flicker or buzzing noises.

Constant current reduction is a more simple and cost-effective dimming method. This involves a constant power supply to the LEDs, which is adjusted based on the light output requirements. This method allows you to situate the driver remotely from the light source. However, this method is not able to dim lights to less than ten percent.

Two main types of dimmers:

Leading edge dimmers cut from the first phase of the AC waveform. This means that when it turns voltage supply back on, it is at the peak of the waveform of the mains voltage. This can produce spikes in the current, which may cause dimmed luminaires to buzz and add stress to the driver. This type of dimmer usually has a high minimum load, which makes it an unpopular choice in modern lighting.

Trailing edge dimmers cut from the latter portion of the AC waveform. This means it turns back on at the zero level of the waveform of the mains supply. This allows the voltage to rise naturally with the mains supply. Therefore, it does not produce spikes and will not cause any of the buzzing that leading edge dimmers may produce. The trailing edge dimmers have a soft start, smoother lighting control, and are silent running. These dimmers are typically used in residential applications or smaller-scale commercial applications.

What is DALI?

In larger scale commercial environments, lighting is usually controlled with dual-function drivers that incorporate their own dimming capability. This is the DALI control system.

DALI stands for Digital Addressable Lighting Interface. The DALI system allows control and 2-way communication between the various components in a lighting plan. 

The DALI system is comprised of five main parts: 

  • Power Supply Unit: This maintains the bus voltage at the required level.
  • Application controller: This is the brains of the system. It picks up information from the input devices, and issues commands to the LED drivers.
  • Input devices: These are sensors or switches which detect movement or light level and communicate to the application controller.
  • The wiring: These carry the control signals and commands between the various components of the system.
  • Control gear: These are the drivers that receive commands from the application controller, and provide or adjust voltage supply to the LED chips accordingly.

The DALI system can also be used to create scenes or groups. 

Scenes in DALI involves the control gear (the LED drivers) remembering past settings for brightness. Each driver can remember up to 16 lighting presets. The application control then signals for each device to run a particular scene, and the control gear perform these preset actions accordingly. 

DALI groups is a concept that allows you to calibrate multiple LED fittings so that they operate as one unit. This way, you can group together lights in a particular room so that they all receive the same command and operate in unison.

To have more controlled and versatile lighting for a range of applications, get started with dimmable lighting! Check out Elekzon’s push-button trailing edge dimmer here 

To find out more about the DALI system, visit: https://www.nvcuk.com/technical/what-is-dali-/460.htm

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