Types of Dimming


There are 4 general types of analog dimming methods used for lighting:

-0-10V (or 1-10V)

-PWM Dimming

-Leading Edge 

-Trailing Edge


0-10V Dimming


0-10V dimming applies a DC voltage (DC) between 0 and 10 Volts to produce light at varying intensity levels. At 10V, the lights controlled by the dimmer are at 100% brightness. At 0 Volts, it either turns the lights off or has the lights dimmed to the lowest possible level and a switch is required to turn the lights completely off.
0-10V dimming is one of the most common dimming methods in commercial lighting today. This protocol is described under the IEC standard IEC60929 Annex E


Casambi CBUs that are able to control 0-10V dimming include:

-CBU-ASR

-CBU-A2D

-CBU-ARP

Other Casambi ecosystem products that control 0-10V dimming are available.



PWM Dimming (Pulse Width Modulation)


PWM is a dimming method that is commonly used with LEDs that use constant-current drivers. This technique works by adjusting the duty cycle of the current, resulting in changes to the average current in the string. PWM is effective for accurate light dimming requirements, as it can handle high dimming ratios at 100 Hz (high frequency, so that the human eye cannot detect the flickering effect), with minimal effects to the LED color/color temperature. To achieve dimming, the LED is toggled at a very rapid rate. For instance, at the highest setting (full output), the LED stays “on” and is never toggled. At 75 percent dimming, the lights are only “on” 25 percent of the time. 


The Casambi CBU-PWM4 is commonly used for PWM dimming and can control 10+ different types of LED using different profiles, selectable in the Casambi application.


Leading Edge Dimming


The leading edge is traditionally used with incandescent lamps and iron core transformers in connection with the dimming of halogen lamps. Leading edge creates a quick, stable voltage on the circuit. This also stabilizes the current in the circuit directly to the light source.
The leading edge dimmer is not as silent as the trailing edge dimmer, depending in particular on the quality of the dimmer and whether it is loaded above the prescribed minimum load.

This type of dimming is commonly known as TRIAC dimming for Forward phase dimming. 


Trailing Edge Dimming


Commonly referred to as (ELV), Trailing Edge dimming works similarly to leading edge by cutting the dimming signal but here, it will cut the dimming signal at the "trailing edge" of each cycle. 

The CBU-TED is used to dim this type of dimming. 



What is Dimming Resolution


Simply put, dimming resolution is the amount of output intensities of a luminaire while being dimmed. Normally a light is dimmed from 0% to 100%, but how many actually outputs are there within that range. This is what is referred to as "steps"; the amount of steps the output of the dimmer can provide is the dimming resolution. In Casambi's case, the CBU-PWM4 will provide 100 steps by default; although this value can be customized for certain installations.



Linear vs Logarithmic Dimming


In most scenarios, dimming of a luminaire goes in the following order:

Dimmer - Driver- Luminaire


The dimmer tells the driver to dim the luminaire, but the question is, what scale do the dimmer and driver use to communicate with the 3 pieces of hardware at play?


The ultimate goal is to ensure the desired output of the dimmer matches the output of the light; so if the dimmer says 25%, 25% of the light is being output and when the dimmer says 75%, 75% of the light is output. 


The chart below shows the difference between a linear and log dimming curve. 


So how does the dimmer and driver effect the dimming of the luminaire:



DimmerDriverOutput
LinearLinearUndesirable Dimming
LogarithmicLogarithmicUndesirable Dimming
Linear Logarithmic
Desired Dimming
Logarithmic
LinearDesired Dimming



Dimming Types and Curves


So what does this mean for choosing a driver compatible with Casambi controllers? See the chart below for choosing the correct type of driver with the applicable Casambi dimmer.


Casambi CBUsDimmer CurveDriver Choice
CBU-PWM4
Both
Either
DALI (DCS, A2D, ASD)LinearLogarithmic
0-10V (ASR, A2D, ARP)LinearLogarithmic
Other Ecosystem ControllersVaries