How to choose the right dimming curve?

Whether commercial applications or residential buildings, dimming has a crucial role in meeting the diverse visual needs and energy savings.  With technological advancements, most of the lighting controllers  offer smooth transitions, which is an important prerequisite! But, how is it possible when the human eye perceives light in a logarithmic manner? Is it because of the way controllers, drivers or fixtures are made? If so, are all control devices made equal?  

Well, No! Not all controllers are created equal. Then? 

Let us discuss certain facts that really matter!  

We will start with dimming curves 

Dimming curve is the configured voltage output as a response to the control signal input. For ex: when you want to dim the lights, you will change the slider position, which is the input signal. The controller will send this input signal to the driver. The driver will convert this electrical signal that powers the luminaires. 

Electrical signal flow between controller, driver and Luminaire
Image: Electrical signal flow

The light output level or dimming performance is determined by the working of the dimmer/controller, driver and the the human eye. Hence, configuring the system appropriately is an important factor that determines the performance of your lighting network. The functioning of the human eye is not as simple as it seems to be! The eye doesn’t perceive light level changes in a linear fashion. This means, there is a clear distinction between actual, measured and the way we perceive the light intensity.  

You might have heard about the measured and perceived light, haven’t you? Let us know how important it is! 

measured and perceived light
Image depicting measured and perceived light

By enlarging the pupil, the human eye responds to low light levels and that allows it to see more light. For example:  if the measured light output is 1%, then the perceived light level will be 10%.  For the brightness of the luminaire to be matched to our eyes, the dimming curve has to be configured appropriately. If not the perceived changes in brightness will be affected.   

Now, this will answer you why choosing the right dimming curve is important.  

The dimming curve provides the option to set the dimming behavior as per the human eye functionality and application preference. So, if you want a 50% reduction in the light intensity, you need to select the expected dimming response !  

What are the different types of dimming curves? 

We have discussed the importance of selecting the right dimming curve.  

There are different types of dimming curves. The two significant types of dimming curves we will discuss are linear and logarithmic dimming (sometimes referred to as “square-law”). 

In linear dimming curves the brightness output is linear when compared to the input value. If the input signal is 25%, then the output value will also be the same. However, in the logarithmic dimming curves the input values change with the dimming levels. At the deeper dimming levels, the signal to the driver changes slower and at the brighter end the signal will be faster. 

You can make a dimmer (input device) or a driver (output device) that follows your own custom curves like “S” curves, “soft linear” curves, and so on. These are usually made to provide you more control over specific areas of the input range (i.e., “slider”). Manufacturers of architectural products, on the other hand, are more likely to use “linear” or “logarithmic” for both input and output devices, which provides you the greatest results. 

The image below depicts the dimmer position and output light level in different dimming curves. 

Types of Dimming
Image: Types of dimming curves

Which is the appropriate dimming curve for 0-10V? 

The 0-10V dimming curves are not yet standardized. As a matter of fact,  most of the 0-10V dimmers are linear. If the dimmers are linear then the driver should have a logarithmic dimmer. On the other hand, if the dimmers are logarithmic then the drivers should use linear or soft-linear dimming curves. 

In this part let us discuss the factors that we should consider when choosing  the dimming curves!  

Can we use linear/logarithmic combination?  

A linear dimmer can be used with a logarithmic driver and vice versa.  

Both combinations get the same result.  

As previously stated, these combinations produce what is known as “square-law dimming.” This produces output that is changed according to how the eye perceives light levels rather than what the light meter reads.  

This combination makes greater use of the entire range of slider locations, particularly at the low end of the light output spectrum.  

 As a result, they’re usually intended to dim to 1% of total output, or even less in some circumstances. 

Can we use linear/linear combination? 

When dimming is primarily used to save energy, a linear/linear combination i.e., a linear dimmer paired with a linear driver – is usually sufficient.  

Drivers built primarily for energy efficiency are frequently dimmable down to 20% of full output (or in some cases to 10 percent ).

These are frequently advertised as “energy-saving” items.

Because the primary goal of employing these goods in that application is to save energy, the perceived light level does not always match the slider position isn’t a big deal. 

The below table gives you an idea of choosing appropriate dimming curve combinations!  

Dimming curve combinations
Image: Appropriate dimming curve combination

This is our final blog in the 0-10V blog series. In the first blog, we have discussed about  Basics of 0-10V and some interesting facts, and the   second blog 0-10V Wiring, we have detailed about the wiring practices. With this blog, i.e. Dimming curves, we are coming to an end to our 0-10V blog series. Hope you will find these blogs useful.  

Please comment your thoughts and feel free to reach us!  

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