LED Flicker - Learning Objectives

1. What is light flicker?
2. How to avoid flicker?
3. what causes LED problems with flicker?
4. Is flicker acceptable?
5. Why does flicker seem to be different for individuals?

What is causing all this flickering of lights?

Since LED light sources do not mimic daylight, there is a need to have some metrics for comparison to familiar light sources of sunlight, incandescent and halogen.
​Flicker is a difficult challenge

Mate your LED with the correct driver and dimmer!

LED's require a driver. A driver is a current controlling device that is similar to a transformer. The driver converts 120 volt power to a lower voltage that is comfortable to the LED light source.  
Since LED's are tiny electronic chips, they are very sensitive to changes in electrical current.
If you try to dim an LED light with the wrong kind of dimmer, you may get flicker, or the light will got to zero more quickly than desired.
Manufacturers have been working hard to solve this problem. The solution is to 'mate' the LED + driver + dimmer in a pre-tested configuration that has been tested to provide smooth dimming.

Flicker Solutions

DC power supply may not flicker.
Magnetic dimmers may not cause flicker because they do not 'cut' the shape of the wave of current where you have 'blanks' and 'peaks' in the sine wave curve, that cause flicker.

Flicker

"Flicker is a rapid variation in light source intensity, usually most noticeable in peripheral vision.  Individuals vary widely in flicker sensitivity.  Almost all lighting systems produce some flicker, but most people are ale to tolerate minor fluctuations in light output over time.  More -severe flicker can contribute to headaches, photosensitivity, epileptic seizures, and other health issues.  Even if the flicker cannot be consciously detected by an individual, it may still affect the person neurologically." [3]

Lighting Facts - Comparing the numbers

• Lumens Per Watt = Efficacy of light source
  
• Watts = Power Consumption
• CRI = Color Rendering Index
• R9 = Red light component
• CCT - Correlated Color Temperature -K = Degrees Kelvin, or color temperature of the light
• Flicker = dimability and stability
• TM-30 = New Color Rendition Metric by IES

DOE - Department of Energy
Lighting Facts

 LED = Light Emitting Diodes - now the standard for new construction in the state of California, mandated by Title 24 energy code power limits, the most restrictive power allowances in the world, preceding adoption of similar codes worldwide. LED bulbs (or lamps as the lighting industry calls them, or Light Engines as the lighting designers call them) are inherently color biased. Since the Blue White chip was developed for the commercial market, manufactures have been struggling with achieving balanced white light.  A combination of coatings, voltage, age, and manufacturing processes all affect an LED's spectral and lumen output, industry terms for color and brightness.
Good lighting design should always include analysis of color rendering, light intensity, beam spread, flicker, and glare.

Related Topics

Manufacturer's Educational Links, LED for your B&B, Color in Paint - Why they Fade

Footnotes

1. Professor David Heeger - Light/Dark Adaptation
2. www.lightingfacts.com
3. IES RP-28-16 Seniors and Low Vision http://www.ies.org/
   

Photo Credits

• Lighting Facts Card - DOE - Department of Energy
• Test Colors for CRI & Light Source Color Rendering Chart - EYE Lighting
  
• TM-30 Test Colors - IES TM-30-15 Errata

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