How To Determine The Distance Between The Ceiling Fan And The Downlight To Avoid Strobing?

By | February 25, 2024

If you check by internet how to avoid strobing in your house, you probably get a lot suggestion of minimum distance gap between the ceiling fan blade tip and the downlight. But how to accurately determine the minimum gap with a proper method?

Basically, to avoid strobing, the fan blades have to avoid the path of the light emitted from the downlight.

To calculate the minimum distance between a ceiling fan and downlights to avoid strobing , you can use a simple mathematic trigonometric formula to find it out.

how to determine the distance between the ceiling fan and downlight

Refer to the above diagram:

Identify the Angle of Light Spread (θ) : Determine the angle of light spread provided by the recessed light fixture. This angle typically represents the cone of light emitted by the fixture.

Determine the Height of the Fan (h): Measure the distance from the ceiling to the tip of the ceiling fan blade. This will be the height of the triangle formed between the ceiling, the tip of the fan blade, and the recessed light.

d=Minimum distance from fan blade tip to downlight to avoid strobing

tan (θ/2) = d/h

d = h x tan (θ/2)

For example, light spread angle 30°, height of the fan from ceiling 50cm.

Example - how to determine the distance between ceiling fan and downlight

d= 50 x tan15°

d= 50 x 0.2679= 13.40cm


So, in this example, the minimum distance from the tip of the fan blade to the downlight should be approximately 13.40 inches to avoid strobing effects.

This calculation ensures that the light emitted by the downlight will not interfere with the spinning blades of the ceiling fan, minimizing the potential for strobing effects.

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