Espressif

Espressif LED Fan Solution

In recent years, "LED fans" have become a common sight in large shopping malls or events. These devices resemble regular fans but can display a variety of patterns when they spin, with some even capable of showing dynamic 3D patterns. They are striking and often captivate attention, serving as effective tools for promotion and advertising. So, how do these LED fans display patterns?

Strictly speaking, these "fans" are more accurately described as "rotating LED light strips," and their professional term is "holographic 3D smart display." When powered on, the "fan blades" begin to spin, creating a series of 3D images that appear as they rotate, providing a vivid and realistic display. The LED fan can effectively hide its blades depending on the size and color of the patterns because there are no visible borders or fixed screens, making the dynamic images appear as if they are floating in mid-air, creating a highly realistic effect.

The 3D smart display not only leverages the hardware of rotating LEDs but also takes advantage of the human eye's persistence of vision phenomenon.

For the rotating LED hardware, the concept is straightforward: by calculating the rotation speed of the "fan blades," the frequency at which the LEDs change is determined. Different LEDs are lit at various times, creating different patterns.

The persistence of vision phenomenon refers to the brief period during which visual images remain on the retina after the light stimulus has ceased. When observing objects, light signals are transmitted to the brain, and there is a short delay before the image disappears. This residual visual effect, lasting about 0.1 seconds, is known as the "afterimage," and the phenomenon itself is called "persistence of vision."

Typically, a fan's blades are equipped with one or more series of LED lights. For simplicity, let’s assume there are 20 LEDs arranged from the center of the fan to the edge of the blades, numbered from 1 to 20. To illustrate how this works, assume the fan rotates at 600 RPM (revolutions per minute), and at 0 seconds, the LED lights are positioned at 0 degrees directly above the fan.

To display the time "6:00" on the fan, the minute hand should point straight up, and the hour hand should point straight down. This would require the following:

At 0 seconds, LEDs 1 through 20 light up to show the minute hand.

At 0.05 seconds, LEDs 1 through 10 light up to show the hour hand.

At 0.1 seconds, LEDs 1 through 20 light up again to show the minute hand.

At 0.15 seconds, LEDs 1 through 10 light up again to show the hour hand.

This pattern continues, creating a complete visual effect of a clock reading "6:00" due to the persistence of vision. For more complex patterns, the LED fan uses a more sophisticated structure and programming.

Currently, 3D smart displays are primarily used for advertising due to their editable nature and stunning visual effects. With the increasing adoption, these displays are expected to find applications in more areas in the near future.

Espressif's MCU, with built-in Bluetooth (BT) and Wi-Fi capabilities, can control the fan and convert images to LED display matrix data. The combination of Wi-Fi and BT allows users to transfer the content displayed on the fan remotely via smartphones. Using Espressif's main control unit enables a more compact design and reduces costs.