Understanding the scan mode of a led wall screen

The scan mode of a LED wall screen can be an important parameter to choose between several tiles. The scan mode has indeed an impact on two parameters of your screen: the light perception and the electric consumption. It must be associated with a third parameter, the refresh rate which, if high, can compensate for a low scan ratio.

There are several modes of scanning: static mode, 1/2 scan, 1/3 scan, 1/4 scan, 1/8 scan, etc.

What is the scan mode can of a led wall screen?

Principle Simplified: Each micro controller has a number of pins and can drive up to the same number of led chips. Each chip manages a led line. The scan mode determines the ratio of the number of lines of led piloted simultaneously to the total number of lines of each module.

Let’s take a concrete example: a module of 144 led divided into 12 lines of 12 led. A controller will control this module according to one of the scan modes.

When the module is off, no LEDs are lit. The controller does nothing.

Static mode: The controller manages all lines at the same time. All led lines are on at the same time

Mode 1/6 scan: the controller manages 1/6 of the module lines at the same time, or here, 2 lines out of the 12. 

When it comes to our screens, all the lines should be lit.

When one looks at the screen with the naked eye it is actually the impression that emerges. But in reality this impression is due to our retinal persistence because only 2 lines out of the 12 are lit simultaneously. However, the refresh rate of a screen is always higher than the capacity (speed) of perception of our eye.

If the sweep rate was reduced enough, we would not see the module turned on but we would see scrolling separately the lines as in this animation .

1/4 scan mode: the controller manages 1/4 of the module lines at the same time, ie 3 lines out of 12.

Mode 1/2 scan: the controller manages half the lines of the module at the same time, ie 6 lines out of the 12.