Which Pixel Chip?

It was my intent to place on this page a table comparing all of the different pixel controller types. However, most of the data sheets are incomplete, so there will just be some discussion on the desired characteristics.

Current Tolerance

The number one specification to review for a pixel controller would be the accuracy of the current for each of the outputs. The LED’s brightness is proportional to the current, so you want the current to be consistent for all of the LED outputs. Sadly most of the parts do not specify this tolerance. There are a few that  actually mention the value and it is either the nominal value or the worst case (1% to 1.5% nominal to 6% worst case).

LED Matching

The data sheets for most of the RGB pixels do not specify the light color of the LED’s. I would want a LED’s where the brightness and color match between device to devices. Of the few manufacturers that I have perused, Cree is the only company that allows you to buy their LED’s with the colors matched.

Protocol Speed

Most of the LED’s run at 800Khz data rate, which is fast enough to output 150 pixels in 5mS. The only concern with protocol speed would be if you are running hundreds of them in series. Also, the refresh rate varies between all of the pixels varies from about 400 to 1600 hertz. This really does not matter for most people, unless you are spinning one line of pixels and trying to draw a 2D display. If this was the case you would want the fastest rate available. I used the WS2812B for the Christmas ornament, and had to lite two at a time to reduce the flicker, since they run at 400Hz.

Conclusion

Since there is little information on each of the pixel controllers, I would tend to choose one of the more popular types. This will ensure that from year to year you will be able to continue to  buy your pixel of choice.

 

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