What is a Null Pixel and do I need them? Last Updated: 01/08/2018
We will occasionally get a question about why HolidayCoro doesn't sell a "null pixel" product or when a null pixel is needed for a project. This article covers those common questions we receive about Null pixels.
Q: What is a Null pixel? A: A null pixel is simply a normal pixel, of the same protocol and voltage, that is inserted into a and extension wire before or in the middle of a string of pixels to repeat the data over a longer distance.
Q: What does a Null pixel do? A: In pixels there are two lines of power going from the controller to the pixels - the first is the power for the pixel itself, typically 5 or 12 volts. The second is the data line (and sometimes a clock line) that transmits the pixel data and is typically 3.3 to 5 volts. As with all power circuits, as the length of the wire gets longer, the ability of the power to go down the wire decreases. For example, power output to string of pixels might start at 12 volts and by the time it reaches the end of the string it has dropped to 9 volts. When the power drop occurs for the power going to the pixel lights, this typically results in altered output - this is why white pixels can sometimes appear "pink" or "brown" as the length increases (see the video below). The exact same thing happens to pixel data which is also just a power circuit but with the data, the typical voltage is lower than the pixel and this results in either insufficient power and "volume" for the signal to reach the next pixel or corruption of the data along the way due to a poor signal to noise ratio. This drop in power then results in pixels that do not work at all after a long run of cable, typically 15 to 25ft between pixels or flickering. There are many other factors such as external EMI, wire quality, distance, voltage of the pixel, etc ultimately affect the distance which is why there is not defined length between pixels. How a null pixel "fixes" this is it takes the higher (typically) voltage from the power line and "repeats" the signal so that the signal is again amplified as it goes down the line to the next pixel.
Q: Does HolidayCoro sell a Null pixel? A: No, we do not sell a manufactured Null pixel product for the following reasons:
Installations that involve a Null pixel typically are highly customized, often these are house outlines. As each installation is unique, the location and number of Null pixels is also unique and thus customer made Null pixels typically are a better fit.
We do not design for projects that require Null pixels. When we design house outlines and other custom projects, we always design for 25ft and under of extensions. This is easier for customers to manage and understand how to assemble.
A Null pixel isn't a magic bullet. Just because the data signal can be amplified in a run doesn't mean that there will be sufficient power after a long run of extensions for the lights to actually work properly. So sometimes a customer needs a Null pixel only to have to run additional wire to power inject and if that is the case, then it didn't really solve any problem as it likely would have worked better to place a direct run of pixels from another controller.
Q: How do I make a Null pixel? A: Since a Null pixel is nothing more than a normal pixel already used on the same string (same voltage and protocol) along with typically setting the Null pixel option in a controller, to make a null pixel, just consider the following:
Will there be sufficient power AFTER the extensions and jumpers to run the pixels? This varies highly by pixel string, wire type, wire lengths, etc.
Does the string work without a Null pixel? We recommend mocking up your string with the same cables, pixels and controller and testing prior to assuming a null pixel will be required. This will also help answer the question about sufficient power also. Be sure to test with all pixels on in white output as this will be the worst case.
If it is determined that a Null pixel will be needed, simply locate the needed distance between the controller and the pixels, typically around 15 to 25ft, and cut the wire and solder in a pixel. Of course make sure to watch for pixel direction. This video show how to do that: