RSGC ACES: Charlieplex Equalizer/Messager (Spring 2021)


The latest entry in the RSGC ACES' long and fascinating relationship with LED display circuitry is the Charlieplex Equalizer/Messager. Recent hardware, software, and design advances within our program led to the creation of this representative device. The domain details of the project are summarized below.

One aspect of the project I found interesting was the USB power/charger cubes that were sourced and tested. I went through a number of options from Amazon and had to return a number of styles because they were simply too noisy. This characteristic is clearly not something most users care about (judging by their Amazon reviews) but the upper range of the frequency spectrum the onboard Mic and MSGEQ7 IC picked up, contaminated the display. This shortcoming surely curtails their efficiency. Again not something one is likely to read in feedback, but it should be a concern to everyone, given the state of the planet.

By way of example, two video clips are provided below that highlight the noise levels of two chargers. In the first video (this one is not recommend), you can see the high frequency noise picked up by the microphone in the over 6 kHz range for this unit,

Video clip #1 (The Spencer Davis Group, Gimme Some Lovin')

In the second video (this one I do recommend), the acoustic data suggested better filtering,

Video clip #2. (Canned Heat, Dust My Broom)

You can get efficient chargers for well under these prices but I also wanted an esthetic match for the display. So, at the least, it had to be black.


HARDWARE features include,

SOFTWARE features include,

DESIGN features include,

C. D'Arcy. March 2021.