LED matrix sign board

Using arduino and MAX7219 LED matrix panels daisy chained could make an interesting carousel LED sign board. In order to promote MakerClubQUT, I linked up 3 4-8x8 panels together to display scrolling information. See below.

An Arduino Nano is used to control this LED panel. Using the MD_MAX79xx library, a number of scrolling texts and animated objects are programmed. At the end of scrolling information, if there is no one there to see, the information will stay as a bouncing dot going left-to-right and right-to-left forever, until when someone (movement) is detected by the included PIR sensor. As can be seen in the picture and video above, a PIR sensor in included to trigger the information carousel from the start.  A red LED is also used to indicate when the PIR sensor is triggered.  The casing can be 3D printed from this TinkerCad project. The arduino codes can be downloaded here. 

One issue with this project is the limitation of PIR sensor, which utilises infrared to sense movement. However, infrared cannot go through solid objects so when this is placed behind glasses, it will not be able to sense any movement.  

To overcome this, another version of this LED sign board is created to incorporate the RCWL-0516 microwave sensor. This microwave sensor emits microwave omni-directionally, which can also penetrate wall and glasses. This RCWL-0516 sensor's microwave is safe and is designed to detect quite specifically human movement.  With this version, I could then place this panel inside a classroom on a window pane, and people who walk pass could trigger the scrolling information to get their attention.  See pictures below:

As can be seen in the right picture above, a clip wire-connector is used to provide USB power directly into the 5V and GND pins. This may not be a good practice, but works well in this project perhaps due to the power consumption is not too high from the MAX7912 panels.

The casing is different from version 1 and can be downloaded in this TinkerCad project. The Arduino codes can be downloaded from here.