Saturday, July 4, 2009

Simmons LED Display Part 2: Hardware Implementation

I chose to use the Arduino microcontroller for this project for many reasons. They're relatively cheap, easy to program and even easier to use. You literally just plug the device into your computer via a standard USB cable and you're ready to program. The Arduinos each have 14 total I/O pins, two of which are used by the onboard serial communications chip. This means you have 12 free pins to play with on each device, if you still want to communicate with a computer.

I needed 36 total pins (6 by 6), and I wasn't confident enough to try to learn how to build a multiplexing circuit, so I just decided to use multiple Arduinos. This made even more sense considering I needed to light up LEDs on multiple floors of my building, and wanted to avoid long cable runs. For symmetry, I bought 4 Arduinos, to have 2 on each floor.

After several unsuccessful attempts to make the power boards on Radio Shack stripboards, I finally discovered Winford Engineering. They carry excellent prototyping products. Some pictures of the completed power boards are shown to the left. Each power circuit is just one MOSFET and one 2 Ohm Resistor. The Digikey part numbers I used are: IRFZ14PBF and 23J2R0E. The schematics are coming soon.


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