Thursday, June 25, 2015

Project Edge Lit Sign - PART 2

The Electronics

This part of the project took me a bit longer than I expected.  I thought I had everything figured out for the design, parts and programming for the micro controller (Arduino Pro Micro) but ran into an unexpected issue that forced me to change course and use completely different hardware along with software libraries I hadn't used before.  Good news is that even with the changes and learning new hardware and software the new setup is actually easier and simpler to wire up and use.

My initial electronic design for controlling RGB LED's for the sign illumination.
  • 5mm RGB Common Anode LED's 
  • TLC5940 shift registers 
  • Arduino (Nano on breadboard)
  • Resistors for setting current limit
I built up the circuit on a solder-less breadboard to get it working.  Below is the setup from the Arduino Playground.

Wiring for TLC5940
Pictures of the layout:

I transferred the circuit to perf board (laid out the same as solder-less breadboard), cut and drilled out a piece of wood to mount the LED's in my box and wired in a wall wort for power.

All the Parts
Perf Board (back side)
Wiring it all up
Software library, further instructions, etc can be found at:
  1. Direct link to Google Repository
  2. Arduino Playground page for TLC5940
 So, after all that work building and testing - it worked perfect but it just wasn't bright enough for the sign so I had to reboot and go a different route.

Decided to go with Neopixels - much brighter RGB LED's.  Individually addressable for color and brightness, much easier to wire up - just a 3 wire connection to Arduino (Trinket or clone).  Do need real basic power filter (1000uF 6.3v or higher electrolytic capacitor across power rail to filter out spikes) as well as current limit to data line (300 to 500 ohm resistor to keep current at set level).

Currently there are 2 very good libraries (that I know of) for controlling Neopixel's with an Arduino.  I provided links to them as well as guides to using them below.

Adafruit Neopixel
I'll complete this post tomorrow (Part2b) with the final electronics and code.