Jim Wink's Make Blog

As I mentioned in my previous post I was a bit worried that my accelerometer wasn't working properly. When hooked up along with an LED matrix there were some LEDs that just wouldn't light. It seemed like was the X-axis that was giving me trouble.  Since I'd " played with it " I couldn't return it to Sparkfun, in any case it was past the 14 day limit. This is kind of a bummer because it cost me about $20 - aside from the Arduino, one of the most expensive components in my inventory. So, I decided to create a way to test it. I figured it'd be cool to find out if there was actually a range of values that the X-axis wasn't producing. To do this would involve having the Arduino read the 3 axis and output the values through the serial port. I'd then have to write some software on the other side to read the values and display them in a way that made sense.  First I hooked everything up on the Arduino and  proto-sheild (see image). Then I proceeded to writ

One of the last items I decided to try out from my first order from SparkFun was a medium sized LED matrix . This is an 8 by 8 (64) grid of LEDs that are multi-color. Send voltage through one set of pins and you get green, through another set and you get red - through both I think yellow. The specifications  claim some pretty specific levels of voltage and current. The green wants 3.3 volts and 20 mA, the red wants 2.0 volts and 20 mA. The Arduino Duemilanova puts out 5v and 40 mA for the most part, though it has one 3.3v pin that produces 50 mA.  Of course, when I started playing with it I just through 5v and 40 mA through everything trying to see what it was capable of. For a while this seemed fine, but after a bit it some of the LEDs stopped lighting, or some light when not sent current. It still works, for the most part, with a few obvious gaps. I did remember later that the Arduino can do Pulse Width Modulation (PWM) through some  of it's digital out pins: 3, 5, 6, 9, 10, an