Catsnap

Current Evaluation

Current Evaluation

Once my RGB LEDs arrived, I had to figure out the appropriate current for each color. The red is considerably dimmer than the green and blue, at least to my perception, so I couldn't just use the same resistor for all three colors. I also had to ensure that the entire array will draw less than 470mA—the USB standard allows up to 500mA, and the Teensy itself takes 30.

I settled on 4.5 mA red, 0.5 mA green, and 0.7mA blue. Even with 80% of the total current allocated to red, the color balance is still bluish, but it was the best I could do while maintaining acceptable brightness.

In my notes you can see that I had my first encounter with contact resistance in my breadboard. This became an increasingly frustrating problem as I started to add power-amplifying transistors to the circuit. Once I learned more about the math, I gave up entirely on trying to get meaningful readings.