Binary Burst LED balancing

I’m working on a new clock design. I’m not ready to talk much about it yet, but I did order a couple of different LEDs for it. I need blue LEDs and red/blue bicolor LEDs where the blues match each other. I wanted 5mm diffused parts and was able to find them, but not both types from the same vendor. The parts just arrived and above you can see me testing them out.

They’re incredibly bright! In fact, I have to run them at a pretty low duty cycle for them not to burn your eyes out:

  • Blue LEDs at 1/16 duty cycle
  • Red LEDs at 1/4 duty cycle

I’m driving them all at 10ma. You can see that the bi-color produces a nice magenta color. One unexpected phenomenon is that there is a blue halo around the bicolor LED. It must have something to do with the wavelength and the curved dome of the case. Oh well, this will only happen a few times per day so it doesn’t worry me.

More on this clock as I get further into the development process.